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'95 GMC 1500 issue
01-23-2014, 12:32 PM
Post: #1
'95 GMC 1500 issue
Im brand new here, thought I'd see if you guys were familiar with the problem Im having with my truck. I have a suspicion it could be an easy fix so I thought Id turn to this community for help, otherwise I'll have to pay a tow truck to haul it to the nearest mechanic and have him gouge me for hours of diagnosis and watch as my bill runs up after throwing parts at it.

The problem I think first started about a year ago, after driving for a while I noticed the truck would 'chug' when I came to a stop. It seemed as if it would stall. Acceleration wasnt an issue, just laying off the gas. This problem became worse and worse. It would start doing this after 20 minutes of driving, then 10, then 5. My check engine light never came on and the truck never stalled on me. I parked the truck for about 6 months, came back, put a new battery in it and it started right up, ran for about 5 minutes and then stalled. I started it back up no problem but then died within a few seconds. I started it again, gave it some gas- revved it up to about 4000 rpm and it died again immediately. It didnt sputter, it just died. I can still start the truck, it will still run, but maybe for a few minutes at best. The check engine light still doesnt come on (but it does work when i turn the key)

So Im at a loss to explain this; I have no way of diagnosing the issue and have no clue where to start short of throwing parts at it.

About the Truck
95 GMC 1500, 350 5.7 liter carbeurated. 257000k

Any help is appreciated.
Thanks
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01-23-2014, 01:08 PM
Post: #2
RE: '95 GMC 1500 issue
I'm kind of unclear here. Is it "carbureted" or "throttle body injected?" I'm thinking that a '95 should be Throttle Body which would have an Idle Air Control (IAC) motor. The motor can fail &/or the passage can become carboned up causing that problem. Cleaning the passage with carb. & choke cleaner will sometimes cure the problem.

First, let us know what we are working so we are providing you with the proper information.

Thanks for using the forum,
Garner

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01-23-2014, 01:28 PM (This post was last modified: 01-23-2014 01:37 PM by ScrapHeap.)
Post: #3
RE: '95 GMC 1500 issue
Im pretty sure its carbeurated, its not a vortec.

I tried taking a picture but it was too high quality, so I found one on the internet that is pretty much exactly the same;
Hope that clears things up.

http://imganuncios.mitula.net/92_95_chev...619284.jpg
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01-23-2014, 06:23 PM
Post: #4
RE: '95 GMC 1500 issue
Yeah, this is throttle body for sure so the key here is to read the codes, which means (most likely) replacing the bulb for the check engine light, since you said it didn't work when the key is first turned on.

Now, these days you are not likely to find anyone who has an OBD1 scanner so maybe Garner can post that link on hoe to ready the codes yourself using a paper clip. It's not fool proof but will tell you if a sensor is open or shorted.

Hint, in my experience the most common issue (besides mice filling up the air filter with nesting material) is the coolant temp sensor located near the t-stat housing. If it's gone open circuit then the ECM goes full rich and it will run like it's flooded.
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01-23-2014, 06:35 PM (This post was last modified: 01-23-2014 06:39 PM by ScrapHeap.)
Post: #5
RE: '95 GMC 1500 issue
The check engine light does work, its just not lighting up when the truck dies.
I talked to a mechanic, he seems convinced its the fuel pump (although from my experience, the pump makes an audible sound, a whining before it shits the bed completely) so i sorta doubt its the fuel pump. he does have obd1 for my truck though, not sure how much help it will be though.

Now to address your suspicion with the temp sensor, wouldnt i be able to smell the fuel if its full rich? It does make a lot of sense, especially considering my heater never worked very well. Another thing, if this sensor were to go, it would trigger the check engine light wouldnt it?
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01-23-2014, 08:19 PM
Post: #6
RE: '95 GMC 1500 issue
It may not trigger the CEL unless it's open or shorted but it could be out in left field (reading cold) so the ECM goes rich. This is not the same sender for the dash gauge. This may or may not set a code but the right scanner can read that directly in degrees so a hot engine should be near 190 and a cold engine should be near ambient temp. The heater may be a secondary issue... bad t-stat, low coolant, clogged up, bad heater valve, etc.

As for smelling fuel, it wont be raw fuel but that nasty rich odor and possibly black smoke out the tail pipe. Also black or dark spark plugs if you pull one to inspect.

The CEL should eventually come on with a stalled engine, although it may take 5-10 seconds. It should also come on with the key before starting.

The only way to rule out the fuel pump is to check the pressure both key on and engine running. OTOH, you might want to replace the fuel filter before you go further as it may be starving for fuel and throwing you off course for a good diagnosis.
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01-25-2014, 02:15 PM
Post: #7
RE: '95 GMC 1500 issue
dirty poppet nozzles can cause a no start, hard start, rough idle after start, surge, or other driveability concerns.Under certain conditions, fuel elements may deposit on the poppet balls, seats, or pintles, which can cause the poppet balls to stick in either an open or closed position.there is a tsb issued on this.
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01-25-2014, 02:24 PM
Post: #8
RE: '95 GMC 1500 issue
Thanks for your help, unfortanately checking fuel pressure and inspecting poppet nozzles is beyond my mechanical prowess. I got the truck at a repair shop, ill let you guys know when i know what the issue was.
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