|
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 |
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