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SPARK PLUG WIRES

in 912 / 914 Technical Questions 7 years ago
#1 Lower spark plug wire fell off on a cross country. Not turbulent and I didn't make a rough landing. I discovered it on mag check before take off. After I plugged it back in, did another mag check and it ran fine but the other circuit is running a little rough (barely noticeable at 2000 rpm but more pronounced at 4000 rpm). RPM drops are very small less than 100 and both sides about the same. Last time I changed the plugs was about 40 hours ago. 800 hours on the engine.

Question. 1) Should I buy a new spark plug harness? How long are they supposed to last? I don't want to buy the new expensive one with the fancy plugs, 2) Is it normal for a wire to fall off? Am I being paranoid?

  • Re: SPARK PLUG WIRES

    by » 7 years ago

    No! it is not common for the plug wires to fall off.

    There is a Spec for that!
    Wrap some twine around the plug cap and attach it to a Pull (Fish) Scale.
    It should take more than 7lbs (30N) of force before it unplugs.
    It is more than you might anticipate.

    You can use the legacy plug wires if you choose.
    The New wires are NOT mandated.

    You are not paranoid.
    But you ARE a risk taker! ;)

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
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  • Re: SPARK PLUG WIRES

    by » 7 years ago

    Hi Ernest,
    You are saying wire, but do you mean the plug BOOT or CAP?
    If it was the plug boot then most likely it was not pushed on correctly. You should always hear the ratcheting sound when pushing it on and you should feel that ratcheting as you push it on. This does happen when the plug boots are not on correctly. If you have to pull a boot off and it's slightly difficult to pull off then it won't fall off on its own.

    If you really mean a wire came out of the boot or off a coil then the wire has been most likely damaged. You can cut these back on the end about 3/8" , apply a dab of dielectric grease on the tip and screw it back in place. trimming the wire back will get some clean undamaged wire for the threaded prong to screw into and hold it firmly in place.

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

      
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  • Re: SPARK PLUG WIRES

    by » 7 years ago

    Roger,
    The cap fell off the end of the spark plug.
    1) How often do you replace the spark plug wire set?
    2 )How do you tighten the metal annular piece in the cap(boot) so it won't allow the cap to fall off the plug.
    3) Why is the left (upper plugs) "mag" running rougher than the lower (bottom)?
    Ernie
      
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  • Re: SPARK PLUG WIRES

    by » 7 years ago

    If the cap just slides off easy then someone has damaged it by forcing it on. You'll need to replace it.
    Plug wires have no required replacement time. Just don't bend and twist them. If you do start to have have an issue then it can be tested, but plug wires aren't expensive. Most plug wire issues occur where it threads into the plug cap. This can be trimmed back to get to fresher undamaged wire then just screw the cap back on.

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

    Thank you said by: ERNEST BITTEN
      
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  • Re: SPARK PLUG WIRES

    by » one year ago

    Hi Roger,

    Below is your post to Ernest a few years age.  The line I underlined in italics seems to contradict the proceeding line.  Should it have read 'this does happen when the boots are Not ON correctly.

    Regards,

    William Campbell

     

     

    Hi Ernest,
    You are saying wire, but do you mean the plug BOOT or CAP?
    If it was the plug boot then most likely it was not pushed on correctly. You should always hear the ratcheting sound when pushing it on and you should feel that ratcheting as you push it on. This does happen when the plug boots are not on correctly. If you have to pull a boot off and it's slightly difficult to pull off then it won't fall off on its own.

    If you really mean a wire came out of the boot or off a coil then the wire has been most likely damaged. You can cut these back on the end about 3/8" , apply a dab of dielectric grease on the tip and screw it back in place. trimming the wire back will get some clean undamaged wire for the threaded prong to screw into and hold it firmly in place.

      
    Report
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