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  1. #1

    Default 84 GT350 Turbo EEC Diagnostics

    I believe my PCM is bad and warrants replacing. I would appreciate anyone's opinions or guidance.

    Car will not prime fuel pumps and no 12V to the injectors.

    Tank, fuel filter, and two pumps are new
    EEC Relay and Fuel Relay are new

    There is 12v, key on, at the orange wire at the fuel relay and I can jump the orange and pink/black wires to get the pumps to run. All other fuel relay electrical points read 0v.

    If i try to jump the fuel pumps with the ALDL port, the pumps do not turn on.

    I have used a voltmeter to check all fuseable links I can find and all check out.

  2. #2
    FEP Super Member xctasy's Avatar
    Join Date
    Jun 2012
    Dunedin 9011, New Zealand, South Pacific


    The EECIV has a four earth baseline voltage system. Wiring to and from the pump is the likely problem. It was sub optimal from birth, and although a pest to check, that's gotta be your first thing.

    Unlike earlier EECIII's, EECIV takes a sub 12 volts reference signals on nearly all systems, and polls the values as Analogue to Digital conversion, which then triggers DTC fault codes thru the six pin plug.

    The operation of critical systems stops if voltage history is out of range. To scupper the EECIV operation, just a few voltages have to be out of range to raise a fault, and then a shut down. Shut downs are wiring faults, like O2 sensor mis wires, or neutral saftey switches, or some major issue.

    Most of the time, a visual check of the capacitors and a recheck of the 60 pin plug will get it back into operation. Normal code reading is an important first step.

    Probing the wires to the pump, and making sure the inertial switch hasn't been thumbed out of operation are first steps.

    Haystack has a reference to Joel's corralnet basic EECIV checks. They are good ones. jrichker at Stangnet has some too.

    Doing the KOEO (Key On Engine Off) will hopefully show a fuel pump related code.

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