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No start M20B25 swap into 2002

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    No start M20B25 swap into 2002

    Hi everyone, I have an M20 out of an 87 325i that I transplanted into my 73 2002. The M20B25 wiring harness is integrated into the car and I have confirmed (using jlevie's excellent no-start guide as well as bavauto's) that everything was working fine prior to my car going in for exhaust work. By everything I mean I had spark, engine turned over. Signals and grounds to/from DME all checked out.

    Got the car back from the exhaust shop, re-installed the batt and at first it fired once then completely died. Subsequent efforts to start the car failed.

    When I turn the key (START), I do not hear anything coming from the starter. No solenoid click. No turning. I do however see a spark between the back of the starter housing (bell housing) and the firewall. For those that may not be familiar with the swap, the transmission is about an 1/8' or so from the firewall. Maybe there's a short in the solenoid itself. My grounds are good though, so I'm confused.

    Anyway.

    Checked all my grounds and they are good (Oil pan to body, batt to body, the group of grounds on the main engine harness).

    Per my bentley manual, it says you are suppose to have at least 8 volts at terminal 50 on the solenoid and at least 8 volts on the field-winding strap.
    I have over 11 volts on terminal 50 (coming from ignition switch) but only 7.4 on the field winding strap.

    Bentley says to replace the solenoid in this case.

    Does this sound like a reasonable diagnostic? I don't know what would have happened during the time it was at the shop. All I can think of is perhaps I wore the starter out when I tried getting this car to fire for the first time prior to getting the exhaust. But like I said, it fired once before going silent.

    Just so I can get some peace of mind, I have attached a picture of my starter wiring for reference.

    The three wires on the largest stud (on the bottom - image is rotated 90 degrees clockwise) are:
    1. +12v from batt cable(junction)
    2. original 2002 accessory harness
    3. Alternator

    The wire on the left (black/yellow) is the starter signal (terminal 50?)


    Click image for larger version

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    TIA
    C

    #2
    the spark to the firewall concerns me a little

    easy test: put some kind of insulating material between the starter and the firewall and see if that changes anything
    past:
    1989 325is (learner shitbox)
    1986 325e (turbo dorito)
    1991 318ic (5-lug ITB)
    current:
    1985 323i baur (project to resume soon...)
    2013 ninja 300 (way more fun than a car)

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      #3
      Originally posted by decay View Post
      the spark to the firewall concerns me a little

      easy test: put some kind of insulating material between the starter and the firewall and see if that changes anything

      Solved the problem. My engine grounding point on the body wasn't good. Had one end of the grounding strap attached to the frame rail which showed really high impedance. Moved it to another location and voila, car started.

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