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I have a 914 with cylinder 3 that seems to be operating intermittently with a majority of the time it does not.  The indication of something incorrect is that after start, EGT for cylinder 3 does not rise.  The other cylinders rise to 900F to 1000F fairly quickly while #3 does not and sits in the 200F degree range.  This is a relatively new engine with only about 2 hours on it.  Plane recenlty got its final inspection and now doing some ground testing and avionics configuration.

Last weekend it was fine during all starts and avionics configuration procedures.  Started is this weekend for prop adjustments and the issue is back again.  No/low EGT for cylinder 3 and is rough running.  Reviewed all the throttle adjustments/syncing and still the issue with #3 is present.  We also removed the plug wires for cylinder 3 while running and no change in RPM.  This leads me to believe that either it is not firing the plugs or no fuel to combust.  But if cylinder 1 in front of 3 is firing one would think fuel is getting there as don't they share the same fuel intake?

Also hard to believe it's an ignition module as that would mean both modules have an issue.  Somehow C3 plugs are getting grounded?  Carb/fuel?  Any ideas what else to check or point me in another direction?

  • Re: 914 Cylinder 3 Intermittent Operation

    by » one month ago


    Check to see if spark is present. Sounds like plugs aren't firing.


  • Re: 914 Cylinder 3 Intermittent Operation

    by » one month ago


    I think your best course of action is to contact Brett from LEAF https://www.leadingedgeairfoils.com/

    Brett is in your area and a master Rotax technician. If the engine is new with only two hours on it, it might still be within Warranty. 

     

     


  • Re: 914 Cylinder 3 Intermittent Operation

    by » one month ago


    If #3 is really dead it will run EXTREMELY Rough!
    FIRST, swap the #3 EGT Probe with another cylinder to eliminate the possibility of a dead EGT probe.

    Cyl #3 shares the Carb and Fuel/Air with Cyl#1.
    If #3 has no Fuel Neither does #1.

    Cyl #3 shares BOTH sparks with Cyl #4.
    If #3 has No Spark, Neither does #4.
    It is unlikely that BOTH spark plugs in #3 are Bad.
    Easy enough to pull and inspect the plugs in #3 and then Swap them with the Plugs in #2 to see if the problem moves.

    If it is Not a Fuel/Air problem or a Spark Problem, it might be an induction/compression problem.
    Pull the Valve cover on #3 and confirm that the valves are working as expected.
    A stuck valve will kill the cylinder.
    Then run a full compression check.

     


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


  • Re: 914 Cylinder 3 Intermittent Operation

    by » one month ago


    Check that the spark plug wires are screwed/pushed all the way into the coils and plug caps. If they are not it will cause a weak or no spark.


  • Re: 914 Cylinder 3 Intermittent Operation

    by » 3 weeks ago


    Just to circle back on this to give a resolution in case others run into this.  Sent the whole carb in for inspection.  It turned out to be a couple of things.  There was a plugged idle jet hole and the carb floats were too heavy.  Cleaned the jet needle and new floats and it now purrs like a kitten.


    Thank you said by: Ken Ryan

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