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Thread: fuel pump not working

  1. #1
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    fuel pump not working

    1999 GMC Sierra 4x4 5.3L 1500 ...i just installed a new fuel pump 4months ago, 2 nights ago i was leaving work and my truck just died on me. i noticed the fuel pump wasnt running so i suspected the pump went bad again, exchanged it underwarrenty for a new one, and still doesnt work. then i checked and it isnt getting any voltage to the pump, it is getting volts to the sending unit. i swapped the fuel pump relay out with the horn relay and still did not work and didnt get any volts at the pump. all the fuse are good , i checked cont. in all of them with a volt meter. There is a prime slot in the fuse box under the hood where the FP relay is at and you can put a wire to it and a hot terminal and the pump work and it will start up and run as long as you have that wire in the prime slot. so the pump does work. any suggestion would be greatly appriciated

  2. #2
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    do a fuel pressure test

  3. #3
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    thanks , but i know the a fuel pressure test will come back with no pressure since the fuel pump is not running

  4. #4
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    If it comes back with nothing then your having trouble with defective fuel pumps. Maybe better off to spend the extra cash to get one from napa or carquest.

  5. #5
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    its not getting voltage to the pump, the pump works , like i said in my post if you stick a wire in the prime slot on the fuse box , the pump will run, and the truck will run. oh and both pumps were brand new delphi fuel pumps from oreilly auto parts

  6. #6
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    check for poor fuel pump ground

  7. #7
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    well thats what im thinking , but i have no idea where to check for the ground at, the ground wire runs into a wiring harness and up to the front somewhere amongst all the other 10,000 wires. lol.. also , can the ignition have something bad in it that prevents power to go the fuel pump?

  8. #8
    Senior Member outdoors1988's Avatar
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    Quote Originally Posted by yzrider647 View Post
    well thats what im thinking , but i have no idea where to check for the ground at, the ground wire runs into a wiring harness and up to the front somewhere amongst all the other 10,000 wires. lol.. also , can the ignition have something bad in it that prevents power to go the fuel pump?
    The ground on mine is bolted to the fram by the tank but have to drop the tank to see it but i have a 1989 gmc suburban might be the same but idk just trying to help

  9. #9
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    Its not a ground issue if the pump will run. Check to see if you have voltage at the relay.
    Joe
    89 K2500 Chevy, Wee-Oh-five 294K miles
    1962 Scout 80 parts I guess
    1966 Scout 800 resto job
    2005 Chevy 2500HD Short cab long box DURAMAX
    1996 P30, 6.5 NA Mac Mobile
    whole lot of buicks

  10. #10
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    there are 4 prongs on the relay , it shows voltage when i put my mutimeter on the left prong closest to the fender and the right one closest to the engine..... is it suppose to show voltage there? and i checked the grounds just to make sure , there are two ground wires that come out of that wiring harness and bolt to the frame underneath the front of the drivers side door, i cleaned them off real good and put them back , still didnt work...

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