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Thread: FPDM Problem

  1. #1
    Join Date
    Apr 2024

    FPDM Problem

    Good Afternoon,

    Vehicle: 2003 Mercury Marauder - Supercharged

    I have been chasing a gremlin...this is my daily driver, so I am trying to get it running again.

    Problem: No power to fuel pump

    Steps Taken:
    Checked all fuses
    Checked Power at Inertia Switch
    On FPDM
    Checked Continuity between Green/Yellow
    Checked Ground Black
    Checked Green/Yellow for voltage changes, I don't have an oscope
    Checked Light Blue/Orange for voltage changes, I don't have an oscope

    Bypassed the FPDM, Fuel Pump powered up.
    Didn't learn my lesson, bought a Dorman 601-005, didn't fix my problem.

    Brown/White with key on shows 12v
    Brown/White cranking shows 10V

    Seems like it has to be the fuel pump itself, but I am paranoid and am not sure if somewhere in the wire harness there could be more shorts.

    Extra Question:
    When I replaced the fuel pump at the seller's house, I could not get the fuel sending unit out of the vehicle, because one of the plugs was pinched between the body and the tank. We decided that using red butt splice connectors to connect the fuel pump pigtail to the original fuel pump wiring would be fine. Since those butt splice connectors aren't sealed, is fuel conductive? Since I will most likely be replacing the pump again should I cut the pinched connector, so I can solder and heat shrink the pigtail to the original fuel pump wiring?

    I am probably forgetting things at this point that I have already checked.

    Went to purchase this vehicle 2 months ago, vehicle has been sitting for a while, owner showed me recent videos of the car running and driving before I took the 4-hour drive to go get it.
    When I got there, the vehicle would crank but no start, I could not hear the fuel pump.
    While I was there I changed the fuel pump to a Ti Automotive/Walbro GSS342G3, did not have a voltmeter, and the car would not start, I tested the old fuel pump, and it worked on the battery.
    The gentlemen took the vehicle to a mechanic shop that he trusted, which found that the vehicle was not getting ground to the fuel pump and grounded it.
    I came back to purchase the vehicle. There were no more problems that wouldn't allow me to get it home.
    I drove the vehicle home, after the 4 hour trip without a hiccup, I am pulling into a fast food place, the car stalls as I was going 10 MPH. I place it in neutral, and it starts right back up like there wasn't a problem.
    I was getting motion sickness from driving the vehicle home. The fuse was blown for the air suspension, I changed the fuse, assuming the compressor got hot and blew it because the bags wouldn't fill.
    Changed the bags, which was stupid of me, I threw parts at it instead of checking the compressor. The compressor was bad, I changed that.
    I start the car, out of the defog vent on the passenger side I see smoke and smell burning wires.
    I quickly turn the car off, go to pull the air suspension fuse, too late it melted, I was able to get out the fuse, but the fuse holder was already too melted to put a fuse back in.
    Pulled the dash back far enough to find out the blendor actuator was unplugged with it in AC mode, still have to change that. I fixed all the melted wires I could find, dash is still apart. I still have to run a wire to the engine bay fuse box to make the air suspension work again, because it was spliced from the factory behind the dash. To double-check there were nothing else to worry about, I followed down the passenger side of the vehicle to find the ground for the power seat had broken is half from what it looks like and started to corrode, it had melted other wires which I have spliced in new sections.

    Over the next week of driving it, the car randomly stalls, going around corners, getting up to the point that it stalls at 20ish mph twice going onto on-ramps.

    Yesterday, the car stalls and will not restart.

    Thank you everyone for all the posts in this forum and for any help anyone can provide.

  2. #2
    Join Date
    Nov 2009
    Did you say you started it in neutral? I thought there’s supposed to be a neutral lockout. Tech inspection at the race track always checks to make sure that can’t happen. Safety switch?

  3. #3
    Join Date
    Jul 2003
    Yonkers NY
    Should start in Neutral or park.
    03 MM, DBP, Charcoal, 6disk, HS, organizer, spoiler Mods: Z&M arms, Beamtech Led headlight bulbs, LED turns, ditch, tails, reverse & interior(blue), oil deflector, U-Hall Tranny pan. running stock size Cooper Zeon RS3-G1

    02 SL500 Silver Arrow - first aid kit delete, maybe for sale

    08 Town Car Signature Limited, HID's Mods>235/55-17 Z rated BFG G-Force Comp-2 A/S, Addco 1" rear Sway, Posi, Compustar Remote Start, floor liners, trunk organizer, Winter=05 Mustang GT rims, Nokian Hakkapeliitta R-2 235/55-17

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