Engine starts right up but will not run on my 3500 8.1L.

Discussion in 'General Chevy & GM Tech Questions' started by thenorthpohle, Dec 22, 2010.

  1. thenorthpohle

    thenorthpohle New Member

    I made the mistake of leaving something on in the cab of my 3500 8.1 Liter engine and the battery ran down. I charged the battery, but now the truck will start, but only runs for about 3 seconds, then shuts down. I put an analyzer on it and it give me a P0068 message about the MAF and MAP sensor and the throttle position, etc. I changed the MAF and the MAP, but still get an error code. It almost seems to be fuel pump issue, although I can hear the fuel pump turn on, I tried to put some gas into the air intake and it does run a little longer, also the fuel pressure seems to be low, as it does not spurt out vigorously, when I checked the pressure. It seems like gas should shoot out if it has 60 pounds of pressure. Do I need a new fuel pump?

    I am at a loss, any help would be very much appreciated. Do I need to reset the PCM . . . after replacing the MAF and MAP? Not sure what to do at this point, I can't seem to locate any vacuum tubes that are broken or cracked.
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    You need to check the pressure with an actual fuel pressure guage. And if the fault is repaired then the truck should start just fine with out resetting the PCM.. SO get a good reading on the fuel pressure and go from there.
  3. thenorthpohle

    thenorthpohle New Member

    I checked the gas pressure it is as 60 lbs with a fuel gauge, I just checked it on the rail on the right side looking at the engine from the front, is that the only place to check it? In any case seems like there is enough fuel & pressure. And I would not think it would die so consistantly, about 3 seconds after starting, you can time it, seems like something electronic. Any other thoughts?
  4. Taddpole

    Taddpole Member

    Have you checked the fuel pump relay? Or the fuel pump module? I think the fuel pump module holds the fuel pump on for the first few seconds and the fuel pump relay takes over after that (I could have this backwards). You did'nt give the year of your truck, on my 1990 2500 the fuel pump module is clipped to the ecm behind & to the right of the glove box( pull the glove box liner). The fuel pump relay is under the hood, the location depends on the year of the truck. This is the first time I have posted on the forum, so I hope this helps you.
  5. stephan

    stephan Rockstar 4 Years 5000 Posts

    Welcome to the GM truck club Northpohle. You too Taddpole.

    Northpohle, when you are watching your fuel pressure guage, & the engine dies, does your fuel pressure drop before the engine dies? From what you say in your post, you do not indicate that it does...

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