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still having random no power to the MS issues

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    still having random no power to the MS issues

    the car will randomly not power up the ecu after driving and then randomly start working (not for long) after sitting. i can't seem to develop a pattern to chase the issue down. NOTE i have had 7 different main power relays the first 2 were known good used the rest were new all factory bmw and 1 bosch.

    using this diagram to check the pin outs on the harness at the ecu (with it disconnected and key on and off as follows:
    link to diagram http://www.megasquirt.325ix.com/MS_t..._motronic.html

    with the ecu disconnected and the key on it reads as follows:
    #2 no ground
    #3 ground, but no buzz (indicating a weak ground)
    #14 has no pin
    #19 ground with key on
    #24 ground with key on
    #36 reads (+) should be ground and reads the same key on or off
    #37 reads (-) with no buzz key on or off

    at the main relay:

    key on:
    #30 (-)
    #85 (-)
    #86 (-)
    #87 inside nothing
    #87 outside nothing

    key off:
    #30 (+)
    #85 (+)
    #86 (+)
    #87 inside (-)
    #87 outside (-)

    sometimes the main relay will rapidly click, but again without any pattern, just sometimes.

    ALSO: i have run the MS seperate from the car on the stim with the laptop and let it run for 4 hours cycling it off and on with the toggle switch 50+ times and everything seems to be working correctly with it on the stim.
    Last edited by der affe; 05-29-2012, 12:43 AM.
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    #2
    I'm starting to wonder if the relay trigger could be the cause. maybe try what we discussed earlier, reconnect that jumper you found, and ground pin 85 of the main relay.
    Build thread

    Bimmerlabs

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      #3
      so do this inside the MS correct?

      i was getting ready to solder the jumper wire to the wire on the bottom of the connector where the wire is exposed.

      should i wait and rewire the ms first?

      i am going to borrow a power probe 3 tomarrow so i can see what the actual voltages i am getting are also, incase there is a low voltage issue there too.
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        #4
        yeah you need to ground the wire that goes to pin 85, or it won't work. you can ground it anywhere, but at MS is convenient, as you can just run it to the case of the ECU.

        I'm just thinking maybe your ignition switch problems have caused a problem with the transistor. The relay mod works fine, the transistor switched relay is just an ideal (for plug and play purposes).
        Build thread

        Bimmerlabs

        Comment


          #5
          well someone on E30tech suggested retensioning the connectors in the plug for the relay after he had a very similar problem. since there was/is a jumper wire pinned into the #30 terminal of the relay that is a good possability

          trying that now and soldering the jumper to the #30 wire on the bottom of the connector. i will report back with the results.
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            #6
            well i tweeked the ends and grabbed a power probe 3 so i can read the voltage.

            still no good.

            here are the results:
            OFF / ON
            #30 11.7 v / .9 v
            #85 11.2 v / (+) 0 v
            #86 11.7 v / .9 v
            #87 11.7 v / 3.5 v
            #87 11.7 v / 3.5 v


            also, is there a way to take off the back of the ecu harness to expose the wires to test or do i need to just stab the wires?

            i may have ran the battery down a bit, if i am showing just under 12v will it be enough to trigger the relays? i have the charger on the battery now.
            Last edited by der affe; 05-31-2012, 12:10 AM.
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              #7
              you can unscrew the cover from the harness and pull it off, you just won't be able to lock it to the case.

              9-10v should be enough to trigger the main relay. I know because that's how bad my battery was getting before I got a new one last year. :p

              I never had the jumper wire "stuffed" into the pin. I soldered it on.

              I'm strongly suggesting you give the relay mod a try, I can't think of anything else.
              Build thread

              Bimmerlabs

              Comment


                #8
                Before I go digging into the ms unit itself, I want to make sure there is no wiring issues causing it to randomly malfunction first.

                If the relay circuit was bad in the MS, wouldn't it show up as a malfunction with it being run on the stim?

                And when I stated stuffed, I was refering to the small red wire jumper that is held into the top portion of the main relay at the connector plug by the #30 male spade of the relay.
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                  #9
                  No, the stim powers the MS directly. the relay circuit activates the main relay, which then powers MS. the stim doesn't do anything with the relay circuit.

                  you could also check the solder joints around the transistor, resistors, and jumper wires.
                  Build thread

                  Bimmerlabs

                  Comment


                    #10
                    here is a link to my thread on e30tech
                    http://www.e30tech.com/forum/showthr...65#post1310465

                    that will save me reposting my findings
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