Page 1 of 2 12 LastLast
Results 1 to 10 of 15

Thread: Roughness On Run Up

  1. #1

    Join Date
    Jul 2011
    Posts
    2,575

    Roughness On Run Up

    My Cont TSIO 520 was a little rough on start up from cold in about 45* weather, but seemed to smooth out as it warmed up. After about 10 minutes the mag check was good on the right, but decidedily rough and missing on the left magneto. I didn't have any tools with me nor a spare plug as I have had such good service with this plane that I don't carry either. I used to carry both with a another plane. I have not had any times when this engine fouled a plug which then cleared on run up, so I didn't think that was going to be the cure. I am at Front Range airport, and was glad to find mechanics there on Sunday morning. Its not easy to trace the plug wires from one mag to the plugs since they are bundled together, but the mech pulled all the top ones which have easy access. and of course no problem found. Getting to the bottom ones is harder but sure enough the front cylinder, think it is 5 or 6 on the right side, had a bad plug, half the insulator was broken off of the center electrode, and the shop didn't have a new replacement plug since these are 32 S,fine wire ones. Any we hope to find one locally in the morning. Glad I didn't try to fly, and just hope it would be better in the air. It would have probably run ok on the good plug ,but I would have been given up my dual ignition backup. There is a lot of pr for Tempest plugs these days, but I have always used Champions and seemed to work well, this only the 2nd cracked plug Ive had in over 10 years or about 1000 hours. New ones are about $85 a piece, so its good that they last a long time. The outside of mine look old but the electrodes still look good, even on the broken one. Not sure why it broke, bad plug or backfire starting or just age and chance, but it was no doubt about rough. The FBO has a big screen tv where I got to watch the Longhorns smite the purple toads just as it used to be and should be once again.

  2. #2
    Aaron Novak's Avatar
    Join Date
    Aug 2011
    Location
    Oshkosh, Wi
    Posts
    361
    My big concern would be, where did the porcelain go and what damage did it do on the way out. I've seen them get stuck between valve faces and seats, causing damage that would later lead to a valve failure, as well as a miss . I would scope it will and do a leak down test. As for the failure, 90% of the time its knock causing the porcelain to crack in my experience.

  3. #3

    Join Date
    Jul 2011
    Location
    Clarklake, MI
    Posts
    2,461
    What did the other plug in that cylinder look like?

  4. #4

    Join Date
    Jul 2011
    Posts
    2,575
    Thanks, all the other plugs looked good , normal. We'll see on run up if there are any problems but neither I nor the a& p are expecting any, I think the small piece of insulator just went out the exhaust.
    If the piece had dmaged the valve it would not run well on the other mag which it does like normal.

  5. #5

    Join Date
    Jul 2011
    Posts
    2,575
    I think Im ready to go now, 11am the next day. 2 hours labor at $75 per seems reasonable , but the new plug was $140 and of course that was full retail but even at Aircraft Spruce they are listed at $107 plus tax and shipping. I think the electrodes are made from angel hair, though they say "iridium" which is like platinum I think. And of course with the plane ready to fly now the weather is worse and even have an icing report at 16,000 ft right where I need to fly.

  6. #6

    Join Date
    Jul 2011
    Posts
    2,575
    Ive had 2 flights now and the engine runs smooth and normal.IT'S hard to imagine that taking one spark plug away which takes one cylinder away when running on one mag would make it that rough. One cylinder, of a 6 cylinder engine is 16%, but it feels more like half, it feels and sounds rough. Great to have nice mechs available on a Sunday. What a major step forward in safety and convenience it was back about 1920 or 1930 when engines routinely started using 2 parallel ignition systems., so youve always got that built in back up.

  7. #7

    Join Date
    Nov 2012
    Posts
    1,609
    I would want to know what caused the porcelain to break? In all my years I have never had this happen unless there was another underlying cause. Be it the plug was dropped, preignition..ect.

  8. #8
    FlyingRon's Avatar
    Join Date
    Aug 2011
    Location
    NC26 (Catawba, NC)
    Posts
    2,627
    Quote Originally Posted by 1600vw View Post
    I would want to know what caused the porcelain to break? In all my years I have never had this happen unless there was another underlying cause. Be it the plug was dropped, preignition..ect.
    Dropped on the floor at the last annual.

  9. #9

    Join Date
    Nov 2012
    Posts
    1,609
    Quote Originally Posted by FlyingRon View Post
    Dropped on the floor at the last annual.
    Is this what happened or a guess? If any mechanic did this and did not throw out said plug. IMHO said mechanic should be fired from said job. On an auto, if I drop a plug it don't get used. I have thrown many a new plug out because of this. It happens. But a good wrench would never use a dropped plug.
    Last edited by 1600vw; 09-26-2018 at 01:08 PM.

  10. #10

    Join Date
    Aug 2013
    Location
    Gwinn, Michigan
    Posts
    243
    I have seen broken porcelain on plugs from over torquing to being dropped on floor and reinstalled. As for waiting for another fine wire plug to show up, a "massive electrode" plug would have gotten you home with no problems.

    Bill Landry

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •