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Thread: Well I tried to fly today

  1. #11
    rocket's Avatar
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    Default Re: Well I tried to fly today

    Quote Originally Posted by mmoyle View Post
    My crystal ball prediction...you will find yellowish bits of plastic in one mag...


    Sent from my iPad using Tapatalk Pro
    Mark I'll see your little bits of gear plastic and raise you one impulse coupler

    Rocket

  2. #12
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    Default Re: Well I tried to fly today

    Recently, I had an excessive rev drop and backfiring on the left mag during the run-up check. After trying the standard remedies to no avail, I tried an old style trouble shoot.
    1. confirm that the left mag supplied the bottom left and top right plugs, right mag vv.
    2. swap both bottom left plugs to top left, and top plugs to the bottom
    3. run-up, left mag still misbehaved
    4. swap bottom right plugs to top right, and top plugs to bottom
    4. run-up, now the right mag is the problem
    5. so it's not a mag or spark plug lead, but one of the (now) right side bottom plugs
    6. on cylinder #1 only, swapped the plugs top to bottom and vv again, and checked the mags. The problem had moved back to the left mag, so it had to be the (now) top plug.
    7. pulled the dud plug and checked it's resistance--110,000 ohms, when it should be more like 3-5000 ohms! Into the bin, new plug, runs fine.
    8. if 6. didn't prove anything, then it could only be the plug on #3 cylinder
    It was a REM40E, not all that old, and had not shown any noticeable degradation until it suddenly failed completely. The previous flight had been quite short (15 minutes).
    It surprised me a bit, as I'd not experienced such a clear cut failure of a plug before.

  3. #13

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    Default Re: Well I tried to fly today

    Always a good idea to check plugs first. One may have failed and it isn’t enough to just spark check them. I got a good reminder of that fact 2 months ago. I spent $200 for an injector when all I needed was an $8 spark plug. All of the plugs showed good spark when connected to the leads and grounded to the cylinder head but one quit sparking at 5 PSI in the tester. I hadn’t seen a failure like that in over 20 years.

  4. #14
    Administrator Steve Pierce's Avatar
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    Default Re: Well I tried to fly today

    Run it on the bad mag for a bit and see which cylinder feels cold. I like to start with the easy stuff.

  5. #15

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    Default Re: Well I tried to fly today

    Quote Originally Posted by Steve Pierce View Post
    Run it on the bad mag for a bit and see which cylinder feels cold. I like to start with the easy stuff.
    Spit on your finger and quickly swipe it on the exhaust stack. If it doesn’t sizzle, that’s where the problem is. Of course if you have an engine monitor, just look at the gage!


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  6. #16

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    Default Re: Well I tried to fly today

    What I'm finding is high resistance/open of champion plugs, am recommending Tempest plugs to owners. Have solved a lot of hard starting/RPM drop problems. Some old timer mechanics claim the Tempest don't last as long, my findings are the Tempest are just as durable. Biggest issue is not leaning on the ground once engine is warm enough, and overleaning in flight verified by melted electrodes! These low compression engines are lead fouled by the 100LL, they do much better on autofuel with NO ETHANOL of course.

  7. #17

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    Default Re: Well I tried to fly today

    Quote Originally Posted by Flyjeep View Post
    I dragged the plane out and tried to start it and it wasn’t firing off so I switched from left mag to both and it fired right up. So I just figured go out run it up and lean it till it cleared. After trying several times left mag just will not clear so back to the hanger.. It drops about 1k rpms it is still running but vary poorly pops and backfires. I’m assuming plugs, it ran perfect last time I flew.
    So now it’s time to get sockets and a torque wrench for my hangar so I can at least check my plugs.
    Cheap stuff first, check the bottom plugs, make sure there are not deposits between the electrodes and inside them, if so clean using one of these. https://www.aircraftspruce.com/catal...theleadout.php
    Make sure you don't have antiseize on the plug tips, will cause big troubles! Plugs are very easy to pull and tell the tale of whats happening in the combustion chamber. https://www.aircraftspruce.com/catal...tplugmaint.pdf

  8. #18
    59pacer's Avatar
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    Default Re: Well I tried to fly today

    Quote Originally Posted by Steve Pierce View Post
    Run it on the bad mag for a bit and see which cylinder feels cold. I like to start with the easy stuff.
    Agreed. I was put off that by the significant backfiring through the exhaust system (or is it 'forward firing'?).
    It was more of a mental exercise to test the mag, check the wiring, and find the dud plug with a minimum number of engine runs.
    Being in lockdown here, I look for an 'acceptable excuse' to go to the airfield to carry out 'mandatory maintenance'.

  9. #19

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    Default Re: Well I tried to fly today

    Quote Originally Posted by at7615 View Post
    What I'm finding is high resistance/open of champion plugs, am recommending Tempest plugs to owners. Have solved a lot of hard starting/RPM drop problems. Some old timer mechanics claim the Tempest don't last as long, my findings are the Tempest are just as durable. Biggest issue is not leaning on the ground once engine is warm enough, and overleaning in flight verified by melted electrodes! These low compression engines are lead fouled by the 100LL, they do much better on autofuel with NO ETHANOL of course.
    I will second the old timer’s opinion. I installed half new Champions and half new Tempest in an engine last year. The Champions held up better. I didn’t have enough of the same brand on hand so I split them and flew the airplane 350 hours. IO-520 on an AgTruck. Plugs can’t hardly get treated worse than that. Full rich and high power except for warm up. Shut down and started for every load.
    Last edited by Jeff J; 04-26-2020 at 08:22 PM.

  10. #20
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    Default Re: Well I tried to fly today

    Tool question, standard 7/8 deep or spend the cash for a plug socket? I know with my motorcycle I had to order a plug socket because the outside diameter was to big by a hair.

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