GMC Sierra C/K (Pre-1999):

Runs, Stumbles, then Dies

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# 1  3/26/2011 2:47 AM

mackillop89
New member
Registered: 3/26/2011
Posts: 2

Runs, Stumbles, then Dies

1989 GMC Sierra C1500, 350cc 5.7 L V-8, 2wd.
It starts up okay, then it stumbles and starts cutting out after approximately 30 seconds or less, then it will die whatever I do (step on the accelerator, brake, or nothing.) I can start it an infinite number of times, only the time span between the starting and the stumbling gets shorter.
It does this whether I start in park or neutral. I'm also burning oil and possibly antifreeze as well, although those may be a separate problem. I haven't been able to figure out where the oil leak is coming from.
To be honest, the vehicle is a mess, but as long as I can keep it running, I'm fine. I'm going into the military in less than 3 months, so I've got to make this work for the time being. I'm hoping to have this fixed by this weekend. It just died on me a few hours ago.
Before this occurred, normally I can hear a whirring sound when I put the key in the ignition position AND after I turn the truck off. But the last few times before it died, I haven't heard the whirring noise. I'm thinking it might be that the fuel pump has gone bad, but I'm not sure.
Any suggestions or help?

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# 2  3/26/2011 3:33 AM

TechHelp2
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Registered: 11/24/2009
Posts: 1299

Re: Runs, Stumbles, then Dies

You could be on the right path.

I would check the fuel filter first. When was the last time it was changed?

Because it starts gives me the indication that the fuel pump relay is working, but check it anyway to be sure.

Check the fuel pressure when it is running. Also check to see if you have the two second prime when you turn the key on. After 2 seconds the pressure should be 9-13 lbs.

The fuel pressure should be about 9-13 lbs running also.

The fuel pressure regulator could also be at fault. It could be stuck closed. Check this only if all other tests are negative.

Smoke is a telltale sign. White is usually antifreeze, oil has a bluish color. If either problem is bad it could cause some symptoms but you would probably smoke out the neighborhood before you would notice any stalling problems.

Check the fuel filter and fuel pressure first and let us know how you made out.


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# 3  4/4/2011 9:28 PM

mackillop89
New member
Registered: 3/26/2011
Posts: 2

Re: Runs, Stumbles, then Dies

Okay, I replaced the fuel pump filter, but it still dies on me. It did run a little longer, and this time it did NOT stumble before it died. It just wheezed out, backfired once, and quit running. I was able to start it again and make it home. But the problem is still there.
I am not sure how to check the fuel pressure. A neighbor suggested the throttle body or the fuel injectors could be bad.
What do I do next?

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# 4  4/4/2011 11:03 PM

TechHelp2
Administrator
Registered: 11/24/2009
Posts: 1299

Re: Runs, Stumbles, then Dies

Knowing the fuel pressure is important. Once you know that number then we can continue. The fuel pressure is gauge is tied into the fuel system usually at the fuel filter if there isn't any schrader valve is installed in the fuel line.

Having a scanner put on the vehicle can also give important data that can help diagnose the stalling problem.

A clogged exhaust system can give you the same symptoms. The catalytic converter is included in the exhaust system. A back pressure test is required to help eliminate the exhaust system as a cause of the problem.

Until you get this information we can't go much further.

Get back to us when you can.


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