201J A3B6D bad Champion plugs fry magneto?

[mattbucy]

Recently could not get my left mag to check out satisfactorily in 1983 J with dual mag. Magneto overhauled 105 hours ago. Champion massive electrode plugs were pulled and tested. None fouled but all but one were above 5k ohm resistance and two tested at 15 mega-ohms! These plugs did not have a lot of time on them. New plugs installed and engine seemed happy. But then left mag stopped firing engine reliably again. Magneto pulled and inspected. Left points damaged. Explanation was this: extremely high resistance plugs likely were not firing leaving the spark to find its ground elsewhere, namely the magneto in this case, which damaged points and possibly compromised condenser.

Sound reasonable? Anyone else have problems with Champion plugs going bad like this?

Thanks,

Matt

[wishboneash]

I replaced them with Tempest massives and never looked back. I had several Champion plugs at 100k-300k ohms when I checked. Champion is finally getting around to fixing their design.

[Andy95W]

I replaced them with Tempest massives and never looked back. I had several Champion plugs at 100k-300k ohms when I checked. Champion is finally getting around to fixing their design.

Too little, too late for my taste. I'll stick with the Tempest.

For Matt (OP): yes, I agree that sounds reasonable and likely. Haven't had the same experience, but others have posted similar issues.

[Oldguy]

Had problems with my '84 J fouling plugs on taxi even when leaned. Switched to Tempest massives at annual in September last year and have had zero problems since. I would say it starts easier, too, but the new Sky-Tec starter can probably claim some of that improvement.

 

John

[smccray]

I don't have a clue if that response sounds reasonable.  You might check the leads before you IRAN the mags again.  I had a lead on my J that according to the A&P it tested okay, but he thought the leads were bad.  I went ahead and replaced the leads with a new harness and it solved my problem.

[testwest]

Everyone I have ever flown with has suggested that spark plugs are very prone to "fouling" without perfect technique on taxi out with respect to mixture. I am becoming less and less convinced that lead or other combustion by-product fouling is the actual mechanism in so many bad run-up checks.

 

My theory is this: the plugs are not fouling during preflight ground ops, they are just not sparking across the intended gap in the cylinder. There is empirical evidence to "suggest" (nothing more) that perhaps a high resistance plug may have some dependence on temperature, so that as the plug body and resistor warm up during ground ops, the resistance goes down and finally the spark plug will pass the energy down the center electrode assembly as designed. This may be why the "lean 'er out and burn off those fouled plugs" technique appears effective.

 

I just encountered a bad plug during runup of our '77 J, I know that the data were recorded on the JPI930, but have not downloaded yet. The plugs are fairly old Champions. I'll get more information soon, hopefully.

 

I assume you all have seen the article for the Aerostar group that really increased the awareness on this whole issue. My mechanic, Jim Musgrove, and another pilot with a Seneca here in Seattle were ground zero for the spark plug resistance issue. I discovered the same thing on my Aerostar with Jim's help and wrote this article on the experience, here:

 

http://www.openclip.net/Benchmark/AOALog2011SpringTwoSparks.pdf

 

Tempest has been distributing the article ever since, and their better product and the article combined to basically bring Champion's business in spark plugs to its knees. Champion finally changed their design to be similar to Tempest's, but I bet Champion's Kevin Gallagher has a Normy voodoo doll in his office stuck full of pins.

 

Ever since I changed to Tempest plugs in the Aerostar, I have not had a single bad runup. And this is without changing technique on taxi-out mixture management.

 

So I think "fouling on taxi out" is a big myth.

 

If you have a bad runup and can tell which plug it is, go back to the hangar, pull the plug, clean it and test its center electrode resistance. More than 5000 ohms, note the value and test it again stone cold. It may be higher! If so, I wanna know about it, I feel the need for another article (publish or perish).

[carusoam]

Anyone with a Normy Voodoo Doll mounted in public view may have already missed the boat and would probably miss the boat the third or fourth time too...

Norm,

Consider the carbureted engine for your thesis. My prior C's ability to manufacture large Pb balls was impressive in my first year of ownership. In following years I was able to lean things out during taxi and found fewer and smaller Pb balls.

Is it possible that the less-than-perfect fuel distribution of carburetors could be responsible for the success of the 'lean her out' brigade?

I am glad that you were able to bring light to the plug manufacturing situation with the prudent use of science and technology!

Another thanks goes out to the MS people that have endlessly shared actual data here...

Recommendation for your next research paper... Why do Gill batteries croak at such a young age compared to the competitor? Do you have any Gill experience?

I stopped on the ramp today to look at an Aerostar. Because it was there. That is a much bigger plane than a Long Body Mooney...

Best regards,

-a-

[mattbucy]

Thanks everyone. I just ordered eight Tempest plugs. 

[testwest]