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Thread: I hot-wired my car... Looking for help

  1. #1
    Join Date
    Sep 2007
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    Houston, Tx
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    1,978
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    '78 320i

    I hot-wired my car... Looking for help

    edit: I think this one is going to be too much trouble to diagnose over the internet, so Im going to just fine tooth comb what I went over and look for shorts. I would bet the farm on something under the dash but who knows.



    To get some basics out of the way... swapping a 1991 M42 in to my 78 320i. The battery has also been relocated to the trunk. The car had a toooooonn of wires tapped in to ignition over the years from various PO, I've been capping them off this project. The car cranked last week and ran but it had a slow battery drain so I keep it removed. I assumed there was a short due to the hackjob wiring.

    Initially, I had the fusebox wire connected right to the starter, when it last ran, but I since moved it to the junction box. I also capped off 3 wires that were tied to the green, black and violet ignition wires. Not sure what they were used for, outside of the radio.

    I tried to crank her up last night and as soon as I touched the battery wire to the terminal, it started to crank. So I'm taking a few steps back to rectify wiring and make sure I have everything set up.


    A few more notes, I checked the 4 wires (bl/yl, bl/gn, bl and the wire to the junction box) at the starter for any shorts and it all looks good and as it should be. Outside of capping leach ignition wires and moving the fusebox power, I cant think of anything else that changed since it last started.
    Last edited by jaredmac11; 06-16-2018 at 10:24 PM.

  2. #2
    Join Date
    Sep 2007
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    Houston, Tx
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    '78 320i
    My first theory was I goofed something up under the fuse box, so I just removed the power to the fusebox but I still have a short.

    However, it looks like the 2.5 gauge bl/yl wire off the starter to pin 18 of c101 is the source of the issue. If I remove this wire, I dont have a short and no issues. So it seems to me that there's a short under the dash at the ignition.

    Side note, I think I have excessive wiring on my starter. The E30 has a small bl/gn wire that goes to pin 15 of the C101 and then to the unloader relay. However, the E21 shares pin 10 of the C20h for the unloader relay and the starter, which I already have wired. I can remove this bl/gn wire from the starter correct? It's already terminated in the harness but connected to the starter.
    e30 m42:
    starter to unloader.JPG

    78 e21:
    e21 starter to unloader.JPG


    The unloader relay is only meant to cut power to all auxiliary items while the car is in start so its likely a separate item from this issue, correct?


    Second Q... I noted there is no start relay... did anyone ever implement this in their wiring? Or is this handled separately? It's in the automatic versions of the car only.
    Last edited by jaredmac11; 06-17-2018 at 05:14 PM.

  3. #3
    Join Date
    Feb 2016
    Location
    Sacramento, CA
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    1,077
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    1979 E21 320i
    Knee jerk reaction is that maybe one of the wires you cut off the ignition was a previous owner's fix for a broken wire. Maybe try reconnecting them one at a time?
    -John

  4. #4
    Join Date
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    '78 320i
    They were just dangling, unconnected initially. Im going to take time to fine-tooth comb under the dash and confirm your suspicions. There are some wries that are literally just tied in to an existing wire. No crimp, no solder... just tied in (non ignition wires). The 2 wires tapped in to ignition are after the ignition connector and are crimped in, so I capped them off.

    I may have to unbundle the fusebox wiring and start taking a look one piece at a time.

  5. #5
    Join Date
    Sep 2007
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    Houston, Tx
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    '78 320i
    It was the unloader relay. Had to wire the car back to stock which took some time, but it wasnt really necessary. Wish I thought to change the unloader relay earlier.

    Car runs like crap, so on to the next series of issues....

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