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Thread: Fuel Pump Problem-- NEED HELP!!!

  1. #1
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    Fuel Pump Problem-- NEED HELP!!!

    I own a 1987 Chevy C10 Pickup with a Holley Throttle Body, 2WD, Fuel injection. The fuel pump stopped working on me and truck died. Replaced pump, and it is still not starting. Checked volts going back to fuel pump and it's showing it's only getting 6 volts, instead of 12 volts. Not sure what the problem is??! Can anyone give me advice or refer me to a wiring diagram so that I can check to see if it is the wiring or a bad relay or what?! Any advice would be greatly appreciated, im desperate!!

  2. #2
    Senior Moderator chevychase's Avatar
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    Check connections good are you getting a good ground? Here is a diagram where are you checking power at will be tan and white wire or orange at fuel relay.

    Gitter done have fun. Running on empty...running blind...running behind.....

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    Grounds are good...found the relay.. what next? How do i determine if its a bad relay or not?

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    Senior Moderator chevychase's Avatar
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    Can put 12 volts to orange wire . or put 12 volts to terminal g here check see if getting power to the fuse 12volts.
    Could be either relay ..bad wire ...corroded or bad fuse..ignition switch...bad ecm ..oil sending unit or real low on oil .
    First thing to check run 12 volts to g terminal see if pump comes on if not a bad wire connection to pump or at pump.

    Gitter done have fun. Running on empty...running blind...running behind.....

  5. #5
    Senior Moderator chevychase's Avatar
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    You bypass all when jumping terminal g ..relay ..ecm ..all

    That would be b2 on wiring diagram terminal g

    Gitter done have fun. Running on empty...running blind...running behind.....

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    Thanks for the tips and diagrams!! gonna have to check those things tomorrow...rain got me shut down! appreciate it man!! Ill get back on here with feedback!! I'm definitely a better carpenter than a mechanic lol

  7. #7
    Senior Member 87c10slammer's Avatar
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    check your ecu fuse. had the same problem in my 87.

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    Senior Moderator chevychase's Avatar
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    Quote Originally Posted by 87c10slammer View Post
    check your ecu fuse. had the same problem in my 87.
    Will be the cigarette lighter fuse.

    Gitter done have fun. Running on empty...running blind...running behind.....

  9. #9
    Senior Moderator chevychase's Avatar
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    When you check for power at pump or relay will only have a few seconds . Ecm will send power to relay via the green and white wire at relay.
    Turn key to on do not have to crank on engine. If you get power at green and white check for power at orange wire .
    If you get power at orange wire check for power at fuse . Circuit goes ecm..relay..fuse..then pump.
    When you turn key to on will have few seconds to check..will have to turn off key for 5 seconds try again .there is a small delay.
    Can you hear relay click when key turned on? This truck does not have security does it? Check the black and white wire for good ground off the relay.
    Check the bulk head connector good connection and clean.

    Gitter done have fun. Running on empty...running blind...running behind.....

  10. #10
    Forum Moderator Boudin's Avatar
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    Relays can be tricky to check because they will work a lot of the time when testing them because they are only bad when hot sometimes. Pull the relay. Take the positive and negative wires from a 12 volt source (battery works well) and put it to the two pins that are parallel to each other. You should hear a definite click in your hand as you hold it.

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