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Thread: JZX83 shorting issue

  1. #1
    Forum Member 1st year Apprentice
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    Default JZX83 shorting issue

    Hey guys, doing the ol 1J conversion, got the engine in and mechanical side mostly done (minus IC piping, exhaust etc) partially wired a manual x81 ecu using the usual guides, just to start it and check the health of things.
    Went to turn the key and got no power on ACC or on or anything, had a check of the wiring at the ECU and it seemed fine.
    Battery was some old thing with hardly any power so went to put a jump pack on it and it sparked at me indicating a short, went to town checking things, alternator wiring lengthening was fine (unplugged with no difference) grounds were fine to my knowledge (battery, chassis and block) however no ground on the trans as its a temporary a340 (does this matter?)
    Same deal with the ECU, unplugged with no difference. Then had a (domestic) sparky mate over who had a look at it, he determined it was a full short which we began to chase for a good couple of hours, eventually took all fuses out from interior and engine bay (all of which were in tact) and his multimeter was still indicating a full short.
    I had hardly touched any wiring in the car, and it was running with full electronics when the 7M was in it, just the usual 7M-1J stuff. I'm lost for ideas and not too savvy with wiring so I have no idea what it could be, just wondering if anyone has any ideas? Areas to check etc? Thanks.

  2. #2
    Junior Member Automotive Encyclopaedia
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    Default Re: JZX83 shorting issue

    I would unplug / undo the Alternator & startor motor main power wires & see how you go from there, i pressume the battery post is where the fused main feeds for the ignition etc is taken off from ? & also take off / undo the fused main feeds / wire to the car electrics from the battery post to, but do it all in stages so you can see what hopefully works..

    I pressume you have triple checked both batteries are being connected correctly, also take the old battery out because if its really dead flat they sometimes draw quite a current initially when you connect up a good battery to them, which will cause a spark ..

    Is the replacement battery a good known source one, i remember hearing years ago of a guy charging up a dead dead flat battery with the polarity of the charger reversed so the Negative terminal of the battery then became the positive & visa versa once the battery was charged up, i didnt see it in person though so you never know, maybe it was just a good story ???? ..
    Last edited by lexsmaz; 30-11-2012 at 12:22 AM.

  3. #3
    Junior Member Automotive Encyclopaedia
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    Default Re: JZX83 shorting issue

    maybe u put the battery positive cable which goes to starter solenoid to the block as a ground
    but this would spark big time
    is it sparking slightly or alot

    disconnect the 2 or 3 wires on battery positive and touch one at a time and find which one is sparking
    either the starter cable one or the fusable link one

    i always have issues with domestic auto electricians hehehehe

  4. #4
    Forum Member 1st year Apprentice
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    Default Re: JZX83 shorting issue

    Yeah problem is the line that goes to the fusebox, the only other positive that comes straight off the battery is the starter motor and that is without a doubt attached to the starter. I disconnected that and anything else to eliminate anything, and still had nothing, the short is before the fusebox as all the fuses were unplugged and instead of an open circuit, I still got a short.

    Battery should be ok. It was removed from this car as a decent runner. We tested for a circuit using a multimeter (some technique I didnt quite understand)

    I'll do that lexmas, I may just end up tracing wires which I really didnt want to do.

  5. #5
    Forum Member 1st year Apprentice
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    Default Re: JZX83 shorting issue

    Solved.
    Starter was the problem, using an older 7M starter (that did work just a month before) the positive post/screw must have taken a hit or something, whenever the battery positive touched it it was fine but as soon as it was tightened with the bolt it must have pulled the positive away from the motor and shorted somehow.
    Finally found my 1J starter and tested it with no problems, put it in the car and it started raining but its all good now.
    Thanks guys.

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