No power to fuel pump inertia switch, 91 MTX

Discussion in 'Gen 1 & 2 - Electronics & Audio' started by tompumped, Sep 15, 2020 at 9:18 PM.

  1. tompumped

    tompumped SHO Member

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    I haven't had time to find wiring diagrams. I have a lot going on right now and I could really use the help or guidance.
    This is my first 91 and the wiring is different than the three 92s i've owned. Full disclosure I just got done installing a different motor with the same original complete engine harness. I did a 3g alternator upgrade using the factory alternator charging wire harness from a '95. I was able to use the yellow/white wire with 20ga fusible link from the 95 alternator charge wire harness and solder that to the original yellow/white wire over by the starter solenoid. I completely eliminated the original charge wire, and the yellow/white wire with fusible link that was attached to it. I also did a gen 2 starter upgrade. It will crank, the S terminal for the starter is part of that 95 alternator harness.

    I can not get power to the fuel pump. If I put power to the pump at the intertia switch it primes. The CCRM is coming on and sounds as it should. Turning on for a few seconds then the fuel pump relay kicks off. This 91 also has a yellow wire with 20ga fusible link that is directly attached to the positive battery terminal. The CCRM will not activate without that wire connected.

    The brown wire that you connect to the ECM test terminal to get the CEL to flash to count codes should be a ground IIRC but when I check for continuity or use my power probe it isn't.

    When I have more time I will see if I can get the fuel pump to activate from that ECM test plug, but I need to find a pinout of it. I will also double check the voltage readings at that plug, but I think I had low voltage there. The ground is connected to the back of the intake, the ground that is part of the harness for the ecm test plugs is also connected.

    I have no clue what i'm missing or what I did wrong. It's not the ecm/ccrm, I have known good spares. Thank you in advance.
     
  2. zoomlater

    zoomlater SHO Member Supporting Member

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    tompumped likes this.
  3. tompumped

    tompumped SHO Member

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    Thanks. I didn't even think that I could probably use the prints I have from 92 because they have the same CCRM. I have blueprint size wiring diagrams that were included as a surprise when I bought a factory service manual years back.

    The car ran, I only put this engine in because it has new heads, bearings and gaskets. I'm missing something or I did something wrong when I upgraded the starter/alternator I just figured there had to be someone on here that has the system memorized practically down to the color of the wires. I thought maybe just by my explanation they'd know. I've dropped subframes and engines three times before this, but I screwed up this time.

    This is the nicest SHO i've ever purchased I hope I can stay calm enough to figure it out. I'm working insane hours and I can't deal with any more problems right now. I was completely disgusted with this and somehow I managed to screw up the timing for the first time in my life on any motor i've ever worked on. I have 70 psi on cylinder 1 and zero on 2. I hope it's just the exhaust cams out of time. I timed the engine a year ago and I don't remember what I did.
     

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