Fuel pressure question

scavanger · 10-31-2009, 12:07 PM

95 GMC 5.7 TBI could someone tell me what fuel pressure is supposed to be ?

Thank you
Scav.

leolkfrm · 10-31-2009, 12:14 PM

12-16psi for tbi

scavanger · 10-31-2009, 12:22 PM

Wheeww. that's a relief , I have 16 lbs running. I borrowed one of those adapters with the shrader valve to put in place of fuel filter.
Have now eliminated fuel as my running problem.
Anyone ever hear of the distributer housing breaking and causing problems ?
I think I read here that the dist. module has some control over the TBI ???? I think I am getting close on this , keeps pointing at coil or module.

Is there a ohm specification for the coil?

Scav.

bradrhale · 10-31-2009, 03:00 PM

you do have an ignition module under the dizzy that can control fuel and or spark. if your dizzy cap is broken, replace it. they never function right even with the smallest crack. is it spraying fuel out of the injectors??

scavanger · 10-31-2009, 07:06 PM

Cap ,rotor and wires are good. I was told by a shop that the dist themselves could crack. Wondered if anyone else had heard that or experienced it.
If the module actually controls the TBI then it is a place for me to be looking at.
As stated in my other thread. It starts well and runs but when it warms up it runs poorly.

Scav.

BernieB · 10-31-2009, 07:35 PM

When ignition modules "go" it's usually from heat. They'll start getting intermittent at first, then cut out completely when they get hot enough. If you've eliminated other possibilities then this is certainly a possible cause. Be aware though, a bad coil can have identical symptoms.

scavanger · 10-31-2009, 08:51 PM

I will have to try to find a coil I can borrow.
Hate to buy a new one if that isn't the problem. Same with the module .
A bad coil wouldn't necessarily cause hard start when hot ?

Scav.

BernieB · 10-31-2009, 10:57 PM

Quote:

Originally Posted by scavanger

I will have to try to find a coil I can borrow.
Hate to buy a new one if that isn't the problem. Same with the module .
A bad coil wouldn't necessarily cause hard start when hot ?

Scav.

It could, if it's throwing a weak spark.

chengny · 11-01-2009, 01:00 AM

I will have to try to find a coil I can borrow.
Hate to buy a new one if that isn't the problem. Same with the module .
A bad coil wouldn't necessarily cause hard start when hot ?

I have often wondered that too. Can a coil become "weak", or is it a go/nogo situation?

I think that the conventional wisdom is that if the coil produces a bright blue spark that can jump a sufficient gap, it is good.

But since you are determined to do this the right way:

scavanger · 11-01-2009, 08:31 AM

That's great! Just what I needed. I think what I will do is test it cold , if it tests good I will try it hot.
I also will need to test the temp sensor just to be sure. I checked the TPS and that was right on. Are the values on the temp sensor pretty much standard through out the OBDI ?
I have the 90 Corvette FSM that I could go by.
Thank you .
Scav.

10-31-2009, 12:07 PM	#1
scavanger Senior Member Join Date: May 2007 Posts: 262	Fuel pressure question 95 GMC 5.7 TBI could someone tell me what fuel pressure is supposed to be ? Thank you Scav.

10-31-2009, 12:14 PM	#2
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 4,300	12-16psi for tbi __________________ 4 wheels move the body 2 wheels move the soul B.W.A.I

10-31-2009, 12:22 PM	#3
scavanger Senior Member Join Date: May 2007 Posts: 262	Wheeww. that's a relief , I have 16 lbs running. I borrowed one of those adapters with the shrader valve to put in place of fuel filter. Have now eliminated fuel as my running problem. Anyone ever hear of the distributer housing breaking and causing problems ? I think I read here that the dist. module has some control over the TBI ???? I think I am getting close on this , keeps pointing at coil or module. Is there a ohm specification for the coil? Scav. Last edited by scavanger; 10-31-2009 at 01:44 PM.

10-31-2009, 07:06 PM	#5
scavanger Senior Member Join Date: May 2007 Posts: 262	Cap ,rotor and wires are good. I was told by a shop that the dist themselves could crack. Wondered if anyone else had heard that or experienced it. If the module actually controls the TBI then it is a place for me to be looking at. As stated in my other thread. It starts well and runs but when it warms up it runs poorly. Scav. Last edited by scavanger; 10-31-2009 at 07:24 PM.

10-31-2009, 07:35 PM	#6
BernieB Senior Member Join Date: Jul 2009 Location: Fredericksburg, VA Posts: 1,902	When ignition modules "go" it's usually from heat. They'll start getting intermittent at first, then cut out completely when they get hot enough. If you've eliminated other possibilities then this is certainly a possible cause. Be aware though, a bad coil can have identical symptoms. __________________ If the guys who design 'em had to take one home, use it every day for 2 years, and do all the maint and repairs themselves, cars would have a button on the dash to change the oil, filters & plugs.

10-31-2009, 03:00 PM	#4
bradrhale Senior Moderator Join Date: Apr 2006 Location: Texas Posts: 8,025	you do have an ignition module under the dizzy that can control fuel and or spark. if your dizzy cap is broken, replace it. they never function right even with the smallest crack. is it spraying fuel out of the injectors??

10-31-2009, 08:51 PM	#7
scavanger Senior Member Join Date: May 2007 Posts: 262	I will have to try to find a coil I can borrow. Hate to buy a new one if that isn't the problem. Same with the module . A bad coil wouldn't necessarily cause hard start when hot ? Scav.

11-01-2009, 08:31 AM	#10
scavanger Senior Member Join Date: May 2007 Posts: 262	That's great! Just what I needed. I think what I will do is test it cold , if it tests good I will try it hot. I also will need to test the temp sensor just to be sure. I checked the TPS and that was right on. Are the values on the temp sensor pretty much standard through out the OBDI ? I have the 90 Corvette FSM that I could go by. Thank you . Scav.

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