Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
 

I resemble that!
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

DougW wrote:
>
> You can put a pressure gauge in the O2 sensor hole and some of the old
> farts would say, real jeeps don't have catalytic converters. :)
>
> --
> rbg

Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
 

I resemble that!
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

DougW wrote:
>
> You can put a pressure gauge in the O2 sensor hole and some of the old
> farts would say, real jeeps don't have catalytic converters. :)
>
> --
> rbg

Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
 

In message <151220030900494970%RhmpL33@nospam.net>, "Rich Hampel" wrote:

>
>Its a @ 2SE (non-Kalyfornia)

Good, that eliminates a problem with electronic controls.
>
>Cam timing is Correct

If you say so....

>
>Yup, I know (now) that changing/replacing intake gaskets has been a
>waste of time.
>With low vac the engine runs retarded hence rich at normal highway rpm,
>at low vac all the dampers in the air cleaner close ... also make it
>run rich (but I have them locked out at the moment).

Two or three posts have mentioned restricted exhaust now, and you haven't
responded to them. Have you checked this? A *symptom* of plugged exhaust would
be low vacuum. This would cause a couple of problems.

1) If you can't get the all of the burned gas out, you can't get a full charge
of fuel/air in for the next cycle.

2) That vehicle is equipped with a back pressure EGR valve. Too much back
pressure could cause too much EGR action. Too much exhaust gas in the
combustion chamber displaces too much of the air and fuel needed for decent
combustion.

Once again, have you checked for restricted exhaust?


>
>In article <vkqqtv8r9gf3qcacg8k4c428dbeo3fj2is@4ax.com>, bllsht
><nospam@invaliddot.net> wrote:
>
>> You're still thinking backwards. Vacuum is low because it runs like ----. It
>> doesn't run like ---- because vacuum is low. You need to find out why it's
>> running so bad . Is it a 2SE or E2SE carb? Have you checked cam timing?
>>
>> You're wasting your time changing intake gaskets. If they leak the engine
>> runs
>> lean. If you're "depositing lots of carbon in the combustion chambers", it's
>> too rich.
>>
>> In message <141220032235242637%RhmpL33@nospam.net>, "Rich Hampel" wrote:
>>
>> >I'M TOTALLY STUMPED with the vacuum output on 2.8L GM 6 in an XJ
>> >Cherokee
>> >
>> >Kindly offer opinions on low vacuum output on 2.8L in '86 XJ Cherokee
>> >Engine has 3000 mi. - was a GM 'Johnson' rebuild' (longblock.)
>> >Compression is 130-150 psi (cold)
>> >Replaced intake manifold gasket 3 times.
>> >Ign. Timing at 12 deg BTDC (centrifugal adv. is full operative).
>> >Have swapped ign. module in dist w/ no change.
>> >No idle change with propane or WD40 along carb base or intake edges.
>> >Carb change makes NO diff. (have two vari-jet 2bbls).
>> >Best vacuum I can get at idle is 13-14 in. hg. vac. (steady reading -
>> >no apparent valve 'bounce' on the vac gauge) ... not enough vac to
>> >run EGR, barely enough to run distributor vac. advance .... or most of
>> >the 'topside' vac controlled emission controls are sloooow to react
>> >(driveability). I know I need at least 18"hg. vac to0 make the
>> >emission controls, etc. work ... cant get it.
>> >Brake booster is weak due to low vac. .... clamped vac hose to booster
>> >makes NO difference.
>> >Not enough vacuum to hold proper static level of gasoline in carb bowl
>> >(therefore stalls at hard left turn). Float valve NOT sticking, etc.
>> >All vacuum rubber lines and devices intact without leaks (?) .... can
>> >clamp down with pliers on lines without engine stutter (except pcv and
>> >carb bowl vac line). When PCV / Carb Bowl vac line is pinched only get
>> >1/2" addtl. vacuum.
>> >The intake manifold isnt warped ( I've checked it 3 times now ... when
>> >replacing intake manifold gaskets.)
>> >Have not had good vacuum since I replaced with this engine.
>> >
>> >(Anyone know if there should be an vac. orfice plate between PCV ( and
>> >carb. bowl) and intake manifold) What would be the volumetric vac.
>> >flow for the PCV ?
>> >
>> >I'm totally out of ideas.
>> >Engine vac. is so low that Ive lost control of carb and Im depositing
>> >lots of carbon in the combustion chambers, fuel economy is off by 5-6
>> >mpg.
>> >
>> >Thanks for ANY input.
>>

Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
 

In message <151220030900494970%RhmpL33@nospam.net>, "Rich Hampel" wrote:

>
>Its a @ 2SE (non-Kalyfornia)

Good, that eliminates a problem with electronic controls.
>
>Cam timing is Correct

If you say so....

>
>Yup, I know (now) that changing/replacing intake gaskets has been a
>waste of time.
>With low vac the engine runs retarded hence rich at normal highway rpm,
>at low vac all the dampers in the air cleaner close ... also make it
>run rich (but I have them locked out at the moment).

Two or three posts have mentioned restricted exhaust now, and you haven't
responded to them. Have you checked this? A *symptom* of plugged exhaust would
be low vacuum. This would cause a couple of problems.

1) If you can't get the all of the burned gas out, you can't get a full charge
of fuel/air in for the next cycle.

2) That vehicle is equipped with a back pressure EGR valve. Too much back
pressure could cause too much EGR action. Too much exhaust gas in the
combustion chamber displaces too much of the air and fuel needed for decent
combustion.

Once again, have you checked for restricted exhaust?


>
>In article <vkqqtv8r9gf3qcacg8k4c428dbeo3fj2is@4ax.com>, bllsht
><nospam@invaliddot.net> wrote:
>
>> You're still thinking backwards. Vacuum is low because it runs like ----. It
>> doesn't run like ---- because vacuum is low. You need to find out why it's
>> running so bad . Is it a 2SE or E2SE carb? Have you checked cam timing?
>>
>> You're wasting your time changing intake gaskets. If they leak the engine
>> runs
>> lean. If you're "depositing lots of carbon in the combustion chambers", it's
>> too rich.
>>
>> In message <141220032235242637%RhmpL33@nospam.net>, "Rich Hampel" wrote:
>>
>> >I'M TOTALLY STUMPED with the vacuum output on 2.8L GM 6 in an XJ
>> >Cherokee
>> >
>> >Kindly offer opinions on low vacuum output on 2.8L in '86 XJ Cherokee
>> >Engine has 3000 mi. - was a GM 'Johnson' rebuild' (longblock.)
>> >Compression is 130-150 psi (cold)
>> >Replaced intake manifold gasket 3 times.
>> >Ign. Timing at 12 deg BTDC (centrifugal adv. is full operative).
>> >Have swapped ign. module in dist w/ no change.
>> >No idle change with propane or WD40 along carb base or intake edges.
>> >Carb change makes NO diff. (have two vari-jet 2bbls).
>> >Best vacuum I can get at idle is 13-14 in. hg. vac. (steady reading -
>> >no apparent valve 'bounce' on the vac gauge) ... not enough vac to
>> >run EGR, barely enough to run distributor vac. advance .... or most of
>> >the 'topside' vac controlled emission controls are sloooow to react
>> >(driveability). I know I need at least 18"hg. vac to0 make the
>> >emission controls, etc. work ... cant get it.
>> >Brake booster is weak due to low vac. .... clamped vac hose to booster
>> >makes NO difference.
>> >Not enough vacuum to hold proper static level of gasoline in carb bowl
>> >(therefore stalls at hard left turn). Float valve NOT sticking, etc.
>> >All vacuum rubber lines and devices intact without leaks (?) .... can
>> >clamp down with pliers on lines without engine stutter (except pcv and
>> >carb bowl vac line). When PCV / Carb Bowl vac line is pinched only get
>> >1/2" addtl. vacuum.
>> >The intake manifold isnt warped ( I've checked it 3 times now ... when
>> >replacing intake manifold gaskets.)
>> >Have not had good vacuum since I replaced with this engine.
>> >
>> >(Anyone know if there should be an vac. orfice plate between PCV ( and
>> >carb. bowl) and intake manifold) What would be the volumetric vac.
>> >flow for the PCV ?
>> >
>> >I'm totally out of ideas.
>> >Engine vac. is so low that Ive lost control of carb and Im depositing
>> >lots of carbon in the combustion chambers, fuel economy is off by 5-6
>> >mpg.
>> >
>> >Thanks for ANY input.
>>

Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
 

In message <151220030900494970%RhmpL33@nospam.net>, "Rich Hampel" wrote:

>
>Its a @ 2SE (non-Kalyfornia)

Good, that eliminates a problem with electronic controls.
>
>Cam timing is Correct

If you say so....

>
>Yup, I know (now) that changing/replacing intake gaskets has been a
>waste of time.
>With low vac the engine runs retarded hence rich at normal highway rpm,
>at low vac all the dampers in the air cleaner close ... also make it
>run rich (but I have them locked out at the moment).

Two or three posts have mentioned restricted exhaust now, and you haven't
responded to them. Have you checked this? A *symptom* of plugged exhaust would
be low vacuum. This would cause a couple of problems.

1) If you can't get the all of the burned gas out, you can't get a full charge
of fuel/air in for the next cycle.

2) That vehicle is equipped with a back pressure EGR valve. Too much back
pressure could cause too much EGR action. Too much exhaust gas in the
combustion chamber displaces too much of the air and fuel needed for decent
combustion.

Once again, have you checked for restricted exhaust?


>
>In article <vkqqtv8r9gf3qcacg8k4c428dbeo3fj2is@4ax.com>, bllsht
><nospam@invaliddot.net> wrote:
>
>> You're still thinking backwards. Vacuum is low because it runs like ----. It
>> doesn't run like ---- because vacuum is low. You need to find out why it's
>> running so bad . Is it a 2SE or E2SE carb? Have you checked cam timing?
>>
>> You're wasting your time changing intake gaskets. If they leak the engine
>> runs
>> lean. If you're "depositing lots of carbon in the combustion chambers", it's
>> too rich.
>>
>> In message <141220032235242637%RhmpL33@nospam.net>, "Rich Hampel" wrote:
>>
>> >I'M TOTALLY STUMPED with the vacuum output on 2.8L GM 6 in an XJ
>> >Cherokee
>> >
>> >Kindly offer opinions on low vacuum output on 2.8L in '86 XJ Cherokee
>> >Engine has 3000 mi. - was a GM 'Johnson' rebuild' (longblock.)
>> >Compression is 130-150 psi (cold)
>> >Replaced intake manifold gasket 3 times.
>> >Ign. Timing at 12 deg BTDC (centrifugal adv. is full operative).
>> >Have swapped ign. module in dist w/ no change.
>> >No idle change with propane or WD40 along carb base or intake edges.
>> >Carb change makes NO diff. (have two vari-jet 2bbls).
>> >Best vacuum I can get at idle is 13-14 in. hg. vac. (steady reading -
>> >no apparent valve 'bounce' on the vac gauge) ... not enough vac to
>> >run EGR, barely enough to run distributor vac. advance .... or most of
>> >the 'topside' vac controlled emission controls are sloooow to react
>> >(driveability). I know I need at least 18"hg. vac to0 make the
>> >emission controls, etc. work ... cant get it.
>> >Brake booster is weak due to low vac. .... clamped vac hose to booster
>> >makes NO difference.
>> >Not enough vacuum to hold proper static level of gasoline in carb bowl
>> >(therefore stalls at hard left turn). Float valve NOT sticking, etc.
>> >All vacuum rubber lines and devices intact without leaks (?) .... can
>> >clamp down with pliers on lines without engine stutter (except pcv and
>> >carb bowl vac line). When PCV / Carb Bowl vac line is pinched only get
>> >1/2" addtl. vacuum.
>> >The intake manifold isnt warped ( I've checked it 3 times now ... when
>> >replacing intake manifold gaskets.)
>> >Have not had good vacuum since I replaced with this engine.
>> >
>> >(Anyone know if there should be an vac. orfice plate between PCV ( and
>> >carb. bowl) and intake manifold) What would be the volumetric vac.
>> >flow for the PCV ?
>> >
>> >I'm totally out of ideas.
>> >Engine vac. is so low that Ive lost control of carb and Im depositing
>> >lots of carbon in the combustion chambers, fuel economy is off by 5-6
>> >mpg.
>> >
>> >Thanks for ANY input.
>>

Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
 

On Tue, 16 Dec 2003 04:29:09 UTC bllsht <nospam@invaliddot.net> wrote:

> In message <151220030900494970%RhmpL33@nospam.net>, "Rich Hampel" wrote:
>
> >
> >Its a @ 2SE (non-Kalyfornia)
>
> Good, that eliminates a problem with electronic controls.
> >
> >Cam timing is Correct
>
> If you say so....
>
> >
> >Yup, I know (now) that changing/replacing intake gaskets has been a
> >waste of time.
> >With low vac the engine runs retarded hence rich at normal highway rpm,
> >at low vac all the dampers in the air cleaner close ... also make it
> >run rich (but I have them locked out at the moment).
>
> Two or three posts have mentioned restricted exhaust now, and you haven't
> responded to them. Have you checked this? A *symptom* of plugged exhaust would
> be low vacuum. This would cause a couple of problems.
>
> 1) If you can't get the all of the burned gas out, you can't get a full charge
> of fuel/air in for the next cycle.
>
> 2) That vehicle is equipped with a back pressure EGR valve. Too much back
> pressure could cause too much EGR action. Too much exhaust gas in the
> combustion chamber displaces too much of the air and fuel needed for decent
> combustion.
>
> Once again, have you checked for restricted exhaust?

Can you put a number on the expected or acceptable back pressure
(pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen
lots of talk about excessive back pressure, but just what constitutes
excessive??

--
Will Honea <whonea@codenet.net>

Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
 

On Tue, 16 Dec 2003 04:29:09 UTC bllsht <nospam@invaliddot.net> wrote:

> In message <151220030900494970%RhmpL33@nospam.net>, "Rich Hampel" wrote:
>
> >
> >Its a @ 2SE (non-Kalyfornia)
>
> Good, that eliminates a problem with electronic controls.
> >
> >Cam timing is Correct
>
> If you say so....
>
> >
> >Yup, I know (now) that changing/replacing intake gaskets has been a
> >waste of time.
> >With low vac the engine runs retarded hence rich at normal highway rpm,
> >at low vac all the dampers in the air cleaner close ... also make it
> >run rich (but I have them locked out at the moment).
>
> Two or three posts have mentioned restricted exhaust now, and you haven't
> responded to them. Have you checked this? A *symptom* of plugged exhaust would
> be low vacuum. This would cause a couple of problems.
>
> 1) If you can't get the all of the burned gas out, you can't get a full charge
> of fuel/air in for the next cycle.
>
> 2) That vehicle is equipped with a back pressure EGR valve. Too much back
> pressure could cause too much EGR action. Too much exhaust gas in the
> combustion chamber displaces too much of the air and fuel needed for decent
> combustion.
>
> Once again, have you checked for restricted exhaust?

Can you put a number on the expected or acceptable back pressure
(pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen
lots of talk about excessive back pressure, but just what constitutes
excessive??

--
Will Honea <whonea@codenet.net>

Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
 

On Tue, 16 Dec 2003 04:29:09 UTC bllsht <nospam@invaliddot.net> wrote:

> In message <151220030900494970%RhmpL33@nospam.net>, "Rich Hampel" wrote:
>
> >
> >Its a @ 2SE (non-Kalyfornia)
>
> Good, that eliminates a problem with electronic controls.
> >
> >Cam timing is Correct
>
> If you say so....
>
> >
> >Yup, I know (now) that changing/replacing intake gaskets has been a
> >waste of time.
> >With low vac the engine runs retarded hence rich at normal highway rpm,
> >at low vac all the dampers in the air cleaner close ... also make it
> >run rich (but I have them locked out at the moment).
>
> Two or three posts have mentioned restricted exhaust now, and you haven't
> responded to them. Have you checked this? A *symptom* of plugged exhaust would
> be low vacuum. This would cause a couple of problems.
>
> 1) If you can't get the all of the burned gas out, you can't get a full charge
> of fuel/air in for the next cycle.
>
> 2) That vehicle is equipped with a back pressure EGR valve. Too much back
> pressure could cause too much EGR action. Too much exhaust gas in the
> combustion chamber displaces too much of the air and fuel needed for decent
> combustion.
>
> Once again, have you checked for restricted exhaust?

Can you put a number on the expected or acceptable back pressure
(pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen
lots of talk about excessive back pressure, but just what constitutes
excessive??

--
Will Honea <whonea@codenet.net>

Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
 

DougW wrote:
>
> Mike Romain did pass the time by typing:
> > As someone else mentioned, a plugged up catalytic converter can cause
> > your symptoms. It does happen, the guts can come loose blocking the
> > passages.
> >
> > The only way I know to test for it is to unhook the exhaust before the
> > cat or at the manifold and see if the vacuum comes up.
>
> You can put a pressure gauge in the O2 sensor hole and some of the old
> farts would say, real jeeps don't have catalytic converters. :)
>
> --
> rbg

Up here in Canada, an 86 does not need a cat to pass emissions. Well...
I isn't 'looked' for on the visual test, but if it won't pass, then a
cat might help it....

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Re: Vacuum pressure on '86 2.8L --- TOTALLY STUMPED
 

DougW wrote:
>
> Mike Romain did pass the time by typing:
> > As someone else mentioned, a plugged up catalytic converter can cause
> > your symptoms. It does happen, the guts can come loose blocking the
> > passages.
> >
> > The only way I know to test for it is to unhook the exhaust before the
> > cat or at the manifold and see if the vacuum comes up.
>
> You can put a pressure gauge in the O2 sensor hole and some of the old
> farts would say, real jeeps don't have catalytic converters. :)
>
> --
> rbg

Up here in Canada, an 86 does not need a cat to pass emissions. Well...
I isn't 'looked' for on the visual test, but if it won't pass, then a
cat might help it....

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's