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Thread: Ignition Gremlin

  1. #21
    Super Moderator Av8r3400's Avatar
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    Default Re: Ignition Gremlin

    From what I was told by every Rotax tech and expert I spoke to, this is extremely rare. Modules are usually like light bulbs, either they work or they don't.

    Describe the problem you are having. I've become a reluctant ignition expert in my own right…
    Av8r3400
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  2. #22
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    Default Re: Ignition Gremlin

    Have you checked trigger coil gaps? They can make it idle poorly.
    The trigger coils activate the spark plugs. I believe the spark plug gap should be .022 to .035. According to both Ronnie Smith & Eric Tucker Maintenance & Heavy Maintence Trainers it is better to set the Spark club gap at the low end, or .022. The trigger coil gaps depend on the style of trigger coil you have. If you have the "old Style" the gap should be .016 to .022, for the trigger coils with clamps the Gap should .012 to .016. According to Bryan Toepfer (CPS), Ronnie Smith & Eric Tucker, they should always be checked before putting an engine back in because they can move.
    Paul Zimmermann
    LSRM-A
    Garland, Texas

  3. #23
    Senior Member Dusty's Avatar
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    Default Re: Ignition Gremlin

    Trigger coil gaps?
    How are these adjusted? There appears to be no movement available,do the brackets need to be bent
    I have been having some problems, 6 partial failures resulting in 2 forced landings. We can't reproduce these failures on the ground.
    Testing found one broken wire.Out of desperation I have replaced the stator,pickups and modules with low time items that are known to be good.
    The modules are now mounted on the cabin side of the firewall,the red stator wires and pickup wires are long enough to reach comfortably(and almost in the centreline of the dynafocal mount,so movement shouldn't be such a problem)
    The wiring to the coils will be extended,hopefully an uneventful test flight will happen in the next few days.
    As a side note my IVO had one blade 11grams lighter than the other two.
    This definitely wouldn't help the wiring and may have been upsetting the carbs
    But the problem was showing up on climb out on the 2nd or 3rd circuit.
    Am I missing something?

  4. #24
    Super Moderator Av8r3400's Avatar
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    Default Re: Ignition Gremlin

    Dusty, what is the engine doing during the failure?

    Does it quit completely or run rough or what?

    Which wire was Broken?
    Av8r3400
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  5. #25
    Senior Member Dusty's Avatar
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    Default Re: Ignition Gremlin

    The engine appears to drop two cylinders randomly,sometimes for a second or two, sometimes longer, it can do it multiple times in succession or once then be good for a while(I havn't had a chance to look at the egt when this is happening)
    The broken wire was on a pickup/trigger.
    The stater had a repaired wire,we had a possible intermittent reading on this but even with wiggling/tugging it was inconclusive.
    Starting is excellent but idle isn't as smooth as other 912's on our field.
    The carbs have been overhauled and rechecked.

  6. #26
    Super Moderator Av8r3400's Avatar
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    Default Re: Ignition Gremlin

    Since the ignitions are split, I would question how it could drop two cylinders completely. Look over the grounding leads going to the coils very, very carefully. Mine were grounded in pairs which could lead to two coils not firing at the same time, making the possibility of dropping two complete cylinders. However, I don't think the engine will continue to run with two cylinders not firing at all.

    I added redundant grounding because I found all of my grounds went to the same point on the ignition system. That worried me in that if that one wire broke, the motor would shut down. The coils were grounded in pairs to that point. Now that single ground buss has redundant wires grounding it to the airframe.

    Has your stator been replaced since that service bulletin came out?
    Av8r3400
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  7. #27
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    Default Re: Ignition Gremlin

    Quote Originally Posted by Dusty View Post
    Trigger coil gaps?
    How are these adjusted? There appears to be no movement available
    It is covered in the Heavy Maintenance Manual but not very well, there are two screws with each trigger coil. It is sort of like adjusting points on an old car. Get the feeler gage (preferably brass feelers) and slide it between the trigger coil & the flywheel, loosen the scores on the trigger coils and adjust it until you can feel resistance on the feeler gage. Repeat the process for all 4 trigger coils. According to Brian at CPS he has found trigger coils out of adjustment relative to the gape on new engines out of the crate.
    Paul Zimmermann
    LSRM-A
    Garland, Texas

  8. #28
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    Default Re: Ignition Gremlin

    Quote Originally Posted by Av8r3400 View Post
    Since the ignitions are split, I would question how it could drop two cylinders completely.
    Each Trigger coil controls 2 cylinders. Go look in the Heavy Maintenance Manual Chapter 74-00-00 page 20. It shows the 4 trigger coils B 3/4, A1/2 A3/4, & B1/2. The Trigger Coils A1/2 & A2/3 control the top plugs, B1/2 & B 3/4 control the bottom, see Chapter 74-00-00 page 19. I would Ohm out the ground & trigger coils to see if I could isolate the fault.
    Paul Zimmermann
    LSRM-A
    Garland, Texas

  9. #29
    Senior Member Dusty's Avatar
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    Default Re: Ignition Gremlin

    The stator was changed a few years back.
    I will get a recheck on the earth wiring,we did add a separate earth.
    The pickup/triggers were the early type,these have been binned.
    I'm not much good on electrics,I hope to have this sorted soon
    Thanks for the help

  10. #30
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    Default Re: Ignition Gremlin

    Have you checked the gap on the trigger coils?
    Paul Zimmermann
    LSRM-A
    Garland, Texas

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