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Thread: Why would my fuel pump have been wired this way?

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    Why would my fuel pump have been wired this way?

    So I have the feeling something is broken somewhere based on how the fuel pump in this TT is wired (not my doing).

    There is a small wire spliced into the black/blue wire at the fuel pump (power) that is run all the up under the dash and was jammed into the socket for the main engine fuse in the fuse box near the driver's knee. Apparently this is how the pump is being powered and controlled.....they even put in a higher amp fuse (25) to combat the extra load I guess...

    So, with this wire disconnected the car will not start. The pump does not appear to be getting power. The black/blue wire is not severed at the pump, it's still wired normally, so if it's not getting power then what's the next culprit? I suppose that wire could have a break in it, but what other relays and switches do I need to be looking for? The fuel pump relay near the MAF? This couldn't have anything to do with the MFI relay could it? Do I need to be listening for that thing to tick or not (is tick good or bad?).

    The car is also run by an AEM EMS, they don't have to be wired up or configured specially for the fuel pump to get cut on do they? lol

    Any help would be appreciated. One day I'll sort all the mistakes made the previous owner, lol

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    Better than that "other" place Not Verified Feedback Score 2 (100%) x2xtreme360's Avatar
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    The system is pretty simple actually, so diagnosing shouldn't be hard.

    The MFI relay supplies power to the fuel pump relay down by the MAF. The pump either receives full voltage from the battery, or the relay changes the circuit to flow through the resistor, and then to the pump.

    I would, first and foremost, use an ohmmeter to check for breaks between the fp relay and the fp. If that appears to be OK, check for a break between the MFI and fp relay.

    The previous owner just ran a power feed from the IG Switched engine fuse, so it would be powered up when the car is keyed on. It's a really bad way to fix a problem

    Another easy way to check for a break would be to use the test port over by the passenger side strut tower. It's black and it has a cap on it. Jump the positive battery terminal to that connector and listen for the fuel pump.
    Last edited by x2xtreme360; 04-25-2011 at 10:13 PM.

    Vacuum reduction, Powdercoated misc, cruise relocate, Evo9 BOV, Custom catch cans, Russell fuel filter, SS braided fuel lines, High flow fuel loop, Autogage fuel gauge, Catless DP, DNP Y-pipe, Fuel pump hotwire.

  3. #3
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    Hey Steph, it might be something like on my Stealth.

    One day I randomly just lost power to the fuel pump. I traced, diagnosed, tracked, looked, poked and prodded and couldn't find any breaks. I had power to the MFI, but not to the pump. I ended up attaching a wire to the black/blue wire at the MFI and ran it under the carpet to the black/blue wire at the fuel pump connector to make it run like stock.

    [06-05, 19:29] OhioSpyderman: Brian, finding a woman is NOT the answer, you need to shop for a good VACUUM

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    My fuel pump relay appears corroded beyond belief, so I'm going to go with that as the culprit for the time being lol. I'll just remove that guy and jumper it as if doing the resistor bypass. It shouldn't really matter either way (bypass or not) as long as it functions since I'm doing a proper hotwire at the same time, right?

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