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E30 with S50 and E30 M3 cluster - tach coding plug

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    #16
    Originally posted by ForcedFirebird View Post
    Disconnecting driver side doesn't work, it's a long loop and the dual sender systems have half the ohms. I went through this on the race car when eliminating fuel starvation in long sweepers. I added a 318 passenger side carrier to have an additional return in the carrier. When I hooked up the gauge it would read full at full and half at empty (makes sense). Ended up going back to a single internal pump, swirl pot and external pump to feed the engine.

    So, since you are stuck with the early style single sender system due to the coding plug situation, you will need to do a little wiring. Since the system loops through both senders in a late model, you should be able to disconnect the driver side sender and ground it and/or loop it back to itself. AFAIK all the senders have the same ohms, and the reason they read half when swapping parts around is because the ohms are halved when wired in series. I am saying this without looking at the ETM's, but it's a simple solution.
    great, that is what i thought. thank you.
    '72 2002 pickup | '88 M5 | '89 330is | '89 M3 | '01 Z3M | '11 328xi-t

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      #17
      Forgive my ignorance - would swapping the late model fuel gauge from the 325i into the M3 cluster solve the issue of the fuel level reading properly or is this issue driven by the coding plug specifically?


      MJ

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        #18
        The coding plug dictates the number of cylinders for the tach, and fuel sender type. The gauges themselves are the same.

        Looks like a simple wiring jobber. Went ahead and took some screen shots while answering emails this morning. On the driver side pull the connector, jump the two brown/green wires together:

        Click image for larger version

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        Compared to early single senders:

        Click image for larger version

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        john@m20guru.com
        Links:
        Transaction feedback: Here, here and here. Thanks :D

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          #19
          Originally posted by mjweimer View Post
          Forgive my ignorance - would swapping the late model fuel gauge from the 325i into the M3 cluster solve the issue of the fuel level reading properly or is this issue driven by the coding plug specifically?


          MJ
          It would 100% solve it except for the M3 unit has the red needle. I don't want to swap it over or paint a 325i unit - it'll never match.
          '72 2002 pickup | '88 M5 | '89 330is | '89 M3 | '01 Z3M | '11 328xi-t

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            #20
            Originally posted by e30austin View Post

            It would 100% solve it except for the M3 unit has the red needle. I don't want to swap it over or paint a 325i unit - it'll never match.
            How so? The coding plug dictates the fuel level and tach, AFAIK the gauge internals are all the same (with the exception of a red needle on the m3 clusters).
            john@m20guru.com
            Links:
            Transaction feedback: Here, here and here. Thanks :D

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              #21
              Good discussion guys. I posted my question because I was always under the impression that the coding plug only altered the tach signal and the fuel gauge was calibrated to match the set-up of the car (level sender arrangement/tank size). This could be incorrect.

              In other threads I have read how folks have put a later model 325i cluster in an early 325i chassis and simply swapped the speedo (for correct mileage) and fuel gauge to correct its reading. As with many of those type of threads, there does not seem to be much follow-up from the OP to determine if it actually worked...maybe they also swapped to the earlier coding plug.


              Based on my information I was planning to swap the fuel gauge from my '90iS into the M3 cluster (with the M3 needle) as well as install the E28M5 coding chip into the '90iS coding plug to correct the tach for the M52's higher redline. I am nowhere near getting my swap running but I can try this at some point and report back results. The wiring change looks really easy (thanks for posting the ETM pages) so if I need to make the change it won't be a big deal.


              MJ

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