Question about 2005 Pontiac Grand Prix

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Fuel Pump Not Getting Power

Is there an emergency fuel cut off switch on a 3800 series III? I can hot wire the pump from the relay and get the pump to start when turning the key, but it will not start without the hot wire.

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  • 3 more comments 
  • 06GP3800 May 28, 2009

    no...I just tested the system and found power up front, but not in back. I just tried other forums and now signed up for this one. Thanks for the info. It looks like I have quite a bit of wire to run.

  • 06GP3800 May 28, 2009

    I was out testing the whole system and found that after I finally got it running the relay loses the relay signal voltage. I can get it to run for 2-3 hours then nothing. I am wondering what could make the PCM shut down that voltage when hot. I am not getting an error code.

  • 06GP3800 Apr 28, 2010

    It turned out that the wire harness was rubbing the engine and was shorting.

  • yadayada
    yadayada May 11, 2010

    are u talking about when the key is on but the engine is not running? if this is the case the PCM shuts off the fuel pump circuit after a few seconds.does your car have an oil pressure fuel pump switch, this my be the problem

  • yadayada
    yadayada May 11, 2010

    GM does not use a fuel pump cut off switch, didn't u ask this once before??



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If you are jumping power from the leg of the relay that energizes the pump, first check where the wire enters the connector to the relay. if that is good, I would just run the jumper wire to the pump permanently and use it. only other option would be to trace the wire from the relay to the pump and find out where the disconnect is. If you check your diagram and find that nothing else is connected downstream of the relay it is Ok to do. I would also cut the wire right at the relay to prevent any future shorting from developing.

Posted on May 28, 2009


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