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Spark plugs black on #1 cylinder only

in 912 / 914 Technical Questions 8 years ago
Both spark plugs in cylinder number one are black[ like very rich] all other spark plugs in the other cylinders are running a normal light brown color.the 914 eng. has 100 hrs. tt from new

  • Re: Spark plugs black on #1 cylinder only

    by » 8 years ago

    I Nill do you have any mag drop ?
    do you have a temp indication of your water or cylinder indication on that #1
    most of the time blaky sparkplugs will be cause by cyl temp being too low
    and / or air leak ........if you have an air leak your engine should be shaking
    also your baffles could cause this problem if it is a new installation ?

    let me know

    Phil
      
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  • Re: Spark plugs black on #1 cylinder only

    by » 8 years ago

    Hi Nils,

    Don't judge your plugs if you have been idling for a while. First is this a dry black soot or a wet oily plug? If it is dry black soot it may be normal at idle and goes away at higher rpms. Run the engine up around 4K rpm for a few minutes or go fly and then do an immediate shutdown without a long idle and taxi time. Then look at the plugs.

    If it was just dry black soot that should be gone if you oily wet plugs you have another more serious problem. If they are wet oily then start with a differential compression test.

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

      
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  • Re: Spark plugs black on #1 cylinder only

    by » 8 years ago

    Thank you for your reply, I think you were right on with your response the black sooty plugs on number one cylinder was most likely caused by doing a series of runner-up's in changing the pitch of the prop and balancing the carburetors. I did compression check and all the cylinders were about the same. since your response I flew it and that seemed to clear up the problem.
    Thanks Nils
      
    Report
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