What’s this white stuff on the spark plugs?

Discussion in 'Maintenance Bay' started by Aviator305, Feb 13, 2019.

  1. Aviator305

    Aviator305 Pre-Flight

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    A7A23831-37D4-444F-9A83-3B677C3832F5.jpeg 751B43D2-875B-4106-8B5F-C6185CACA49C.jpeg

    This white residue was on all of my spark plugs at annual. Is this lead bromide from LOP operations? These plugs were installed after major overhaul and were not changed or cleaned for 100 hours. The first fifty hours consisted of ROP fly-it-like you-stole-it for break-in. The next 50 hours I was mostly at 55% power somewhere between peak EGT and LOP on my leanest cylinder. This is on a Lycoming O-540. (The plugs were replaced at annual)
     
  2. Kenny Phillips

    Kenny Phillips Cleared for Takeoff

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    The normal ash should be light tan colored, the ash of the fuel burn with some lead deposits; I suppose you could get it tested, but if it was running OK, no problem. Yours look a little funkier than what I pulled out of our O-300, but I did that every 50 hours.
     
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  3. Aviator305

    Aviator305 Pre-Flight

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    It was running OK for the most part, but the mag checks were always rough unless I leaned up to 2000RPM (set MP so that RPM would go to about 1950, and then pulled back mixture so that RPM would climb to 2000). Just wondering what this is because it didn’t look like anything I could find on the web or in Busch’s books.
     
  4. Clip4

    Clip4 En-Route

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    A combination of combustion products and lead, but the gap exceeds specs.
     
  5. Aviator305

    Aviator305 Pre-Flight

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    Thanks
    Do you know if any particular behavior on my part could have contributed to the gap exceeding specs within only a year of use?
     
  6. Katamarino

    Katamarino Cleared for Takeoff

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    It's normal for the gap to widen with use. You just clean and re-gap them and throw them back in.
     
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  7. Kenny Phillips

    Kenny Phillips Cleared for Takeoff

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    Yep. On automobiles and motorcycles, we just replace them, because they don't cost as much as a good steak each.
     
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  8. IK04

    IK04 Pre-takeoff checklist

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    It's primarily lead. We used to put TCP into our C-152s gas to keep that stuff to a minimum. It barely worked with those early, low compression O-235s.
     
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  9. Clip4

    Clip4 En-Route

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    Spark plugs wear out due to normal erosion of the electrodes. Notice the center electrode has a slight football shape. There are tolerances for both gap and total wear.

    If you want really good run ups, clean, gap and rotate every 50 hours. You will notice the bottoms plugs will be dirtier than the top due to crap collecting in the upward facing plug.

    The O-540 is a little hard on plugs.
     
    Last edited: Feb 14, 2019
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  10. Aviator305

    Aviator305 Pre-Flight

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    Here is another opinion that I would like to share.

    “What I'm seeing in your photos appears to be ash fouling, not lead or oil fouling. Ash fouling can be caused by fuel or oil additives, or by having a too-cool heat range spark plug installed. It's actually indicative of the plug running too cool, not too hot. The heat range of the spark plug is chosen to get the plug to run hot enough to prevent fouling but not so hot as to cause preignition.

    Your O-540-Jxx is approved to use three different spark plugs: REM40E, REM38E, and REM37BY. I can't tell from the photos whether you're using REM38E or REM40E, but if you're using REM38E you might want to change to the hotter REM40E to reduce fouling. If you're using any aftermarket fuel or oil additives, you might try discontinuing their use and see if it reduced your ash fouling problem.”

    So, I’m going to check my new plugs now that they have 20 hours on them; if the fouling persists, will try REM40E. As far as additives go, I’m only using CamGuard, and I do not think that is contributory.

    Thanks again all. Much appreciated.