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 Gentlemen, I am in process of doing my spring readiness on my Rotax 912 in an RV-12, including new spark plugs.  the engine is 6 years old and has 450 hours on it  Upon doing a run up I found a miss on B ignition.  Removing the spark plugs and inspecting revealed that #3 top spark plug was not firing consistently as noted by the color.  It was still somewhat shiney while the others were somewhat sooty.  Swapping out that plug with another new one made no change.  I removed the plug connector from the wire and found that the end of the wire looked black, as well as the pin in the connector.  I cut off about half an inch of wire and found it to be nice and shiny.  I decided to cut open the connector so I ordered a couple of new ones.  I also removed the insulation from the cut off wire.  Actually the internal wire looked very good except for right at the very tip, and the pin looks like it penetrates the wire by nearly a 1/2".  I am concerned that my problem may be deeper than just the spark plug connector.  Has anyone chased down an ignition related miss that was identified and was past the spark plug and connector.  Looking forward to any pearls of wisdom here.  By the way, my new connectors will be here Monday and I will post the results.   Thanks....Tom   

  • Re: Misfires Module B

    by » 4 months ago


    I am just having the same problem after new plugs and a carb balance at 400 hours. Thinking it is bad fuel so changed suppliers and yet to give it a try.


  • Re: Misfires Module B

    by » 4 months ago


    Tom, does you issues go away after run up? My misfires tends to burn off after i run the engine at 4500 for a minute or two.


  • Re: Misfires Module B

    by » 4 months ago


    We just finished jumping through hoops with  912is Fuel-injected engine that turned out to be an ignition(Spark) coil that was bad on only one side. 

    The control circuits are different but the actual spark generating components and troubleshooting methods are equivalent. Thread.

    Swapping the connector to see if the problem moved or resolved would have been the preferred choice.

    If the new connectors do no resolve the problem, try swapping ignition(Spark) Coils to see if it makes a difference.

     

     

     


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


  • Re: Misfires Module B

    by » 4 months ago


    ben barron wrote:

    Tom, does you issues go away after run up? My misfires tends to burn off after i run the engine at 4500 for a minute or two.

    Thanks for the replies guys.

    Hi Ben, It is a very intermittent miss.  But no, it doesn't go away after warm up, and when it occurs, it is a hard miss.  the higher the rpm, the worse it feels.  Honestly, with both ignitions on, it is acceptable, but during ignition checks, it falls on it's face.  I'm really hoping that the new spark plug connector fixes it.

    It seems to me that spark plug analysis  is almost impossible on these engines.  When you get a hard miss, the carbs shake so bad that they flood the cylinders with fuel and all of the plugs get wet, making it difficult to locate the problematic cylinder.  I got lucky with new plugs and I was able to detect a difference in the burn pattern.   Looking forward to solving this on Monday when my new connectors arrive............Tom


  • Re: Misfires Module B

    by » 4 months ago


    Well, as promised by Lockwood, my new spark plug connector arrived today.  I measured the depth of the connector, made a mark on the wire, and carefully installed the new connector, making certain that the wire reached the bottom of the connector.  Run up revealed that the exact same problem exists, intermittent miss on B ignition.  So much for my confidence that I had found the problem.  Out of frustration and depression, I just closed up the hangar.  After recovery I will go after it again.  It has been suggested that I swap ignition system as a next step.  Maybe tomorrow.  I do have the add on soft start, but that retards ignition A.  Can't see how that would cause this condition.  My guess is that when I swap ignitions, I need to use B for the start, instead of the normal A.   Oh well, this will keep me busy while we all stay home in response to the virus concerns, but any additional thoughts will be greatly appreciated..........Tom   


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