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  1. #1

    Cool 1994 GMC Suburban : Running Issues

    I have a 1994 GMC Suburban 2500 with a 5.7 ltr TBI fuel system. It has 211,000 miles on it. The truck takes too long to start. Once it does it runs fairly well but lacks good pickup. In wet weather it starts real hard, and runs ragged. I replaced the cap , and roter. Wires were replace 2 years ago. It tends to idle too slow an stall a lot. I am thinking it may be a fuel pump but it does make a noise when the key is turned on .... Any ideas? .... Thanks, Dave

  2. #2
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    Have you ever done a rebuild on the TBI?? (includes a new fuel pressure regulator) If not that would be one way to go since even if the pump is running if the FPR isnt doing its job then the motor will run like you are describing.
    Mike

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  3. #3

    Default TBI Rebuild

    Hi , Thanks for the response. Since it does not seem to hold fuel pressure I was thinking the same thing. I will have to get a fuel line T and put a fuel pressure gauge on it. It does not have a shradder valve . Thanks for the tip I will let you know ...

    ---------- Post added at 09:10 AM ---------- Previous post was at 09:07 AM ----------

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    TBI Rebuild

    Hi , Thanks for the response. Since it does not seem to hold fuel pressure I was thinking the same thing. I will have to get a fuel line T and put a fuel pressure gauge on it. It does not have a shradder valve . Thanks for the tip I will let you know ...

  4. #4
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    You need to have at least 13 PSI from the pump and it should hold that pressure pretty well.

  5. #5

    Default Fuel pessure checker

    So , I think it comes down to the fuel pump or the fuel pressure regulator. The truck starts quickly when starting fluid is sprayed. Slowly without it no mater how long I sit with the key on. The book says 10 lbs. There is no return line to the tank. Do you have any resolutions to being able to check the pressure. There is no schradder valve and I can't find anyone with a T valve to put in between the gas line and the TBI unit. Do I have to fabricate one ?

  6. #6
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    You need to get a Tvalve that goes inbetween the Fuel Filter and the line coming from the tank. And i would lean twards it being the FPR if you havent ever had to change it since they do wear out over time.

  7. #7

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    OK , So I fabricated a t for the fuel pressure guage in place of the fuel filter. Key on , no pump sound , no pressure reading , a dribble when you hold down the pressure relief button on the pressure guage. Start the truck ( hard starting) and you get a 6 or 8 lb reading on the pressure guage while it is running. I know this vehicle automatically dumps the pressure when you turn off the truck but that is with the key off . SOOOOO I assume the 0 reading with the key on and motor not started is bad.. My question would be is the pressure regulator bad or is the pump bad .... From the books I can not tell how to determine that. Any ideas ....

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