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Aviation spark plug failure

T

TShort

Well Known Member
All-

Interested in opinions / thoughts on plugs.

I have the stock Lycoming from Van's in the -10. Slick mags, with slickstart module. Total time since new is now 220h or so.

Earlier this year I had 2 of the original Champion plugs fail. They had about 160 tach hours, but calendar age was around 10 years. I elected to swap to Tempest fine wires, and changed all the plugs.

Since then all has been fine; the engine starts and runs fine.

Last Wed enroute to CO I stopped for fuel in Colby KS. Pre takeoff mag check showed no ignition on Cyl#3 with the left mag. Pulled cowl, pulled plug and checked it with the ohmmeter; "1". Fortunately I had a new / leftover massive electrode plug with me, so I swapped it out and continued the trip.

I know the failed plug was never dropped. I checked resistance on all of the new fine wires before installing, and all were well within spec. I rechecked this one today with a better meter, and it is reading 8800+ ohms.

Is plug failure like this common? Do I need to investigate anything else with the ignition system?

I'm a little frustrated that the nearly new fine wire plug is already bad (probably 30-40h since install).

Thanks in advance.
 
Contact Tempest

TShort said:
All-

Interested in opinions / thoughts on plugs.

I have the stock Lycoming from Van's in the -10. Slick mags, with slickstart module. Total time since new is now 220h or so.

Earlier this year I had 2 of the original Champion plugs fail. They had about 160 tach hours, but calendar age was around 10 years. I elected to swap to Tempest fine wires, and changed all the plugs.

Since then all has been fine; the engine starts and runs fine.

Last Wed enroute to CO I stopped for fuel in Colby KS. Pre takeoff mag check showed no ignition on Cyl#3 with the left mag. Pulled cowl, pulled plug and checked it with the ohmmeter; "1". Fortunately I had a new / leftover massive electrode plug with me, so I swapped it out and continued the trip.

I know the failed plug was never dropped. I checked resistance on all of the new fine wires before installing, and all were well within spec. I rechecked this one today with a better meter, and it is reading 8800+ ohms.

Is plug failure like this common? Do I need to investigate anything else with the ignition system?

I'm a little frustrated that the nearly new fine wire plug is already bad (probably 30-40h since install).

Thanks in advance.
Click to expand...

Contact Tempest. I believe they will replace the bad plug under warranty since they claim the fine wires should last the life of the engine.

FYI, I have ~ 500 hours on Tempest finewires without issue on my IO-360

Skylor
RV-8
 
I don't think I have ever had a bad plug in 20 years. I can't think of anything in your ignition that would cause an issue. Are you sure you are not having detonation? If not, then I think you must just have really bad luck with plugs. Hopefully it is over now.
 
49clipper

Champion has always been the worst plug on the market. After 20 years of annuals and repairs, I have found hundreds of bad plugs. sometimes with only 50-100 hrs on them. Mostly champions. I told folks never use them but the name recognition is strong. I gave up using a champion plug tester for an ohm meter decades ago. Much more telling. Buy Tempest. If you have a bad one, send it back. typically a massive plug is good for about 450-500 hrs.
 
pa38112 said:
Are you sure you are not having detonation? If not, then I think you must just have really bad luck with plugs. Hopefully it is over now.
Click to expand...

No reason to think so. Stock 260hp lycoming from vans running 100LL and standard mags.

Only thing I have done differently lately is doing leaning tests for injector balancing, so I suppose I could have been in the ?red box? briefly during those tests, but temps (CHT) have never exceeded 360-370, or even close to that.

Would detonation cause failure without any visible signs of damage? The plug looks fine externally.
 
never had a failure in 8,000 hours of flying, love the iridium plugs. come out clean with light brown color. rotate and put back in. :)
IMG-0058.png
 
Never had a problem with the fine wire plugs, but like they said, call Tempest. I haven't seen a product yet that has a zero percent chance of failure. They would probably be happy to find out which batch it was for tracking purposes, if nothing else.

On a side note, I, like you, used to carry a spare massive electrode plug. I figured it would be fine as a spare (and I do believe that). But, last year I elected to just invest in a spare fine wire plug. I figured it's then one less thing I have to repeat maintenance on if I ever do use it, and it would give identical performance to all the other plugs. I'm not saying it's something anyone has to spend extra money on, but to me there's a little value in not having to go thru the added work to order a new one and swap it out later, and know you already have the perfect plug in there.
 
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