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CJ5 misfires at high RPM/hard acceleration
Gentlemen,
I'm having some problems tracking this down. When I accelerate hard or get up to a certain RPM (about 3000) at cruising, I get popping coming out of my exhaust & a huge lack in power. The engine has never stalled, but I can't go any faster in that gear due to the misfiring. I've done almost everything that I can think of short of checking the timing chain & replacing the carburetor. Here's what I've done so far: Changed coil + ballast resistor + ignition wires/wire to distributor Changed fuel filter + replaced all fuel lines Changed fuel pump Changed points + condenser Changed plugs + plug wires (plugs gapped at .035) Changed cap + rotor Changed vacuum advance (this was confirmed bad & made a huge difference) The initial timing is 6 degrees BTDC & the dwell angle is about 31. I get about 16hg of steady vacuum at idle & about 7psi of fuel pressure at idle. The idle & even light acceleration is perfect, which makes me think it's not a timing chain issue, but I don't know enough about what the symptoms of a slipped chain would be to make that call. When the engine is at TDC of piston 1's compression stroke, the rotor lines up perfectly with cylinder 1's plug wire, which also makes me thing it's not necessarily a timing chain issue. Since I have changed the plugs & tried to further diagnose the problem, my plugs have turned black. This along with the popping in the exhaust obviously mean my mixture is either too rich, or something is going haywire with the timing & causing the fuel to not burn at higher RPM. One thing worth noting, is that I have not changed the plugs since they have been fouled since I replaced the faulty vacuum advance. I didn't know if this would make a difference or not & didn't want to risk fouling a new set while troubleshooting. I can literally get flames to shoot out of my exhaust if I abuse it enough. This happens on both sides & I have dual exhaust, leading me to think it's not a valve issue, unless I'm really unlucky & have a problem on both sides of the engine. The jeep is a recreational vehicle of sorts, used primarily to climb up & down sand dunes. The symptoms all occured when my fuel pump died about 2 years ago. After I replaced the pump, the engine started doing this. I've since replaced it again to rule that out with no change. I've also rebuilt the carburetor, but it was the first time I ever did such a thing, so it's quite possible I missed something. The accelerator pump works fine, the idle mixture screws are set very lean (since I think the mixture is too rich for some reason), the power valve has been replaced & I even checked it again last week & I can see spray coming out of the booster venturi when I rev the engine (it does this whether I'm moving or not). Another thing I noticed is that when the engine is cold, if I hold my hand in front of the exhaust, it sprays black fluid on me at idle. It's not a lot, but I noticed it when it was sprayed on my leg one day. It has no smell to it other than stinky exhaust, so I don't really know what this is. My coolant level has not changed noticeably, so I wouldn't think it to be a water leak, but I can't say with certainty. Here are the basics: 1972 Jeep CJ5 AMC 304 Aftermarket parts: Edlebrock peformer intake Holley 600cfm 4-bbl carb Edlebrock shorty headers Thanks for any help you guys can give on this. I'm at a loss & don't know what to do next. -Matt |
Re: CJ5 misfires at high RPM/hard acceleration
If the plugs are just fouled, I would pull them out and clean them up with
some light brushing and some B-12chemtool. Re-gap, re-install, and see if that helps. Carl <matthew.nye@gmail.com> wrote in message news:1184524973.150369.268860@22g2000hsm.googlegro ups.com... > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
If the plugs are just fouled, I would pull them out and clean them up with
some light brushing and some B-12chemtool. Re-gap, re-install, and see if that helps. Carl <matthew.nye@gmail.com> wrote in message news:1184524973.150369.268860@22g2000hsm.googlegro ups.com... > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
If the plugs are just fouled, I would pull them out and clean them up with
some light brushing and some B-12chemtool. Re-gap, re-install, and see if that helps. Carl <matthew.nye@gmail.com> wrote in message news:1184524973.150369.268860@22g2000hsm.googlegro ups.com... > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
If the plugs are just fouled, I would pull them out and clean them up with
some light brushing and some B-12chemtool. Re-gap, re-install, and see if that helps. Carl <matthew.nye@gmail.com> wrote in message news:1184524973.150369.268860@22g2000hsm.googlegro ups.com... > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
How is the gas tank air vent filter?
It will kill the top end and act very strange when this gets blocked. It is a $2.00 'emissions' filter on the bottom of the charcoal canister. To test this, just drive with the gas cap loose or off and see what happens. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) matthew.nye@gmail.com wrote: > Gentlemen, > |
Re: CJ5 misfires at high RPM/hard acceleration
How is the gas tank air vent filter?
It will kill the top end and act very strange when this gets blocked. It is a $2.00 'emissions' filter on the bottom of the charcoal canister. To test this, just drive with the gas cap loose or off and see what happens. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) matthew.nye@gmail.com wrote: > Gentlemen, > |
Re: CJ5 misfires at high RPM/hard acceleration
How is the gas tank air vent filter?
It will kill the top end and act very strange when this gets blocked. It is a $2.00 'emissions' filter on the bottom of the charcoal canister. To test this, just drive with the gas cap loose or off and see what happens. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) matthew.nye@gmail.com wrote: > Gentlemen, > |
Re: CJ5 misfires at high RPM/hard acceleration
How is the gas tank air vent filter?
It will kill the top end and act very strange when this gets blocked. It is a $2.00 'emissions' filter on the bottom of the charcoal canister. To test this, just drive with the gas cap loose or off and see what happens. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) matthew.nye@gmail.com wrote: > Gentlemen, > |
Re: CJ5 misfires at high RPM/hard acceleration
In article <1184524973.150369.268860@22g2000hsm.googlegroups. com>,
<matthew.nye@gmail.com> wrote: > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: Try driving with the coil "+" terminal jumped straight to the battery to eliminate the possibility that there is an amperage loss through the ignition switch. Also, the old fuel pump may have send diaphragm chunks into the carb. How well did you blow out the passages? I suppose it is possible that a pump seizing against the eccentric on a worn chain may have caused a tooth jump. If this is the original chain, it might be worth the time to change it anyway. > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > -- CobraJet |
Re: CJ5 misfires at high RPM/hard acceleration
In article <1184524973.150369.268860@22g2000hsm.googlegroups. com>,
<matthew.nye@gmail.com> wrote: > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: Try driving with the coil "+" terminal jumped straight to the battery to eliminate the possibility that there is an amperage loss through the ignition switch. Also, the old fuel pump may have send diaphragm chunks into the carb. How well did you blow out the passages? I suppose it is possible that a pump seizing against the eccentric on a worn chain may have caused a tooth jump. If this is the original chain, it might be worth the time to change it anyway. > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > -- CobraJet |
Re: CJ5 misfires at high RPM/hard acceleration
In article <1184524973.150369.268860@22g2000hsm.googlegroups. com>,
<matthew.nye@gmail.com> wrote: > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: Try driving with the coil "+" terminal jumped straight to the battery to eliminate the possibility that there is an amperage loss through the ignition switch. Also, the old fuel pump may have send diaphragm chunks into the carb. How well did you blow out the passages? I suppose it is possible that a pump seizing against the eccentric on a worn chain may have caused a tooth jump. If this is the original chain, it might be worth the time to change it anyway. > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > -- CobraJet |
Re: CJ5 misfires at high RPM/hard acceleration
In article <1184524973.150369.268860@22g2000hsm.googlegroups. com>,
<matthew.nye@gmail.com> wrote: > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: Try driving with the coil "+" terminal jumped straight to the battery to eliminate the possibility that there is an amperage loss through the ignition switch. Also, the old fuel pump may have send diaphragm chunks into the carb. How well did you blow out the passages? I suppose it is possible that a pump seizing against the eccentric on a worn chain may have caused a tooth jump. If this is the original chain, it might be worth the time to change it anyway. > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > -- CobraJet |
Re: CJ5 misfires at high RPM/hard acceleration
Sounds like it might be runing rich. the 600 cfm Holly is a lot of carb
for a 304 engine, at 3000 rpm you are only at about 1/3 of it's max flow. I'm no Holly expert so ask which jets the experts might suggest. Your vac advance was diagnosed as bad but how can you tell you fixed it correctly? If the total advance is not enough, you will get exactly the symptoms you mention. I'd try giving it another 5 degrees of intial advance, see if that changes anything. If it does, more distributor work is in order. matthew.nye@gmail.com wrote: > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
Sounds like it might be runing rich. the 600 cfm Holly is a lot of carb
for a 304 engine, at 3000 rpm you are only at about 1/3 of it's max flow. I'm no Holly expert so ask which jets the experts might suggest. Your vac advance was diagnosed as bad but how can you tell you fixed it correctly? If the total advance is not enough, you will get exactly the symptoms you mention. I'd try giving it another 5 degrees of intial advance, see if that changes anything. If it does, more distributor work is in order. matthew.nye@gmail.com wrote: > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
Sounds like it might be runing rich. the 600 cfm Holly is a lot of carb
for a 304 engine, at 3000 rpm you are only at about 1/3 of it's max flow. I'm no Holly expert so ask which jets the experts might suggest. Your vac advance was diagnosed as bad but how can you tell you fixed it correctly? If the total advance is not enough, you will get exactly the symptoms you mention. I'd try giving it another 5 degrees of intial advance, see if that changes anything. If it does, more distributor work is in order. matthew.nye@gmail.com wrote: > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
Sounds like it might be runing rich. the 600 cfm Holly is a lot of carb
for a 304 engine, at 3000 rpm you are only at about 1/3 of it's max flow. I'm no Holly expert so ask which jets the experts might suggest. Your vac advance was diagnosed as bad but how can you tell you fixed it correctly? If the total advance is not enough, you will get exactly the symptoms you mention. I'd try giving it another 5 degrees of intial advance, see if that changes anything. If it does, more distributor work is in order. matthew.nye@gmail.com wrote: > Gentlemen, > > I'm having some problems tracking this down. When I accelerate hard > or get up to a certain RPM (about 3000) at cruising, I get popping > coming out of my exhaust & a huge lack in power. The engine has never > stalled, but I can't go any faster in that gear due to the misfiring. > I've done almost everything that I can think of short of checking the > timing chain & replacing the carburetor. Here's what I've done so > far: > > Changed coil + ballast resistor + ignition wires/wire to distributor > Changed fuel filter + replaced all fuel lines > Changed fuel pump > Changed points + condenser > Changed plugs + plug wires (plugs gapped at .035) > Changed cap + rotor > Changed vacuum advance (this was confirmed bad & made a huge > difference) > > The initial timing is 6 degrees BTDC & the dwell angle is about 31. I > get about 16hg of steady vacuum at idle & about 7psi of fuel pressure > at idle. The idle & even light acceleration is perfect, which makes > me think it's not a timing chain issue, but I don't know enough about > what the symptoms of a slipped chain would be to make that call. When > the engine is at TDC of piston 1's compression stroke, the rotor lines > up perfectly with cylinder 1's plug wire, which also makes me thing > it's not necessarily a timing chain issue. Since I have changed the > plugs & tried to further diagnose the problem, my plugs have turned > black. This along with the popping in the exhaust obviously mean my > mixture is either too rich, or something is going haywire with the > timing & causing the fuel to not burn at higher RPM. One thing worth > noting, is that I have not changed the plugs since they have been > fouled since I replaced the faulty vacuum advance. I didn't know if > this would make a difference or not & didn't want to risk fouling a > new set while troubleshooting. I can literally get flames to shoot > out of my exhaust if I abuse it enough. This happens on both sides & > I have dual exhaust, leading me to think it's not a valve issue, > unless I'm really unlucky & have a problem on both sides of the > engine. > > The jeep is a recreational vehicle of sorts, used primarily to climb > up & down sand dunes. The symptoms all occured when my fuel pump died > about 2 years ago. After I replaced the pump, the engine started > doing this. I've since replaced it again to rule that out with no > change. I've also rebuilt the carburetor, but it was the first time I > ever did such a thing, so it's quite possible I missed something. The > accelerator pump works fine, the idle mixture screws are set very lean > (since I think the mixture is too rich for some reason), the power > valve has been replaced & I even checked it again last week & I can > see spray coming out of the booster venturi when I rev the engine (it > does this whether I'm moving or not). Another thing I noticed is that > when the engine is cold, if I hold my hand in front of the exhaust, it > sprays black fluid on me at idle. It's not a lot, but I noticed it > when it was sprayed on my leg one day. It has no smell to it other > than stinky exhaust, so I don't really know what this is. My coolant > level has not changed noticeably, so I wouldn't think it to be a water > leak, but I can't say with certainty. > > Here are the basics: > 1972 Jeep CJ5 > AMC 304 > Aftermarket parts: > Edlebrock peformer intake > Holley 600cfm 4-bbl carb > Edlebrock shorty headers > > Thanks for any help you guys can give on this. I'm at a loss & don't > know what to do next. > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
On Sun, 15 Jul 2007 11:42:53 -0700, matthew.nye@gmail.com wrote:
>The initial timing is 6 degrees BTDC & the dwell angle is about 31. I >get about 16hg of steady vacuum at idle & about 7psi of fuel pressure >at idle. The idle & even light acceleration is perfect, which makes >me think it's not a timing chain issue, but I don't know enough about >what the symptoms of a slipped chain would be to make that call. When >the engine is at TDC of piston 1's compression stroke, the rotor lines >up perfectly with cylinder 1's plug wire, which also makes me thing >it's not necessarily a timing chain issue. Since I have changed the >plugs & tried to further diagnose the problem, my plugs have turned >black. This along with the popping in the exhaust obviously mean my >mixture is either too rich, or something is going haywire with the >timing & causing the fuel to not burn at higher RPM. One thing worth >noting, is that I have not changed the plugs since they have been >fouled since I replaced the faulty vacuum advance. I didn't know if >this would make a difference or not & didn't want to risk fouling a >new set while troubleshooting. I can literally get flames to shoot >out of my exhaust if I abuse it enough. This happens on both sides & >I have dual exhaust, leading me to think it's not a valve issue, >unless I'm really unlucky & have a problem on both sides of the >engine. > >The jeep is a recreational vehicle of sorts, used primarily to climb >up & down sand dunes. The symptoms all occured when my fuel pump died >about 2 years ago. After I replaced the pump, the engine started >doing this. I've since replaced it again to rule that out with no >change. I've also rebuilt the carburetor, but it was the first time I >ever did such a thing, so it's quite possible I missed something. The >accelerator pump works fine, the idle mixture screws are set very lean >(since I think the mixture is too rich for some reason), the power >valve has been replaced & I even checked it again last week & I can >see spray coming out of the booster venturi when I rev the engine (it >does this whether I'm moving or not). Another thing I noticed is that >when the engine is cold, if I hold my hand in front of the exhaust, it >sprays black fluid on me at idle. It's not a lot, but I noticed it >when it was sprayed on my leg one day. It has no smell to it other >than stinky exhaust, so I don't really know what this is. My coolant >level has not changed noticeably, so I wouldn't think it to be a water >leak, but I can't say with certainty. A few things here. First 16 inch of vacum at a idle is LOW for a 304 with 6 BTDC timing. I have a old 79 J20 with a 360 that I have owned for 22 years now and it pulls about 20 inches at a idle or a bit more. Have you done a health check as far as a compression check and is vacum steady at a idle too? Another thing, as another poster said, a 600 is really too much carb for a 304 and it may be loading up over rich when you get going. You really want someting around a 450 is so tops and it would give you better responce and toruq throught usuable RPM range too. There is some mis conceptions on carbs here, bigger is not always better. The shorty headers are not a good match at all for that engine and its stock cam and might not be helping things either. You might try using a smaller power valve and one that come in later too with current carb say around 4 or 5 inches or maybe size main jets a few sizes smaller. My gut feeling is that it is going over rich and loading up when casrb starts to draw some. The reason it appeared after old pump failed is because it was likely weak on pressure side before failure which would have lowered fuel level in bowl some and in effect leaned it out. You could also install a external pressure regualtor and set it to 4.5 to 5 PSI as 7 PSI is a lot for a carb. You could also try lower fuel level in bowl about 1/4 iches and see if that help before you rejet because that will lean mixtures out. You need to focus on fuel issues here as the plugs are the sign post here, not the cause. One more question, what heat range plug are you running? with headers you usually need to go a bit hotter than stock. ----------------- TheSnoMan.com |
Re: CJ5 misfires at high RPM/hard acceleration
On Sun, 15 Jul 2007 11:42:53 -0700, matthew.nye@gmail.com wrote:
>The initial timing is 6 degrees BTDC & the dwell angle is about 31. I >get about 16hg of steady vacuum at idle & about 7psi of fuel pressure >at idle. The idle & even light acceleration is perfect, which makes >me think it's not a timing chain issue, but I don't know enough about >what the symptoms of a slipped chain would be to make that call. When >the engine is at TDC of piston 1's compression stroke, the rotor lines >up perfectly with cylinder 1's plug wire, which also makes me thing >it's not necessarily a timing chain issue. Since I have changed the >plugs & tried to further diagnose the problem, my plugs have turned >black. This along with the popping in the exhaust obviously mean my >mixture is either too rich, or something is going haywire with the >timing & causing the fuel to not burn at higher RPM. One thing worth >noting, is that I have not changed the plugs since they have been >fouled since I replaced the faulty vacuum advance. I didn't know if >this would make a difference or not & didn't want to risk fouling a >new set while troubleshooting. I can literally get flames to shoot >out of my exhaust if I abuse it enough. This happens on both sides & >I have dual exhaust, leading me to think it's not a valve issue, >unless I'm really unlucky & have a problem on both sides of the >engine. > >The jeep is a recreational vehicle of sorts, used primarily to climb >up & down sand dunes. The symptoms all occured when my fuel pump died >about 2 years ago. After I replaced the pump, the engine started >doing this. I've since replaced it again to rule that out with no >change. I've also rebuilt the carburetor, but it was the first time I >ever did such a thing, so it's quite possible I missed something. The >accelerator pump works fine, the idle mixture screws are set very lean >(since I think the mixture is too rich for some reason), the power >valve has been replaced & I even checked it again last week & I can >see spray coming out of the booster venturi when I rev the engine (it >does this whether I'm moving or not). Another thing I noticed is that >when the engine is cold, if I hold my hand in front of the exhaust, it >sprays black fluid on me at idle. It's not a lot, but I noticed it >when it was sprayed on my leg one day. It has no smell to it other >than stinky exhaust, so I don't really know what this is. My coolant >level has not changed noticeably, so I wouldn't think it to be a water >leak, but I can't say with certainty. A few things here. First 16 inch of vacum at a idle is LOW for a 304 with 6 BTDC timing. I have a old 79 J20 with a 360 that I have owned for 22 years now and it pulls about 20 inches at a idle or a bit more. Have you done a health check as far as a compression check and is vacum steady at a idle too? Another thing, as another poster said, a 600 is really too much carb for a 304 and it may be loading up over rich when you get going. You really want someting around a 450 is so tops and it would give you better responce and toruq throught usuable RPM range too. There is some mis conceptions on carbs here, bigger is not always better. The shorty headers are not a good match at all for that engine and its stock cam and might not be helping things either. You might try using a smaller power valve and one that come in later too with current carb say around 4 or 5 inches or maybe size main jets a few sizes smaller. My gut feeling is that it is going over rich and loading up when casrb starts to draw some. The reason it appeared after old pump failed is because it was likely weak on pressure side before failure which would have lowered fuel level in bowl some and in effect leaned it out. You could also install a external pressure regualtor and set it to 4.5 to 5 PSI as 7 PSI is a lot for a carb. You could also try lower fuel level in bowl about 1/4 iches and see if that help before you rejet because that will lean mixtures out. You need to focus on fuel issues here as the plugs are the sign post here, not the cause. One more question, what heat range plug are you running? with headers you usually need to go a bit hotter than stock. ----------------- TheSnoMan.com |
Re: CJ5 misfires at high RPM/hard acceleration
On Sun, 15 Jul 2007 11:42:53 -0700, matthew.nye@gmail.com wrote:
>The initial timing is 6 degrees BTDC & the dwell angle is about 31. I >get about 16hg of steady vacuum at idle & about 7psi of fuel pressure >at idle. The idle & even light acceleration is perfect, which makes >me think it's not a timing chain issue, but I don't know enough about >what the symptoms of a slipped chain would be to make that call. When >the engine is at TDC of piston 1's compression stroke, the rotor lines >up perfectly with cylinder 1's plug wire, which also makes me thing >it's not necessarily a timing chain issue. Since I have changed the >plugs & tried to further diagnose the problem, my plugs have turned >black. This along with the popping in the exhaust obviously mean my >mixture is either too rich, or something is going haywire with the >timing & causing the fuel to not burn at higher RPM. One thing worth >noting, is that I have not changed the plugs since they have been >fouled since I replaced the faulty vacuum advance. I didn't know if >this would make a difference or not & didn't want to risk fouling a >new set while troubleshooting. I can literally get flames to shoot >out of my exhaust if I abuse it enough. This happens on both sides & >I have dual exhaust, leading me to think it's not a valve issue, >unless I'm really unlucky & have a problem on both sides of the >engine. > >The jeep is a recreational vehicle of sorts, used primarily to climb >up & down sand dunes. The symptoms all occured when my fuel pump died >about 2 years ago. After I replaced the pump, the engine started >doing this. I've since replaced it again to rule that out with no >change. I've also rebuilt the carburetor, but it was the first time I >ever did such a thing, so it's quite possible I missed something. The >accelerator pump works fine, the idle mixture screws are set very lean >(since I think the mixture is too rich for some reason), the power >valve has been replaced & I even checked it again last week & I can >see spray coming out of the booster venturi when I rev the engine (it >does this whether I'm moving or not). Another thing I noticed is that >when the engine is cold, if I hold my hand in front of the exhaust, it >sprays black fluid on me at idle. It's not a lot, but I noticed it >when it was sprayed on my leg one day. It has no smell to it other >than stinky exhaust, so I don't really know what this is. My coolant >level has not changed noticeably, so I wouldn't think it to be a water >leak, but I can't say with certainty. A few things here. First 16 inch of vacum at a idle is LOW for a 304 with 6 BTDC timing. I have a old 79 J20 with a 360 that I have owned for 22 years now and it pulls about 20 inches at a idle or a bit more. Have you done a health check as far as a compression check and is vacum steady at a idle too? Another thing, as another poster said, a 600 is really too much carb for a 304 and it may be loading up over rich when you get going. You really want someting around a 450 is so tops and it would give you better responce and toruq throught usuable RPM range too. There is some mis conceptions on carbs here, bigger is not always better. The shorty headers are not a good match at all for that engine and its stock cam and might not be helping things either. You might try using a smaller power valve and one that come in later too with current carb say around 4 or 5 inches or maybe size main jets a few sizes smaller. My gut feeling is that it is going over rich and loading up when casrb starts to draw some. The reason it appeared after old pump failed is because it was likely weak on pressure side before failure which would have lowered fuel level in bowl some and in effect leaned it out. You could also install a external pressure regualtor and set it to 4.5 to 5 PSI as 7 PSI is a lot for a carb. You could also try lower fuel level in bowl about 1/4 iches and see if that help before you rejet because that will lean mixtures out. You need to focus on fuel issues here as the plugs are the sign post here, not the cause. One more question, what heat range plug are you running? with headers you usually need to go a bit hotter than stock. ----------------- TheSnoMan.com |
Re: CJ5 misfires at high RPM/hard acceleration
On Sun, 15 Jul 2007 11:42:53 -0700, matthew.nye@gmail.com wrote:
>The initial timing is 6 degrees BTDC & the dwell angle is about 31. I >get about 16hg of steady vacuum at idle & about 7psi of fuel pressure >at idle. The idle & even light acceleration is perfect, which makes >me think it's not a timing chain issue, but I don't know enough about >what the symptoms of a slipped chain would be to make that call. When >the engine is at TDC of piston 1's compression stroke, the rotor lines >up perfectly with cylinder 1's plug wire, which also makes me thing >it's not necessarily a timing chain issue. Since I have changed the >plugs & tried to further diagnose the problem, my plugs have turned >black. This along with the popping in the exhaust obviously mean my >mixture is either too rich, or something is going haywire with the >timing & causing the fuel to not burn at higher RPM. One thing worth >noting, is that I have not changed the plugs since they have been >fouled since I replaced the faulty vacuum advance. I didn't know if >this would make a difference or not & didn't want to risk fouling a >new set while troubleshooting. I can literally get flames to shoot >out of my exhaust if I abuse it enough. This happens on both sides & >I have dual exhaust, leading me to think it's not a valve issue, >unless I'm really unlucky & have a problem on both sides of the >engine. > >The jeep is a recreational vehicle of sorts, used primarily to climb >up & down sand dunes. The symptoms all occured when my fuel pump died >about 2 years ago. After I replaced the pump, the engine started >doing this. I've since replaced it again to rule that out with no >change. I've also rebuilt the carburetor, but it was the first time I >ever did such a thing, so it's quite possible I missed something. The >accelerator pump works fine, the idle mixture screws are set very lean >(since I think the mixture is too rich for some reason), the power >valve has been replaced & I even checked it again last week & I can >see spray coming out of the booster venturi when I rev the engine (it >does this whether I'm moving or not). Another thing I noticed is that >when the engine is cold, if I hold my hand in front of the exhaust, it >sprays black fluid on me at idle. It's not a lot, but I noticed it >when it was sprayed on my leg one day. It has no smell to it other >than stinky exhaust, so I don't really know what this is. My coolant >level has not changed noticeably, so I wouldn't think it to be a water >leak, but I can't say with certainty. A few things here. First 16 inch of vacum at a idle is LOW for a 304 with 6 BTDC timing. I have a old 79 J20 with a 360 that I have owned for 22 years now and it pulls about 20 inches at a idle or a bit more. Have you done a health check as far as a compression check and is vacum steady at a idle too? Another thing, as another poster said, a 600 is really too much carb for a 304 and it may be loading up over rich when you get going. You really want someting around a 450 is so tops and it would give you better responce and toruq throught usuable RPM range too. There is some mis conceptions on carbs here, bigger is not always better. The shorty headers are not a good match at all for that engine and its stock cam and might not be helping things either. You might try using a smaller power valve and one that come in later too with current carb say around 4 or 5 inches or maybe size main jets a few sizes smaller. My gut feeling is that it is going over rich and loading up when casrb starts to draw some. The reason it appeared after old pump failed is because it was likely weak on pressure side before failure which would have lowered fuel level in bowl some and in effect leaned it out. You could also install a external pressure regualtor and set it to 4.5 to 5 PSI as 7 PSI is a lot for a carb. You could also try lower fuel level in bowl about 1/4 iches and see if that help before you rejet because that will lean mixtures out. You need to focus on fuel issues here as the plugs are the sign post here, not the cause. One more question, what heat range plug are you running? with headers you usually need to go a bit hotter than stock. ----------------- TheSnoMan.com |
Re: CJ5 misfires at high RPM/hard acceleration
Thanks for everyone's replies. Here's what I've done from your
suggestions: - Having the gas cap off made no difference. I actually don't have any of the emissions stuff on it, so there's no canister, just the gas tank to the pump. - Having the coil's + lead hooked directly to the battery made no difference, I tried switching the leads on the ballast resistor too first to see if I had it hooked up wrong. I may be wrong, but I think the ballast resistor leads can go either way? - I tried what Roy suggested with interesting results. When I advanced the engine to 10 or 15 degrees, it would run noticeably better, but not perfect. I could actually get the secondaries to open up on the carb before it crapped out, which I haven't been able to do since the fuel pump change. I was grabbing at straws when I replaced the vacuum advance. I could suck air right through it with my mouth so I knew it was bad, that & having it plugged in at idle made no difference in timing advance. When I have the new one plugged in, it automatically advances it to about 10 BTDC at idle. I didn't see any adjustments on it, but maybe that's what is wrong? I couldn't get the engine started with it advanced so far when testing, I could only test it out by having it started first & then advancing it. The idle was terrible with a lot of misfiring at that point, if that means anything. - I've had a few people also tell me it's over carbureted, but that's what has always been on it (my dad owned it for like about 15 years before me) & it seemed to have ran fine for the longest time. That is an interesting theory though that the old pump could have just been so tired that it didn't put enough pressure through to put it at it's full potential. I was considering a 500cfm 2-bbl holley if I had to purchase one, but it sounds like that might be too much as well? To clarify, the pump just started leaking when it went out, it didn't seize up or anything, in fact I didn't know it was going bad until I started getting sprayed with gas (there's no fenders, windshield, etc). I don't know if I cleaned the jets out good enough when I rebuilt the carb, so it's a possibility that part of the diaphragm got stuck in it. it does seem to flow OK though when I look at the spray coming out of the jets. - The vacuum is very steady at idle, maybe 1hg of movement at most from side to side. I have not performed a compression check, what would that tell me if it were low? I don't have a compression tester available so I'm not going to be able to do that one right away. - The plugs are bosch platinums with a heat rating of 9. I'm not sure what that equates to heat-wise though, is that a standard across all plugs?\ Any suggestions on the distributor? I checked the springs & weights of the centrifugal advance & they seem to be nice & responsive, but then again, I'm not sure what they're supposed to look like. Should I try replacing the entire distributor before I go crazy & take the entire front of my engine apart for the timing chain or start messing with the carb? Is there any way to test whether or not the timing chain has slipped a tooth without actually looking at it? Thanks again guys, -Matt |
Re: CJ5 misfires at high RPM/hard acceleration
Thanks for everyone's replies. Here's what I've done from your
suggestions: - Having the gas cap off made no difference. I actually don't have any of the emissions stuff on it, so there's no canister, just the gas tank to the pump. - Having the coil's + lead hooked directly to the battery made no difference, I tried switching the leads on the ballast resistor too first to see if I had it hooked up wrong. I may be wrong, but I think the ballast resistor leads can go either way? - I tried what Roy suggested with interesting results. When I advanced the engine to 10 or 15 degrees, it would run noticeably better, but not perfect. I could actually get the secondaries to open up on the carb before it crapped out, which I haven't been able to do since the fuel pump change. I was grabbing at straws when I replaced the vacuum advance. I could suck air right through it with my mouth so I knew it was bad, that & having it plugged in at idle made no difference in timing advance. When I have the new one plugged in, it automatically advances it to about 10 BTDC at idle. I didn't see any adjustments on it, but maybe that's what is wrong? I couldn't get the engine started with it advanced so far when testing, I could only test it out by having it started first & then advancing it. The idle was terrible with a lot of misfiring at that point, if that means anything. - I've had a few people also tell me it's over carbureted, but that's what has always been on it (my dad owned it for like about 15 years before me) & it seemed to have ran fine for the longest time. That is an interesting theory though that the old pump could have just been so tired that it didn't put enough pressure through to put it at it's full potential. I was considering a 500cfm 2-bbl holley if I had to purchase one, but it sounds like that might be too much as well? To clarify, the pump just started leaking when it went out, it didn't seize up or anything, in fact I didn't know it was going bad until I started getting sprayed with gas (there's no fenders, windshield, etc). I don't know if I cleaned the jets out good enough when I rebuilt the carb, so it's a possibility that part of the diaphragm got stuck in it. it does seem to flow OK though when I look at the spray coming out of the jets. - The vacuum is very steady at idle, maybe 1hg of movement at most from side to side. I have not performed a compression check, what would that tell me if it were low? I don't have a compression tester available so I'm not going to be able to do that one right away. - The plugs are bosch platinums with a heat rating of 9. I'm not sure what that equates to heat-wise though, is that a standard across all plugs?\ Any suggestions on the distributor? I checked the springs & weights of the centrifugal advance & they seem to be nice & responsive, but then again, I'm not sure what they're supposed to look like. Should I try replacing the entire distributor before I go crazy & take the entire front of my engine apart for the timing chain or start messing with the carb? Is there any way to test whether or not the timing chain has slipped a tooth without actually looking at it? Thanks again guys, -Matt |
Re: CJ5 misfires at high RPM/hard acceleration
Thanks for everyone's replies. Here's what I've done from your
suggestions: - Having the gas cap off made no difference. I actually don't have any of the emissions stuff on it, so there's no canister, just the gas tank to the pump. - Having the coil's + lead hooked directly to the battery made no difference, I tried switching the leads on the ballast resistor too first to see if I had it hooked up wrong. I may be wrong, but I think the ballast resistor leads can go either way? - I tried what Roy suggested with interesting results. When I advanced the engine to 10 or 15 degrees, it would run noticeably better, but not perfect. I could actually get the secondaries to open up on the carb before it crapped out, which I haven't been able to do since the fuel pump change. I was grabbing at straws when I replaced the vacuum advance. I could suck air right through it with my mouth so I knew it was bad, that & having it plugged in at idle made no difference in timing advance. When I have the new one plugged in, it automatically advances it to about 10 BTDC at idle. I didn't see any adjustments on it, but maybe that's what is wrong? I couldn't get the engine started with it advanced so far when testing, I could only test it out by having it started first & then advancing it. The idle was terrible with a lot of misfiring at that point, if that means anything. - I've had a few people also tell me it's over carbureted, but that's what has always been on it (my dad owned it for like about 15 years before me) & it seemed to have ran fine for the longest time. That is an interesting theory though that the old pump could have just been so tired that it didn't put enough pressure through to put it at it's full potential. I was considering a 500cfm 2-bbl holley if I had to purchase one, but it sounds like that might be too much as well? To clarify, the pump just started leaking when it went out, it didn't seize up or anything, in fact I didn't know it was going bad until I started getting sprayed with gas (there's no fenders, windshield, etc). I don't know if I cleaned the jets out good enough when I rebuilt the carb, so it's a possibility that part of the diaphragm got stuck in it. it does seem to flow OK though when I look at the spray coming out of the jets. - The vacuum is very steady at idle, maybe 1hg of movement at most from side to side. I have not performed a compression check, what would that tell me if it were low? I don't have a compression tester available so I'm not going to be able to do that one right away. - The plugs are bosch platinums with a heat rating of 9. I'm not sure what that equates to heat-wise though, is that a standard across all plugs?\ Any suggestions on the distributor? I checked the springs & weights of the centrifugal advance & they seem to be nice & responsive, but then again, I'm not sure what they're supposed to look like. Should I try replacing the entire distributor before I go crazy & take the entire front of my engine apart for the timing chain or start messing with the carb? Is there any way to test whether or not the timing chain has slipped a tooth without actually looking at it? Thanks again guys, -Matt |
Re: CJ5 misfires at high RPM/hard acceleration
Thanks for everyone's replies. Here's what I've done from your
suggestions: - Having the gas cap off made no difference. I actually don't have any of the emissions stuff on it, so there's no canister, just the gas tank to the pump. - Having the coil's + lead hooked directly to the battery made no difference, I tried switching the leads on the ballast resistor too first to see if I had it hooked up wrong. I may be wrong, but I think the ballast resistor leads can go either way? - I tried what Roy suggested with interesting results. When I advanced the engine to 10 or 15 degrees, it would run noticeably better, but not perfect. I could actually get the secondaries to open up on the carb before it crapped out, which I haven't been able to do since the fuel pump change. I was grabbing at straws when I replaced the vacuum advance. I could suck air right through it with my mouth so I knew it was bad, that & having it plugged in at idle made no difference in timing advance. When I have the new one plugged in, it automatically advances it to about 10 BTDC at idle. I didn't see any adjustments on it, but maybe that's what is wrong? I couldn't get the engine started with it advanced so far when testing, I could only test it out by having it started first & then advancing it. The idle was terrible with a lot of misfiring at that point, if that means anything. - I've had a few people also tell me it's over carbureted, but that's what has always been on it (my dad owned it for like about 15 years before me) & it seemed to have ran fine for the longest time. That is an interesting theory though that the old pump could have just been so tired that it didn't put enough pressure through to put it at it's full potential. I was considering a 500cfm 2-bbl holley if I had to purchase one, but it sounds like that might be too much as well? To clarify, the pump just started leaking when it went out, it didn't seize up or anything, in fact I didn't know it was going bad until I started getting sprayed with gas (there's no fenders, windshield, etc). I don't know if I cleaned the jets out good enough when I rebuilt the carb, so it's a possibility that part of the diaphragm got stuck in it. it does seem to flow OK though when I look at the spray coming out of the jets. - The vacuum is very steady at idle, maybe 1hg of movement at most from side to side. I have not performed a compression check, what would that tell me if it were low? I don't have a compression tester available so I'm not going to be able to do that one right away. - The plugs are bosch platinums with a heat rating of 9. I'm not sure what that equates to heat-wise though, is that a standard across all plugs?\ Any suggestions on the distributor? I checked the springs & weights of the centrifugal advance & they seem to be nice & responsive, but then again, I'm not sure what they're supposed to look like. Should I try replacing the entire distributor before I go crazy & take the entire front of my engine apart for the timing chain or start messing with the carb? Is there any way to test whether or not the timing chain has slipped a tooth without actually looking at it? Thanks again guys, -Matt |
Re: CJ5 misfires at high RPM/hard acceleration
I'm a small block chevy fan with no hands on with the 304, but...........
I'm betting on a screwed up distributor. Several thoughts: The vacumn advance works a bit counterintuitive: at full (high) manifold vacumn (idle or down hill cruising) the distributor advances your base setting around 15 degrees. I I read your post correctly you are seeing it advance from 6 degrees to 10 degrees when you plug in the advance vac line. Not anywhere near enough. Test: let it idle, get out the timing light, plug/unplug the vac line to the distributor. You should see about 15 degree jump. If not, pull the distributor cap and rotor, check to see that the the advance plate moves nicely when you really suck on it The centrifical advance (weights and springs) puts in another 20 degrees or so, no advance at idle, full advance at 2500 to 3000 rpm (small block numbers here) Test by plugging the vac advance line, reving the engine as high as it will go (it usually stuggles to get to 3000 rpm), make sure you see the 20 degree advance come in with speed increase. It doesn't jump like the vac advance test. If not, make sure the springs and cam move easily. The combination of these gives you advance numbers like this: Set basic advance to 6 BTDC with vac advance disconnneted Connect vac advance, should hop to 20 to 25 BTDC Rev slowly to 3000, no load, should go to 35-40 BTDC. Rev quickly or heavy load, to 3000, 6 + 20 or 26 BTDC. I'd consider the 31 degrees of dwell to be pretty skimpy for a V-8, I'd be setting it at 38 to 40. This changes your timing so you have to redo that. matthew.nye@gmail.com wrote: > Thanks for everyone's replies. Here's what I've done from your > suggestions: > > - Having the gas cap off made no difference. I actually don't have > any of the emissions stuff on it, so there's no canister, just the gas > tank to the pump. > - Having the coil's + lead hooked directly to the battery made no > difference, I tried switching the leads on the ballast resistor too > first to see if I had it hooked up wrong. I may be wrong, but I think > the ballast resistor leads can go either way? > - I tried what Roy suggested with interesting results. When I > advanced the engine to 10 or 15 degrees, it would run noticeably > better, but not perfect. I could actually get the secondaries to open > up on the carb before it crapped out, which I haven't been able to do > since the fuel pump change. I was grabbing at straws when I replaced > the vacuum advance. I could suck air right through it with my mouth > so I knew it was bad, that & having it plugged in at idle made no > difference in timing advance. When I have the new one plugged in, it > automatically advances it to about 10 BTDC at idle. I didn't see any > adjustments on it, but maybe that's what is wrong? I couldn't get the > engine started with it advanced so far when testing, I could only test > it out by having it started first & then advancing it. The idle was > terrible with a lot of misfiring at that point, if that means > anything. > - I've had a few people also tell me it's over carbureted, but that's > what has always been on it (my dad owned it for like about 15 years > before me) & it seemed to have ran fine for the longest time. That is > an interesting theory though that the old pump could have just been so > tired that it didn't put enough pressure through to put it at it's > full potential. I was considering a 500cfm 2-bbl holley if I had to > purchase one, but it sounds like that might be too much as well? To > clarify, the pump just started leaking when it went out, it didn't > seize up or anything, in fact I didn't know it was going bad until I > started getting sprayed with gas (there's no fenders, windshield, > etc). I don't know if I cleaned the jets out good enough when I > rebuilt the carb, so it's a possibility that part of the diaphragm got > stuck in it. it does seem to flow OK though when I look at the spray > coming out of the jets. > - The vacuum is very steady at idle, maybe 1hg of movement at most > from side to side. I have not performed a compression check, what > would that tell me if it were low? I don't have a compression tester > available so I'm not going to be able to do that one right away. > - The plugs are bosch platinums with a heat rating of 9. I'm not sure > what that equates to heat-wise though, is that a standard across all > plugs?\ > > Any suggestions on the distributor? I checked the springs & weights > of the centrifugal advance & they seem to be nice & responsive, but > then again, I'm not sure what they're supposed to look like. Should I > try replacing the entire distributor before I go crazy & take the > entire front of my engine apart for the timing chain or start messing > with the carb? Is there any way to test whether or not the timing > chain has slipped a tooth without actually looking at it? > > Thanks again guys, > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
I'm a small block chevy fan with no hands on with the 304, but...........
I'm betting on a screwed up distributor. Several thoughts: The vacumn advance works a bit counterintuitive: at full (high) manifold vacumn (idle or down hill cruising) the distributor advances your base setting around 15 degrees. I I read your post correctly you are seeing it advance from 6 degrees to 10 degrees when you plug in the advance vac line. Not anywhere near enough. Test: let it idle, get out the timing light, plug/unplug the vac line to the distributor. You should see about 15 degree jump. If not, pull the distributor cap and rotor, check to see that the the advance plate moves nicely when you really suck on it The centrifical advance (weights and springs) puts in another 20 degrees or so, no advance at idle, full advance at 2500 to 3000 rpm (small block numbers here) Test by plugging the vac advance line, reving the engine as high as it will go (it usually stuggles to get to 3000 rpm), make sure you see the 20 degree advance come in with speed increase. It doesn't jump like the vac advance test. If not, make sure the springs and cam move easily. The combination of these gives you advance numbers like this: Set basic advance to 6 BTDC with vac advance disconnneted Connect vac advance, should hop to 20 to 25 BTDC Rev slowly to 3000, no load, should go to 35-40 BTDC. Rev quickly or heavy load, to 3000, 6 + 20 or 26 BTDC. I'd consider the 31 degrees of dwell to be pretty skimpy for a V-8, I'd be setting it at 38 to 40. This changes your timing so you have to redo that. matthew.nye@gmail.com wrote: > Thanks for everyone's replies. Here's what I've done from your > suggestions: > > - Having the gas cap off made no difference. I actually don't have > any of the emissions stuff on it, so there's no canister, just the gas > tank to the pump. > - Having the coil's + lead hooked directly to the battery made no > difference, I tried switching the leads on the ballast resistor too > first to see if I had it hooked up wrong. I may be wrong, but I think > the ballast resistor leads can go either way? > - I tried what Roy suggested with interesting results. When I > advanced the engine to 10 or 15 degrees, it would run noticeably > better, but not perfect. I could actually get the secondaries to open > up on the carb before it crapped out, which I haven't been able to do > since the fuel pump change. I was grabbing at straws when I replaced > the vacuum advance. I could suck air right through it with my mouth > so I knew it was bad, that & having it plugged in at idle made no > difference in timing advance. When I have the new one plugged in, it > automatically advances it to about 10 BTDC at idle. I didn't see any > adjustments on it, but maybe that's what is wrong? I couldn't get the > engine started with it advanced so far when testing, I could only test > it out by having it started first & then advancing it. The idle was > terrible with a lot of misfiring at that point, if that means > anything. > - I've had a few people also tell me it's over carbureted, but that's > what has always been on it (my dad owned it for like about 15 years > before me) & it seemed to have ran fine for the longest time. That is > an interesting theory though that the old pump could have just been so > tired that it didn't put enough pressure through to put it at it's > full potential. I was considering a 500cfm 2-bbl holley if I had to > purchase one, but it sounds like that might be too much as well? To > clarify, the pump just started leaking when it went out, it didn't > seize up or anything, in fact I didn't know it was going bad until I > started getting sprayed with gas (there's no fenders, windshield, > etc). I don't know if I cleaned the jets out good enough when I > rebuilt the carb, so it's a possibility that part of the diaphragm got > stuck in it. it does seem to flow OK though when I look at the spray > coming out of the jets. > - The vacuum is very steady at idle, maybe 1hg of movement at most > from side to side. I have not performed a compression check, what > would that tell me if it were low? I don't have a compression tester > available so I'm not going to be able to do that one right away. > - The plugs are bosch platinums with a heat rating of 9. I'm not sure > what that equates to heat-wise though, is that a standard across all > plugs?\ > > Any suggestions on the distributor? I checked the springs & weights > of the centrifugal advance & they seem to be nice & responsive, but > then again, I'm not sure what they're supposed to look like. Should I > try replacing the entire distributor before I go crazy & take the > entire front of my engine apart for the timing chain or start messing > with the carb? Is there any way to test whether or not the timing > chain has slipped a tooth without actually looking at it? > > Thanks again guys, > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
I'm a small block chevy fan with no hands on with the 304, but...........
I'm betting on a screwed up distributor. Several thoughts: The vacumn advance works a bit counterintuitive: at full (high) manifold vacumn (idle or down hill cruising) the distributor advances your base setting around 15 degrees. I I read your post correctly you are seeing it advance from 6 degrees to 10 degrees when you plug in the advance vac line. Not anywhere near enough. Test: let it idle, get out the timing light, plug/unplug the vac line to the distributor. You should see about 15 degree jump. If not, pull the distributor cap and rotor, check to see that the the advance plate moves nicely when you really suck on it The centrifical advance (weights and springs) puts in another 20 degrees or so, no advance at idle, full advance at 2500 to 3000 rpm (small block numbers here) Test by plugging the vac advance line, reving the engine as high as it will go (it usually stuggles to get to 3000 rpm), make sure you see the 20 degree advance come in with speed increase. It doesn't jump like the vac advance test. If not, make sure the springs and cam move easily. The combination of these gives you advance numbers like this: Set basic advance to 6 BTDC with vac advance disconnneted Connect vac advance, should hop to 20 to 25 BTDC Rev slowly to 3000, no load, should go to 35-40 BTDC. Rev quickly or heavy load, to 3000, 6 + 20 or 26 BTDC. I'd consider the 31 degrees of dwell to be pretty skimpy for a V-8, I'd be setting it at 38 to 40. This changes your timing so you have to redo that. matthew.nye@gmail.com wrote: > Thanks for everyone's replies. Here's what I've done from your > suggestions: > > - Having the gas cap off made no difference. I actually don't have > any of the emissions stuff on it, so there's no canister, just the gas > tank to the pump. > - Having the coil's + lead hooked directly to the battery made no > difference, I tried switching the leads on the ballast resistor too > first to see if I had it hooked up wrong. I may be wrong, but I think > the ballast resistor leads can go either way? > - I tried what Roy suggested with interesting results. When I > advanced the engine to 10 or 15 degrees, it would run noticeably > better, but not perfect. I could actually get the secondaries to open > up on the carb before it crapped out, which I haven't been able to do > since the fuel pump change. I was grabbing at straws when I replaced > the vacuum advance. I could suck air right through it with my mouth > so I knew it was bad, that & having it plugged in at idle made no > difference in timing advance. When I have the new one plugged in, it > automatically advances it to about 10 BTDC at idle. I didn't see any > adjustments on it, but maybe that's what is wrong? I couldn't get the > engine started with it advanced so far when testing, I could only test > it out by having it started first & then advancing it. The idle was > terrible with a lot of misfiring at that point, if that means > anything. > - I've had a few people also tell me it's over carbureted, but that's > what has always been on it (my dad owned it for like about 15 years > before me) & it seemed to have ran fine for the longest time. That is > an interesting theory though that the old pump could have just been so > tired that it didn't put enough pressure through to put it at it's > full potential. I was considering a 500cfm 2-bbl holley if I had to > purchase one, but it sounds like that might be too much as well? To > clarify, the pump just started leaking when it went out, it didn't > seize up or anything, in fact I didn't know it was going bad until I > started getting sprayed with gas (there's no fenders, windshield, > etc). I don't know if I cleaned the jets out good enough when I > rebuilt the carb, so it's a possibility that part of the diaphragm got > stuck in it. it does seem to flow OK though when I look at the spray > coming out of the jets. > - The vacuum is very steady at idle, maybe 1hg of movement at most > from side to side. I have not performed a compression check, what > would that tell me if it were low? I don't have a compression tester > available so I'm not going to be able to do that one right away. > - The plugs are bosch platinums with a heat rating of 9. I'm not sure > what that equates to heat-wise though, is that a standard across all > plugs?\ > > Any suggestions on the distributor? I checked the springs & weights > of the centrifugal advance & they seem to be nice & responsive, but > then again, I'm not sure what they're supposed to look like. Should I > try replacing the entire distributor before I go crazy & take the > entire front of my engine apart for the timing chain or start messing > with the carb? Is there any way to test whether or not the timing > chain has slipped a tooth without actually looking at it? > > Thanks again guys, > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
I'm a small block chevy fan with no hands on with the 304, but...........
I'm betting on a screwed up distributor. Several thoughts: The vacumn advance works a bit counterintuitive: at full (high) manifold vacumn (idle or down hill cruising) the distributor advances your base setting around 15 degrees. I I read your post correctly you are seeing it advance from 6 degrees to 10 degrees when you plug in the advance vac line. Not anywhere near enough. Test: let it idle, get out the timing light, plug/unplug the vac line to the distributor. You should see about 15 degree jump. If not, pull the distributor cap and rotor, check to see that the the advance plate moves nicely when you really suck on it The centrifical advance (weights and springs) puts in another 20 degrees or so, no advance at idle, full advance at 2500 to 3000 rpm (small block numbers here) Test by plugging the vac advance line, reving the engine as high as it will go (it usually stuggles to get to 3000 rpm), make sure you see the 20 degree advance come in with speed increase. It doesn't jump like the vac advance test. If not, make sure the springs and cam move easily. The combination of these gives you advance numbers like this: Set basic advance to 6 BTDC with vac advance disconnneted Connect vac advance, should hop to 20 to 25 BTDC Rev slowly to 3000, no load, should go to 35-40 BTDC. Rev quickly or heavy load, to 3000, 6 + 20 or 26 BTDC. I'd consider the 31 degrees of dwell to be pretty skimpy for a V-8, I'd be setting it at 38 to 40. This changes your timing so you have to redo that. matthew.nye@gmail.com wrote: > Thanks for everyone's replies. Here's what I've done from your > suggestions: > > - Having the gas cap off made no difference. I actually don't have > any of the emissions stuff on it, so there's no canister, just the gas > tank to the pump. > - Having the coil's + lead hooked directly to the battery made no > difference, I tried switching the leads on the ballast resistor too > first to see if I had it hooked up wrong. I may be wrong, but I think > the ballast resistor leads can go either way? > - I tried what Roy suggested with interesting results. When I > advanced the engine to 10 or 15 degrees, it would run noticeably > better, but not perfect. I could actually get the secondaries to open > up on the carb before it crapped out, which I haven't been able to do > since the fuel pump change. I was grabbing at straws when I replaced > the vacuum advance. I could suck air right through it with my mouth > so I knew it was bad, that & having it plugged in at idle made no > difference in timing advance. When I have the new one plugged in, it > automatically advances it to about 10 BTDC at idle. I didn't see any > adjustments on it, but maybe that's what is wrong? I couldn't get the > engine started with it advanced so far when testing, I could only test > it out by having it started first & then advancing it. The idle was > terrible with a lot of misfiring at that point, if that means > anything. > - I've had a few people also tell me it's over carbureted, but that's > what has always been on it (my dad owned it for like about 15 years > before me) & it seemed to have ran fine for the longest time. That is > an interesting theory though that the old pump could have just been so > tired that it didn't put enough pressure through to put it at it's > full potential. I was considering a 500cfm 2-bbl holley if I had to > purchase one, but it sounds like that might be too much as well? To > clarify, the pump just started leaking when it went out, it didn't > seize up or anything, in fact I didn't know it was going bad until I > started getting sprayed with gas (there's no fenders, windshield, > etc). I don't know if I cleaned the jets out good enough when I > rebuilt the carb, so it's a possibility that part of the diaphragm got > stuck in it. it does seem to flow OK though when I look at the spray > coming out of the jets. > - The vacuum is very steady at idle, maybe 1hg of movement at most > from side to side. I have not performed a compression check, what > would that tell me if it were low? I don't have a compression tester > available so I'm not going to be able to do that one right away. > - The plugs are bosch platinums with a heat rating of 9. I'm not sure > what that equates to heat-wise though, is that a standard across all > plugs?\ > > Any suggestions on the distributor? I checked the springs & weights > of the centrifugal advance & they seem to be nice & responsive, but > then again, I'm not sure what they're supposed to look like. Should I > try replacing the entire distributor before I go crazy & take the > entire front of my engine apart for the timing chain or start messing > with the carb? Is there any way to test whether or not the timing > chain has slipped a tooth without actually looking at it? > > Thanks again guys, > > -Matt > |
Re: CJ5 misfires at high RPM/hard acceleration
In article <1184542280.091378.265490@o61g2000hsh.googlegroups .com>,
<matthew.nye@gmail.com> wrote: > Thanks for everyone's replies. Here's what I've done from your > suggestions: Yes the ballast resistor can go either way. The gas you see squirting out when you move the linkage has nothing to do with the secondaries working or not. Although the 600 is "in theory" a little large for a stock 304, if it's tuned right there is no problem. I have a Holley 600 on a 289 that runs perfectly. I agree that your total timing is on the conservative side, but I don't think it would cause your particular symptoms. I had a 390 in a station wagon that would eventually get up to 70mph, but only at light enough throttle where the vacuum stayed high. When I started to put my foot down, it would actually *decelerate*. Nothing I did with the distributor changed that. (I bought it in this condition, so I had no frame of reference). The previous owner had the timing apparently set right. But, just because the distributor is firing with the crank doesn't mean the cam is in the right place. Of course, it turned out to be the chain. |
Re: CJ5 misfires at high RPM/hard acceleration
In article <1184542280.091378.265490@o61g2000hsh.googlegroups .com>,
<matthew.nye@gmail.com> wrote: > Thanks for everyone's replies. Here's what I've done from your > suggestions: Yes the ballast resistor can go either way. The gas you see squirting out when you move the linkage has nothing to do with the secondaries working or not. Although the 600 is "in theory" a little large for a stock 304, if it's tuned right there is no problem. I have a Holley 600 on a 289 that runs perfectly. I agree that your total timing is on the conservative side, but I don't think it would cause your particular symptoms. I had a 390 in a station wagon that would eventually get up to 70mph, but only at light enough throttle where the vacuum stayed high. When I started to put my foot down, it would actually *decelerate*. Nothing I did with the distributor changed that. (I bought it in this condition, so I had no frame of reference). The previous owner had the timing apparently set right. But, just because the distributor is firing with the crank doesn't mean the cam is in the right place. Of course, it turned out to be the chain. |
Re: CJ5 misfires at high RPM/hard acceleration
In article <1184542280.091378.265490@o61g2000hsh.googlegroups .com>,
<matthew.nye@gmail.com> wrote: > Thanks for everyone's replies. Here's what I've done from your > suggestions: Yes the ballast resistor can go either way. The gas you see squirting out when you move the linkage has nothing to do with the secondaries working or not. Although the 600 is "in theory" a little large for a stock 304, if it's tuned right there is no problem. I have a Holley 600 on a 289 that runs perfectly. I agree that your total timing is on the conservative side, but I don't think it would cause your particular symptoms. I had a 390 in a station wagon that would eventually get up to 70mph, but only at light enough throttle where the vacuum stayed high. When I started to put my foot down, it would actually *decelerate*. Nothing I did with the distributor changed that. (I bought it in this condition, so I had no frame of reference). The previous owner had the timing apparently set right. But, just because the distributor is firing with the crank doesn't mean the cam is in the right place. Of course, it turned out to be the chain. |
Re: CJ5 misfires at high RPM/hard acceleration
In article <1184542280.091378.265490@o61g2000hsh.googlegroups .com>,
<matthew.nye@gmail.com> wrote: > Thanks for everyone's replies. Here's what I've done from your > suggestions: Yes the ballast resistor can go either way. The gas you see squirting out when you move the linkage has nothing to do with the secondaries working or not. Although the 600 is "in theory" a little large for a stock 304, if it's tuned right there is no problem. I have a Holley 600 on a 289 that runs perfectly. I agree that your total timing is on the conservative side, but I don't think it would cause your particular symptoms. I had a 390 in a station wagon that would eventually get up to 70mph, but only at light enough throttle where the vacuum stayed high. When I started to put my foot down, it would actually *decelerate*. Nothing I did with the distributor changed that. (I bought it in this condition, so I had no frame of reference). The previous owner had the timing apparently set right. But, just because the distributor is firing with the crank doesn't mean the cam is in the right place. Of course, it turned out to be the chain. |
Re: CJ5 misfires at high RPM/hard acceleration
matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your > suggestions: > > - Having the gas cap off made no difference. I actually don't have > any of the emissions stuff on it, so there's no canister, just the gas > tank to the pump. > - Having the coil's + lead hooked directly to the battery made no > difference, I tried switching the leads on the ballast resistor too > first to see if I had it hooked up wrong. I may be wrong, but I think > the ballast resistor leads can go either way? > - I tried what Roy suggested with interesting results. When I > advanced the engine to 10 or 15 degrees, it would run noticeably > better, but not perfect. I could actually get the secondaries to open > up on the carb before it crapped out, which I haven't been able to do > since the fuel pump change. I was grabbing at straws when I replaced > the vacuum advance. I could suck air right through it with my mouth > so I knew it was bad, that & having it plugged in at idle made no > difference in timing advance. When I have the new one plugged in, it > automatically advances it to about 10 BTDC at idle. I didn't see any > adjustments on it, but maybe that's what is wrong? I couldn't get the > engine started with it advanced so far when testing, I could only test > it out by having it started first & then advancing it. The idle was > terrible with a lot of misfiring at that point, if that means > anything. > - I've had a few people also tell me it's over carbureted, but that's > what has always been on it (my dad owned it for like about 15 years > before me) & it seemed to have ran fine for the longest time. That is > an interesting theory though that the old pump could have just been so > tired that it didn't put enough pressure through to put it at it's > full potential. I was considering a 500cfm 2-bbl holley if I had to > purchase one, but it sounds like that might be too much as well? To > clarify, the pump just started leaking when it went out, it didn't > seize up or anything, in fact I didn't know it was going bad until I > started getting sprayed with gas (there's no fenders, windshield, > etc). I don't know if I cleaned the jets out good enough when I > rebuilt the carb, so it's a possibility that part of the diaphragm got > stuck in it. it does seem to flow OK though when I look at the spray > coming out of the jets. > - The vacuum is very steady at idle, maybe 1hg of movement at most > from side to side. I have not performed a compression check, what > would that tell me if it were low? I don't have a compression tester > available so I'm not going to be able to do that one right away. > - The plugs are bosch platinums with a heat rating of 9. I'm not sure > what that equates to heat-wise though, is that a standard across all > plugs?\ > > Any suggestions on the distributor? I checked the springs & weights > of the centrifugal advance & they seem to be nice & responsive, but > then again, I'm not sure what they're supposed to look like. Should I > try replacing the entire distributor before I go crazy & take the > entire front of my engine apart for the timing chain or start messing > with the carb? Is there any way to test whether or not the timing > chain has slipped a tooth without actually looking at it? > > Thanks again guys, > > -Matt > I really think your problem is the timing, and could be caused by a few different things. Engines with aftermarket headers, cams, etc. usually like a little more timing. As long as you aren't experiencing ping and the starter doesn't kick back when the engine is hot, you're not hurting anything. An engine with not enough timing advance will do exactly what yours is doing. It will also seem like it is running rich because the fuel mixture is exiting the cylinder before is has had time to completely burn. the popping noise you're hearing is actually from the exhaust valve opening while the mixture is still burning. If you have access to a timing light with the dial adjustable advance on it, check the timing at idle with the vacuum advance disconnected, then rev the engine to about 3000-3500 RPM and check it there. It should have advance to about 30-34 degrees. If it is much less than this, then your mechanical advance is not functioning properly. My guess is that this is what is happening. IF you are not getting 30-34 degrees, you can test to see if the additional timing fixes the problem by advancing the timing to get about 30 degrees at 3000 RPM. One word of caution when doing this: you are compensating for a malfunctioning mechanical advance and will have a lot of timing at idle, so when you do your acceleration test like this, go light on the gas pedal to prevent a ton of pinging. There is a slight possibility that the outer ring on your balancer has slipped on the rubber ring between the outer ring and the hub. This is one thing that would explain the timing issue. An One thing that comes to mind that I have seen people forget during a Holley rebuild is the little needle check that goes in the fuel passage underneath the accelerator pump nozzle. If you leave that out, the engine vacuum at higher RPM can cause fuel to flow out the nozzle. It also causes other problems, which you don't seem to be experiencing, so it is probably in there. A 600 may not be ideal for a 304, but it can be made to run just fine. There are literally thousands of 302 Fords, 305 Chevys and 318 Mopars running Holey 600 carbs on them. I am assuming you probably have the Holley model 1850 (probably with a dash number after it) The number will be on the front of the choke horn. The problem with these carbs is that they are set up to run on a wide range of engines, and are very rarely perfect out of the box for your particular application. they are normally tuned a bit rich as far as jetting goes, but nothing extreme. If the engine runs the best with the mixture screws turned all the way in, or close to it, then obviously it is running too rich. Hook your vacuum gage up to manifold vacuum, which is any point below the throttle plates. Going by your vacuum reading, you're in the right spot now. Set your idle speed to the proper RPM and then remove the sight plug for the float level and adjust it so that the fuel level is just below the hole. By rocking the vehicle slightly, you should see the gas flow out of the sight hole just a little bit. Now using your vacuum gage, set the idle mixture screws to achieve the highest vacuum reading at idle. If the idle speed rises when you make adjustments, then reset the RPM to the correct level. A well tuned engine with a stock camshaft should have about 20" of vacuum, but an engine with a lot of miles will read less. Worn rings and valve seats will reduce vacuum. Try the timing test and see what happens. The carb tips I gave you will probably not affect your misfire condition, but were more for when you get to the point of tuning the carb. Chris |
Re: CJ5 misfires at high RPM/hard acceleration
matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your > suggestions: > > - Having the gas cap off made no difference. I actually don't have > any of the emissions stuff on it, so there's no canister, just the gas > tank to the pump. > - Having the coil's + lead hooked directly to the battery made no > difference, I tried switching the leads on the ballast resistor too > first to see if I had it hooked up wrong. I may be wrong, but I think > the ballast resistor leads can go either way? > - I tried what Roy suggested with interesting results. When I > advanced the engine to 10 or 15 degrees, it would run noticeably > better, but not perfect. I could actually get the secondaries to open > up on the carb before it crapped out, which I haven't been able to do > since the fuel pump change. I was grabbing at straws when I replaced > the vacuum advance. I could suck air right through it with my mouth > so I knew it was bad, that & having it plugged in at idle made no > difference in timing advance. When I have the new one plugged in, it > automatically advances it to about 10 BTDC at idle. I didn't see any > adjustments on it, but maybe that's what is wrong? I couldn't get the > engine started with it advanced so far when testing, I could only test > it out by having it started first & then advancing it. The idle was > terrible with a lot of misfiring at that point, if that means > anything. > - I've had a few people also tell me it's over carbureted, but that's > what has always been on it (my dad owned it for like about 15 years > before me) & it seemed to have ran fine for the longest time. That is > an interesting theory though that the old pump could have just been so > tired that it didn't put enough pressure through to put it at it's > full potential. I was considering a 500cfm 2-bbl holley if I had to > purchase one, but it sounds like that might be too much as well? To > clarify, the pump just started leaking when it went out, it didn't > seize up or anything, in fact I didn't know it was going bad until I > started getting sprayed with gas (there's no fenders, windshield, > etc). I don't know if I cleaned the jets out good enough when I > rebuilt the carb, so it's a possibility that part of the diaphragm got > stuck in it. it does seem to flow OK though when I look at the spray > coming out of the jets. > - The vacuum is very steady at idle, maybe 1hg of movement at most > from side to side. I have not performed a compression check, what > would that tell me if it were low? I don't have a compression tester > available so I'm not going to be able to do that one right away. > - The plugs are bosch platinums with a heat rating of 9. I'm not sure > what that equates to heat-wise though, is that a standard across all > plugs?\ > > Any suggestions on the distributor? I checked the springs & weights > of the centrifugal advance & they seem to be nice & responsive, but > then again, I'm not sure what they're supposed to look like. Should I > try replacing the entire distributor before I go crazy & take the > entire front of my engine apart for the timing chain or start messing > with the carb? Is there any way to test whether or not the timing > chain has slipped a tooth without actually looking at it? > > Thanks again guys, > > -Matt > I really think your problem is the timing, and could be caused by a few different things. Engines with aftermarket headers, cams, etc. usually like a little more timing. As long as you aren't experiencing ping and the starter doesn't kick back when the engine is hot, you're not hurting anything. An engine with not enough timing advance will do exactly what yours is doing. It will also seem like it is running rich because the fuel mixture is exiting the cylinder before is has had time to completely burn. the popping noise you're hearing is actually from the exhaust valve opening while the mixture is still burning. If you have access to a timing light with the dial adjustable advance on it, check the timing at idle with the vacuum advance disconnected, then rev the engine to about 3000-3500 RPM and check it there. It should have advance to about 30-34 degrees. If it is much less than this, then your mechanical advance is not functioning properly. My guess is that this is what is happening. IF you are not getting 30-34 degrees, you can test to see if the additional timing fixes the problem by advancing the timing to get about 30 degrees at 3000 RPM. One word of caution when doing this: you are compensating for a malfunctioning mechanical advance and will have a lot of timing at idle, so when you do your acceleration test like this, go light on the gas pedal to prevent a ton of pinging. There is a slight possibility that the outer ring on your balancer has slipped on the rubber ring between the outer ring and the hub. This is one thing that would explain the timing issue. An One thing that comes to mind that I have seen people forget during a Holley rebuild is the little needle check that goes in the fuel passage underneath the accelerator pump nozzle. If you leave that out, the engine vacuum at higher RPM can cause fuel to flow out the nozzle. It also causes other problems, which you don't seem to be experiencing, so it is probably in there. A 600 may not be ideal for a 304, but it can be made to run just fine. There are literally thousands of 302 Fords, 305 Chevys and 318 Mopars running Holey 600 carbs on them. I am assuming you probably have the Holley model 1850 (probably with a dash number after it) The number will be on the front of the choke horn. The problem with these carbs is that they are set up to run on a wide range of engines, and are very rarely perfect out of the box for your particular application. they are normally tuned a bit rich as far as jetting goes, but nothing extreme. If the engine runs the best with the mixture screws turned all the way in, or close to it, then obviously it is running too rich. Hook your vacuum gage up to manifold vacuum, which is any point below the throttle plates. Going by your vacuum reading, you're in the right spot now. Set your idle speed to the proper RPM and then remove the sight plug for the float level and adjust it so that the fuel level is just below the hole. By rocking the vehicle slightly, you should see the gas flow out of the sight hole just a little bit. Now using your vacuum gage, set the idle mixture screws to achieve the highest vacuum reading at idle. If the idle speed rises when you make adjustments, then reset the RPM to the correct level. A well tuned engine with a stock camshaft should have about 20" of vacuum, but an engine with a lot of miles will read less. Worn rings and valve seats will reduce vacuum. Try the timing test and see what happens. The carb tips I gave you will probably not affect your misfire condition, but were more for when you get to the point of tuning the carb. Chris |
Re: CJ5 misfires at high RPM/hard acceleration
matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your > suggestions: > > - Having the gas cap off made no difference. I actually don't have > any of the emissions stuff on it, so there's no canister, just the gas > tank to the pump. > - Having the coil's + lead hooked directly to the battery made no > difference, I tried switching the leads on the ballast resistor too > first to see if I had it hooked up wrong. I may be wrong, but I think > the ballast resistor leads can go either way? > - I tried what Roy suggested with interesting results. When I > advanced the engine to 10 or 15 degrees, it would run noticeably > better, but not perfect. I could actually get the secondaries to open > up on the carb before it crapped out, which I haven't been able to do > since the fuel pump change. I was grabbing at straws when I replaced > the vacuum advance. I could suck air right through it with my mouth > so I knew it was bad, that & having it plugged in at idle made no > difference in timing advance. When I have the new one plugged in, it > automatically advances it to about 10 BTDC at idle. I didn't see any > adjustments on it, but maybe that's what is wrong? I couldn't get the > engine started with it advanced so far when testing, I could only test > it out by having it started first & then advancing it. The idle was > terrible with a lot of misfiring at that point, if that means > anything. > - I've had a few people also tell me it's over carbureted, but that's > what has always been on it (my dad owned it for like about 15 years > before me) & it seemed to have ran fine for the longest time. That is > an interesting theory though that the old pump could have just been so > tired that it didn't put enough pressure through to put it at it's > full potential. I was considering a 500cfm 2-bbl holley if I had to > purchase one, but it sounds like that might be too much as well? To > clarify, the pump just started leaking when it went out, it didn't > seize up or anything, in fact I didn't know it was going bad until I > started getting sprayed with gas (there's no fenders, windshield, > etc). I don't know if I cleaned the jets out good enough when I > rebuilt the carb, so it's a possibility that part of the diaphragm got > stuck in it. it does seem to flow OK though when I look at the spray > coming out of the jets. > - The vacuum is very steady at idle, maybe 1hg of movement at most > from side to side. I have not performed a compression check, what > would that tell me if it were low? I don't have a compression tester > available so I'm not going to be able to do that one right away. > - The plugs are bosch platinums with a heat rating of 9. I'm not sure > what that equates to heat-wise though, is that a standard across all > plugs?\ > > Any suggestions on the distributor? I checked the springs & weights > of the centrifugal advance & they seem to be nice & responsive, but > then again, I'm not sure what they're supposed to look like. Should I > try replacing the entire distributor before I go crazy & take the > entire front of my engine apart for the timing chain or start messing > with the carb? Is there any way to test whether or not the timing > chain has slipped a tooth without actually looking at it? > > Thanks again guys, > > -Matt > I really think your problem is the timing, and could be caused by a few different things. Engines with aftermarket headers, cams, etc. usually like a little more timing. As long as you aren't experiencing ping and the starter doesn't kick back when the engine is hot, you're not hurting anything. An engine with not enough timing advance will do exactly what yours is doing. It will also seem like it is running rich because the fuel mixture is exiting the cylinder before is has had time to completely burn. the popping noise you're hearing is actually from the exhaust valve opening while the mixture is still burning. If you have access to a timing light with the dial adjustable advance on it, check the timing at idle with the vacuum advance disconnected, then rev the engine to about 3000-3500 RPM and check it there. It should have advance to about 30-34 degrees. If it is much less than this, then your mechanical advance is not functioning properly. My guess is that this is what is happening. IF you are not getting 30-34 degrees, you can test to see if the additional timing fixes the problem by advancing the timing to get about 30 degrees at 3000 RPM. One word of caution when doing this: you are compensating for a malfunctioning mechanical advance and will have a lot of timing at idle, so when you do your acceleration test like this, go light on the gas pedal to prevent a ton of pinging. There is a slight possibility that the outer ring on your balancer has slipped on the rubber ring between the outer ring and the hub. This is one thing that would explain the timing issue. An One thing that comes to mind that I have seen people forget during a Holley rebuild is the little needle check that goes in the fuel passage underneath the accelerator pump nozzle. If you leave that out, the engine vacuum at higher RPM can cause fuel to flow out the nozzle. It also causes other problems, which you don't seem to be experiencing, so it is probably in there. A 600 may not be ideal for a 304, but it can be made to run just fine. There are literally thousands of 302 Fords, 305 Chevys and 318 Mopars running Holey 600 carbs on them. I am assuming you probably have the Holley model 1850 (probably with a dash number after it) The number will be on the front of the choke horn. The problem with these carbs is that they are set up to run on a wide range of engines, and are very rarely perfect out of the box for your particular application. they are normally tuned a bit rich as far as jetting goes, but nothing extreme. If the engine runs the best with the mixture screws turned all the way in, or close to it, then obviously it is running too rich. Hook your vacuum gage up to manifold vacuum, which is any point below the throttle plates. Going by your vacuum reading, you're in the right spot now. Set your idle speed to the proper RPM and then remove the sight plug for the float level and adjust it so that the fuel level is just below the hole. By rocking the vehicle slightly, you should see the gas flow out of the sight hole just a little bit. Now using your vacuum gage, set the idle mixture screws to achieve the highest vacuum reading at idle. If the idle speed rises when you make adjustments, then reset the RPM to the correct level. A well tuned engine with a stock camshaft should have about 20" of vacuum, but an engine with a lot of miles will read less. Worn rings and valve seats will reduce vacuum. Try the timing test and see what happens. The carb tips I gave you will probably not affect your misfire condition, but were more for when you get to the point of tuning the carb. Chris |
Re: CJ5 misfires at high RPM/hard acceleration
matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your > suggestions: > > - Having the gas cap off made no difference. I actually don't have > any of the emissions stuff on it, so there's no canister, just the gas > tank to the pump. > - Having the coil's + lead hooked directly to the battery made no > difference, I tried switching the leads on the ballast resistor too > first to see if I had it hooked up wrong. I may be wrong, but I think > the ballast resistor leads can go either way? > - I tried what Roy suggested with interesting results. When I > advanced the engine to 10 or 15 degrees, it would run noticeably > better, but not perfect. I could actually get the secondaries to open > up on the carb before it crapped out, which I haven't been able to do > since the fuel pump change. I was grabbing at straws when I replaced > the vacuum advance. I could suck air right through it with my mouth > so I knew it was bad, that & having it plugged in at idle made no > difference in timing advance. When I have the new one plugged in, it > automatically advances it to about 10 BTDC at idle. I didn't see any > adjustments on it, but maybe that's what is wrong? I couldn't get the > engine started with it advanced so far when testing, I could only test > it out by having it started first & then advancing it. The idle was > terrible with a lot of misfiring at that point, if that means > anything. > - I've had a few people also tell me it's over carbureted, but that's > what has always been on it (my dad owned it for like about 15 years > before me) & it seemed to have ran fine for the longest time. That is > an interesting theory though that the old pump could have just been so > tired that it didn't put enough pressure through to put it at it's > full potential. I was considering a 500cfm 2-bbl holley if I had to > purchase one, but it sounds like that might be too much as well? To > clarify, the pump just started leaking when it went out, it didn't > seize up or anything, in fact I didn't know it was going bad until I > started getting sprayed with gas (there's no fenders, windshield, > etc). I don't know if I cleaned the jets out good enough when I > rebuilt the carb, so it's a possibility that part of the diaphragm got > stuck in it. it does seem to flow OK though when I look at the spray > coming out of the jets. > - The vacuum is very steady at idle, maybe 1hg of movement at most > from side to side. I have not performed a compression check, what > would that tell me if it were low? I don't have a compression tester > available so I'm not going to be able to do that one right away. > - The plugs are bosch platinums with a heat rating of 9. I'm not sure > what that equates to heat-wise though, is that a standard across all > plugs?\ > > Any suggestions on the distributor? I checked the springs & weights > of the centrifugal advance & they seem to be nice & responsive, but > then again, I'm not sure what they're supposed to look like. Should I > try replacing the entire distributor before I go crazy & take the > entire front of my engine apart for the timing chain or start messing > with the carb? Is there any way to test whether or not the timing > chain has slipped a tooth without actually looking at it? > > Thanks again guys, > > -Matt > I really think your problem is the timing, and could be caused by a few different things. Engines with aftermarket headers, cams, etc. usually like a little more timing. As long as you aren't experiencing ping and the starter doesn't kick back when the engine is hot, you're not hurting anything. An engine with not enough timing advance will do exactly what yours is doing. It will also seem like it is running rich because the fuel mixture is exiting the cylinder before is has had time to completely burn. the popping noise you're hearing is actually from the exhaust valve opening while the mixture is still burning. If you have access to a timing light with the dial adjustable advance on it, check the timing at idle with the vacuum advance disconnected, then rev the engine to about 3000-3500 RPM and check it there. It should have advance to about 30-34 degrees. If it is much less than this, then your mechanical advance is not functioning properly. My guess is that this is what is happening. IF you are not getting 30-34 degrees, you can test to see if the additional timing fixes the problem by advancing the timing to get about 30 degrees at 3000 RPM. One word of caution when doing this: you are compensating for a malfunctioning mechanical advance and will have a lot of timing at idle, so when you do your acceleration test like this, go light on the gas pedal to prevent a ton of pinging. There is a slight possibility that the outer ring on your balancer has slipped on the rubber ring between the outer ring and the hub. This is one thing that would explain the timing issue. An One thing that comes to mind that I have seen people forget during a Holley rebuild is the little needle check that goes in the fuel passage underneath the accelerator pump nozzle. If you leave that out, the engine vacuum at higher RPM can cause fuel to flow out the nozzle. It also causes other problems, which you don't seem to be experiencing, so it is probably in there. A 600 may not be ideal for a 304, but it can be made to run just fine. There are literally thousands of 302 Fords, 305 Chevys and 318 Mopars running Holey 600 carbs on them. I am assuming you probably have the Holley model 1850 (probably with a dash number after it) The number will be on the front of the choke horn. The problem with these carbs is that they are set up to run on a wide range of engines, and are very rarely perfect out of the box for your particular application. they are normally tuned a bit rich as far as jetting goes, but nothing extreme. If the engine runs the best with the mixture screws turned all the way in, or close to it, then obviously it is running too rich. Hook your vacuum gage up to manifold vacuum, which is any point below the throttle plates. Going by your vacuum reading, you're in the right spot now. Set your idle speed to the proper RPM and then remove the sight plug for the float level and adjust it so that the fuel level is just below the hole. By rocking the vehicle slightly, you should see the gas flow out of the sight hole just a little bit. Now using your vacuum gage, set the idle mixture screws to achieve the highest vacuum reading at idle. If the idle speed rises when you make adjustments, then reset the RPM to the correct level. A well tuned engine with a stock camshaft should have about 20" of vacuum, but an engine with a lot of miles will read less. Worn rings and valve seats will reduce vacuum. Try the timing test and see what happens. The carb tips I gave you will probably not affect your misfire condition, but were more for when you get to the point of tuning the carb. Chris |
Re: CJ5 misfires at high RPM/hard acceleration
matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your > suggestions: > The plugs are bosch platinums with a heat rating of 9 <snipped> 'All' the old Jeep engines 'I' personally have seen (and read about 'many') will 'NOT' run on Bosch platinum plugs. They foul up almost immediately. I would change those before doing anything else and put proper Champion truck plugs back into it. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) |
Re: CJ5 misfires at high RPM/hard acceleration
matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your > suggestions: > The plugs are bosch platinums with a heat rating of 9 <snipped> 'All' the old Jeep engines 'I' personally have seen (and read about 'many') will 'NOT' run on Bosch platinum plugs. They foul up almost immediately. I would change those before doing anything else and put proper Champion truck plugs back into it. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) |
Re: CJ5 misfires at high RPM/hard acceleration
matthew.nye@gmail.com wrote:
> Thanks for everyone's replies. Here's what I've done from your > suggestions: > The plugs are bosch platinums with a heat rating of 9 <snipped> 'All' the old Jeep engines 'I' personally have seen (and read about 'many') will 'NOT' run on Bosch platinum plugs. They foul up almost immediately. I would change those before doing anything else and put proper Champion truck plugs back into it. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) |
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