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magneto/module failed?

in 912 / 914 Technical Questions 12 years ago
Greetings all. On a brand new 912 uls engine install, engine fires up, everything normal, A magneto check shows one dropping 40 rpm, the other drops 800 rpm. Is there anything else that could cause this other than a failed module? It has zero time on the clock.
thanks

  • Re: magneto/module failed?

    by » 12 years ago

    Hi Mark,

    The engine is run at the factory and tested. I doubt it is the ignition module. It is more likely a wire that has come loose or been pulled on and is disconnected or broken. Check the red wire going into each module plug on top of the engine. Matter of fact double check all of those wires, but especially the red one. Depending on depending on the mag check you can narrow down which module to check on.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: magneto/module failed?

    by » 12 years ago

    Only 40 rpm drop doesn't sound like enough. Obviously, 800 is too much. So I would like to know is if you really hear a BIG drop in the engine during that 800 RPM drop, or are you perhaps experiencing invalid readings from your tach?
      
    Report

  • Re: magneto/module failed?

    by » 12 years ago

    Roger, the wires all connected and secure. By disconnecting the A module, will not start. Reconnect A and disconnect B, starts and runs. Can the modules be interchanged to eliminate other causes ie trigger coils or other cause?
    regards,
      
    Report

  • Re: magneto/module failed?

    by » 12 years ago

    Robert yes a big noticeable drop and indicates on tacho about 800 rpm. See reply to Roger above. Seems to be the B Module where the problem is as will start and run with A only connected.

    regards,
      
    Report

  • Re: magneto/module failed?

    by » 12 years ago

    Hi Mark,

    What rpm are you doing your mag check at? 3400 rpm should be right around the 50-60 rpm drop. Some tachs aren't very accurate and others hard to read well, but so long as they are close and you can see the relationship between the two mags you should be okay. Yes for testing purposes you can swap mags. Remember which is which on the plugs or mark them with a felt tip. I still bet you have a bad wire on the "B" module. Track those wires. Many owners thought they had a good connection when they later discovered by pulling on them it was hanging by a thread or broken inside. Check your ignition switch too. If any recent maint. has been done look in that area for a bad wire. I still don't think it is the ignition module.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report
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