Stalling problems In warm Temperature

20

Asked by Oct 06, 2015 at 07:13 AM about the 1991 GMC Sierra 1500 C1500 SLX Standard Cab LB

Question type: Maintenance & Repair

I have a 1991 GMC Sierra 1500.truck runs great
idle's good in the morning when it's cool outside.  
In  the afternoon when it warms up. It takes 3 to 4
tries to start it in to keep it running . It stalls out
one time while I'm driving or when I'm stop before
I make it home.any help will be appreciated
thanks

43 Answers

52,215

Sounds like a fuel pressure problem, I cant remember what the fuel pressure should be on that one.

1 out of 1 people think this is helpful.
Best Answer
20

Checked fuel pressure a few weeks ago in front of fuel filter couldn't get any reading didn't know if I was doing it correctly . But when unhooked fuel rail from TBI could see fuel squirting out when I turn the key . Maybe it's not getting enough pressure ?

20

Maybe bad fuel pump

52,215

Sorry I had some computer problems, and yes your symptoms indicate a failing fuel pump. Checking it in front of the fuel filter is ok, normally in the line up by the TBI? or CPI. Like I said I cant remember what is on there so, TBI pressure should be 12 lbs. min. Central Port Injection, 56-62 lbs.

20

also connected it between TBI and fuel line and couldn't get a reading they are either. I also notice the oil pressure sender or sensor . Located just above the Oil filter does not have a wiring harness connected to it. Could this effect any problems with the fuel pump ?

20

Also where is the central port injection located

52,215

Ok here, I'll try to explain the best I can. Your injection system must be a TBI (Throttle Body Injection) were there are 2 injectors under the air canister. Is that what it looks like? When you checked fuel pressure between the TBI and fuel line, was the engine running? You need 9 to 12 lbs. Central Port Injection is another style of fuel injection. It again is at the center of the intake manifold, which the air filter is off to the side, and there is a cover over the air intake, it has one large bore in the center. Never the less if you checked fuel pressure and not reading anything and the motor runs, you have to be checking it wrong because the motor would not run. That wire would not have anything to do with fuel pressure, but it need to go somewhere as the computer controls the engine by sensors. Oil pressure sending unit is part of the system.

20

Yes it is a tbi. I hooked a adapter between the TBI and the fuel line and then screwed on the fuel pressure tester. turn the key a few times to build up pressure.then let it run. Still no pressure reading . Am I doing anything wrong???? Hook it up at the port on my Tahoe and it worked fine .

52,215

No, it does not sound like you are doing anything wrong. But what you should do is check fuel pump pressure by dead heading the gage into the line. Your vehicle would not run as there is no fuel. I say this because there is a fuel pressure regulator in the TBI that the spring gets weak, and need rebuilding. They make rebuild kits for the TBI, and is relatively simple to do. Dead heading the fuel line with the pressure gage in it to read, should show a min. of 12 lbs. and up to 20 lbs.

20

Thanks I'll try that and let you know

20

Thanks I'll try that and let you know

20

OK finally got a chance to test fuel pressure again. And was able to get a reading. With TBI fuel pressure adapter. No pressure with key just turned. With truck running 10 psi. With truck running and return line blocked 12 psi. Seems like I have a week fuel pump.

52,215

Ok, there you go. It is not fun to change, have to drop gas tank, or cut a hole in the box floor, my buddy likes taking the box off to get at it. May want some one to do it, I had some one do mine as I did not want to deal with it. If the truck runs threw sault in the winter, wise to change the sending unit while you or they are doing it.

20

Lol kind of thought it might have been the fuel pump so three weeks ago while on vacation pulled liner off and cut hole in box already. So I guess the next step will be changing the fuel pump and sending unit. Thanks a lot for your help

52,215

Ok, you are welcome

20

No I didn't didn't know how to hook it up that way

52,215

Just use a rubber fuel line and a bolt clamped on one end, anything to block the flow of fuel, and just turn the key on to run the pump.

20

OK I'll try that too

52,215

Ok are we going to get somewhere with this today? Dead head the fuel pressure gage, run line in, No Out flow. The reason is I am concerned about the fuel regulator in the TBI.

20

Yes I'm going to try but when I tested the fuel pressure I blocked the return line off with the clamp so no fuel will go back through and read 11 psi which if something was wrong with the fuel regulator should've went above 15 and it had really no change that's what I'm thinking there's no problem with the fuel pressure regulator

52,215

I know there may be a problem with the regulator, but we need to know what pressure the fuel pump is putting out, NOT RUNING THREW THE TBI. Trying to isolate the problem and see if there are 2 problems or not.

20

I have to get an adapter for the fuel pressure tester it has the Schrader valve connector on the end.unless you know another way to do it

20

You didn't understand my answer but thanks for the help anyway

52,215

Your Welcome, Just venting... gets a little frustrating, ask away what you need. Sorry.

52,215

I read again what you said I did miss understand Very Sorry, ok ? Schrader connector on the pressure gage, didn't it come with other fittings? Something to screw into the fuel filter then to a fuel hose? Anything?

20

The fuel pressure tester I have is a loaner from AutoZone. At the end of the hose it has the piece that u screw on an adapter or a Schrader valve connector. I cannot take that piece off to go straight in to the fuel line I would either have to get another without the piece or some type of an adapter. So when I go to work Monday I will borrow one from one of the mechanics at work.

20

http://www.finditparts.com/product s/1860663/otc-tools-and- equipment-5630? srcid=CHL01SCL010-Npla-Dmdt- Gusa-Svbr-Mmuu- K1860663&gclid=CNyr7rCUucgCFd YWHwodL1MJ7w

20

That is the type I have

20

http://m.summitracing.com/parts/an m-cp7803? seid=srese1&gclid=CJH7o_iUucgC FYuRHwodlsYMzw

20

This is the type I need

20

No it didn't have any other adapters besides the TBI adapter to fit

148,985

What we need to know is what engine? Here is a chart, find yours and we can go from there- http://jameshalderman.com/links/book_adv_eng_perf_5/s_and_c/Fuel_Pressure_Specifications.pdf

52,215

Ok thanks, I'm just trying to make sure if we are dealing with 1 or 2 problems. Chances are it is just the fuel pump, but you seem like you are wanting to learn, these are the steps in eliminating grief when there are several possibilities to a problem. You must not need to drive this,? as you seem to be working on this for awhile now.

1 out of 1 people think this is helpful.
20

Well I use it for back-and-forth to work. And yes I am trying to learn about it's a second vehicle. It keeps me busy trying to figure it out. Trying to get it ready for the winter .

1 out of 1 people think this is helpful.
20

It's a 5.0 tbi they say 9 to 13 PSI deadhead.I will check that as soon as I get the other tester

1 out of 1 people think this is helpful.
52,215

Good morning there Mike, New day, and that dead head pressure should be 13 min. to 15 lbs. We'll get you threw this...

20

OK thanks I will let you know when I get to that point

52,215

Hows it going there Mike? Still here to help...

20

Fuel pump was delivered Thursday.was not the correct pump so I sent it back Friday. Correct pump should be here Monday

20

Only got 3 PSI out of deadhead

52,215

Great! Keep me updated, have a good weekend....

20

Replaced fuel pump truck runs great now thanks for all the help

52,215

Thanks for the reply.

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