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Intermittent (electronic?)breakdown

in 912 / 914 Technical Questions 7 years ago
I would like your opinion on this intermittent "breakdown": today having a one hour flight without any problem, at the time of cutting the engine, slowed down 1800 tr, cut 1st “magneto” (2 seconds of wait), 2nd magneto (again 2 seconds of wait) but then a big slow down #1400tr!
Strange; I thus decide to restart (with no problem at all) and to make a motor test at 4000 tr. 1st magneto, loss of 150 tr (normal), 2eme magneto and then, loss of 1300 tr!
After 5 minutes and a quick visual motor inspection, everything is normal. After lunch (2 hours latter), everything is normal. Flight back 1 hour; everything is normal. Ambient temperature 25°C (we are after the heat wave).

To note, 2 months ago at the time of cutting the engine (after always the same procedure), it doesn’t stop and continue during approximately 5 seconds before finally cut.

I suspect one of the electronic module (noted "RIGHT" on key; but which one is it? How to test it?), the key of Neman (faulse contact?), how test it?
Thanks in advance for support.

  • Re: Intermittent (electronic?)breakdown

    by » 7 years ago

    Hi Eric,
    Because of your note that said it wouldn't shutdown I would check my grounds on the back of the ignition switch and the ones out at the ignition modules. While you're at it put a wrench on all your major ground points.

    When checking wire attachment points remember they may be hand tight, but wrench lose. Put a wrench on all of them and not just your hand.

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

      
    Report

  • Re: Intermittent (electronic?)breakdown

    by » 7 years ago

    Hi Roger,
    Yesterday I tried to reproduce the problem, but of course I did not really succeed. The only reproducible thing it during idle (#1800 tr/min) , when I cut one of the electronic module, the engine turns much smoother on "L" than on the "R" position (with idle at #1650 tr/min). When I test my motor at 4000 tr/min, both position “L” or “R” gives a loss of #150 tr/min
    Then, I inverted both electronic modules and retries. The same observation: the engine turns much smoother on "L" than on the "R".
    I checked the grounds, the wires connected to the key switch (ACS); Everything looks fine.
    Then I conclude this problem should come from somewhere downstream: ignition coil, ignition cable, spark plug connector or spark plugs (which has #160 hours).
    A friend will test my spark plugs and tell me.
    -And you Roger, what do you think about?
      
    Report

  • Re: Intermittent (electronic?)breakdown

    by » 7 years ago

    The first thing I would do is throw those high time spark plugs away. Many of us toss them at 75 hrs and I personally know of no one that goes past 100 hrs. Gap the new plugs af .025 and run your test again. While you're doing that unscrew each plug boot and trim the wire end back about 3/8". Put a dap of dielectric grease on each wire end.

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

      
    Report

  • Re: Intermittent (electronic?)breakdown

    by » 7 years ago

    So yesterday, I have installed a new set of plug.
    And test my engine like I did last time. Exactly the same result:
    The only reproducible thing it during idle (#1800 tr/min) , when I cut one of the electronic module, the engine turns much smoother on "L" than on the "R" position (with idle at #1650 tr/min). When I test my motor at 4000 tr/min, both position “L” or “R” gives a loss of #150 tr/min
    A friend tested my old plug and told me they are fine.
    -What do you think about?
      
    Report

  • Re: Intermittent (electronic?)breakdown

    by » 7 years ago

    You shouldn't be doing mag checks at 1800. You should be up between 3500 - 4000 rpm. If it's good there you're good to go.

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

      
    Report
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