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Thread: Fuel pump not working/wiring?

  1. #1
    Senior Member malk234's Avatar
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    Default Fuel pump not working/wiring?


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    I have an ADM AE86 converted to 4AGE by previous owners mechanic.

    Just recently after about 5 months of driving and two years of ownership, once it warms up and I switch the car off, it isnt able to start until the engine is cooled down to about 20-30 degrees.
    There is no fuel pressure/no fuel being delivered.

    I have been looking at the wiring and there is a blue/white wire leading from the fuel pump, under the car, to a single bullet-like fuse in the engine bay, through the firewall with the rest of the wires, to a relay attached by a bracket to the ecu.
    I have read up about the green/red wire that is connected to the relay which activates the relay for the fuel pump.
    From what I can see/test, the problem seems to be in the bullet-like fuse. The fuse is 20A and although it seems to not be broken, I don't believe it is carrying any current.
    Though, I wouldn't be surprised if something was wired up incorrectly.
    The fuel pump works and I have tested that there is no current at the connectors near the fuel pump when the car wont run.

    My questions are:
    Would it be common for a fuse to burn/snap under that load and return to previous static position once cooler? (do I need a larger/different type fuse?)
    Are all the wires in the correct places? (see photos (I have looked at all the wiring diagrams, I just want some people with some experience to check over))
    Is there any information I am missing?

    Cheers
    Todd





    If you havn't broken it yet, your not driving hard enough

  • #2
    Senior Member malk234's Avatar
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    And for those wondering, yes I do plan to rewire the whole thing.
    If you havn't broken it yet, your not driving hard enough

  • #3
    Senior Member malk234's Avatar
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    Also with the photo of the fuse, I had to rewire another fuse in there (which worked for three starts).
    Hence the blue/yellow wiring.
    If you havn't broken it yet, your not driving hard enough

  • #4
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    Where is your fuel pump located??? Not in the engine bay is it? There is no good reason to run that blue wire into the bay otherwise. By the looks of it they have cut into where the diag box sits and ran it back from there..

    Looking at your ecu wires, one of the power inputs looks it could be loose, it might just be the type of connector that has been used though but this wouldn't help your problem. Check it either way.

    With the picture of the relay

    You should have power when the ignition is on to the middle pin black / red wire. The white / black one should be hooked into a permanent solid earth. If the Black / Red wires is fused in factory configuration there is no fuse on the blue wire. The difficult thing in troubleshooting this is the ecu detects the engine isn't running then switches the green /red wire away from earth, hence taking power away from the fuel pump.

    If you are stuck on the side of the road and powering the fuel pump is the problem, check by disconnecting your ecu plug and earthing out the green / red wire directly and measure the power at the pump or listen for it if it is loud enough. To get the fuel pump running join the middle back / red wires to the blue one to get you home.

    Run a diagnostic check to grab any codes for peace of mind too.

    EDIT: When cranking the fuel pump should run, which is done by applying power to the thicker of the two wires on the edge.

    Pinouts / Factory Colours.
    Switched Earth (ecu/afm) - Green / Red
    Switched 12v (starter) - Black / White
    Output (Fuel Pump) - Blue / black
    High Amp Input (Output of EFI relay) - Black / Red
    Non Switched Earth - White / Black

    Last edited by Matt; 25th July 2012 at 10:48 AM. Reason: Wrong info misread problem

  • #5
    Senior Member malk234's Avatar
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    Hmm ok.. the black/white wire from the relay becomes a brown wire and goes with all the other wires up to the engine bay.. havent traced it any further yet.

    With the black/white wire underneath the green/red wire in the ECU, where is that meant to go?
    As it is just left hanging connected to nothing..

    If you havn't broken it yet, your not driving hard enough

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    That black/white wire that is taped up can be ignored as it is the A/C pin on the ecu...

    If the black/white wire joins up with the brown wires itd be earthed to the inlet manifold along with the other wires. Check the black/white wire has power when cranking, don't confuse this with the white/black earth wire

    The fuel pump by the sounds of it isn't running when you are cranking the car...

  • #7
    Senior Member malk234's Avatar
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    Nope, it isn't !

    I dont know how it has been starting in the past and the other morning for three times in a row..
    Last edited by malk234; 26th July 2012 at 11:25 AM.
    If you havn't broken it yet, your not driving hard enough

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    Left over fuel/pressure in the rail. In a nut shell, trace the plug on the starter motor and splice in the thick black wire on the fuel circuit relay. If you get stuck, shoot me a pm and i'll talk you through it.

    And your wiring isn't as bad as some of them that i've seen. A quick test form a quick jumper between the black / red wire and the black/white (could be plain black) wire (bottom right corner of your pic) and see if your fuel pump runs and try starting it.

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    Senior Member malk234's Avatar
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    Okay, so the fuel pump works when it is cold but it doesnt run once it has warmed up.. any ideas?
    If you havn't broken it yet, your not driving hard enough

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    So the car will be running and then suddenly die?

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