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Battery Died: Now My M20B25 Won't Idle?

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    Battery Died: Now My M20B25 Won't Idle?

    The car sat exactly 3 days, but I was starting it everyday with no problems. Then the next day, I wanted to use it but the battery was suddenly dead. It didn't even crank.

    So I proceeded to use a jumper cable and it started in one click. The weird thing though was this: Everytime I took out the cables, the RPM would slowly go down to a sputter and die. The second time I jumped it, I jammed something onto the accelerator to let it rev, but the same thing happened. Repeated it 2 more times, and the same thing happened, so I gave up.

    The reason why its sitting is because I removed the cluster for repairs. (Yes, it starts without the cluster. It runs too).

    Other observations: Temp is only moving to 1/4 instead of near 1/2, and sometimes has a nervous tick, and I'm suspecting that its the Coolant Temperature Sensor.

    Any ideas, please? TIA!

    #2
    Could be several things. If the ECU memory was wiped, it will take driving for 50-75miles to re-learn.

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      #3
      Thanks, but I don't think it will just sputter and die. I've worked on the car before and needed to take out the negative connection many times. Yes, the ECU has to re-learn but it will still idle. This one, even with a high RPM, will die when I take out the connection from the jumper battery source.

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        #4
        Early or late model? If early then the alternator exciter is in the cluster I believe. It would Cause the battery not to charge if the cluster is out.

        -NICK

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          #5
          Its a late model, '88, so I'm not sure that it applies? Thanks.

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            #6
            Along that line of thought, maybe your alternator is dead? See if you can run a voltmeter across it while it idles. It should be around 14v I think. Any lower than 12v and you've got a problem.

            Could be the alternator voltage regulator or the whole alternator.

            How old is the battery? They are maintenance items.

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              #7
              Sounds like alternator. Jump it, then remove jumper while on. Your batt and alt is wiped out


              Sent from my iPhone using Tapatalk

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                #8
                Without the cluster in place, the alternator will not charge resulting in starting but not running.
                Owner - Bavarian Restoration
                BMW and European Electronics Repair and Restoration
                www.BavRest.com
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                  #9
                  Thanks, Greg!

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