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Spark plugs

Plenty of failure points between the mag drive gear and the spark plug tip, the spark plug is the easiest to replace and likely gets the blame for other problems up the chain. I'll stick with my tried and true pressure test, it has worked fine for me for over 40 yrs. As far as brands go, I'll install whatever flavor the customer wants, they all work fine with hot mags timed properly.
So you are willing to providing your customers only half of the tests that are required for spark plugs? How much an hour do you charge that you cannot spend 3 minutes to check the resistance on 8 spark plugs in a cub? Its an easy check and I personally have found enough failures to continue. Oh and my work has 50 airplanes in their flight school, and 15 of them are Lycomings so I am seeing more use and abuse issue than I ever did with most private GA customers. Tim
 
I guess it is hard for me to see a spark plug passing a pressure test on my spark plug tester and failing an ohm test. Maybe I will find one.
You will if you start doing the test Steve, unless all of your customers are like Windy who have to change some yearly because she is flying 4-500 hour per year.
 
So you are willing to providing your customers only half of the tests that are required for spark plugs? How much an hour do you charge that you cannot spend 3 minutes to check the resistance on 8 spark plugs in a cub? Its an easy check and I personally have found enough failures to continue. Oh and my work has 50 airplanes in their flight school, and 15 of them are Lycomings so I am seeing more use and abuse issue than I ever did with most private GA customers. Tim
Guess I haven't seen the requirement nor the need. Haven't had any complaints nor seen any issues by not doing this test. I do pressure test with a spark plug test although you and the Tempest marketing department say that is not enough. I guess I will have to have an issue that proves me wrong.
 
Guess I haven't seen the requirement nor the need. Haven't had any complaints nor seen any issues by not doing this test. I do pressure test with a spark plug test although you and the Tempest marketing department say that is not enough. I guess I will have to have an issue that proves me wrong.

Apparently the slick mags require the resistance to be within limits or it will cause premature coil failure.

Tim
 
So you are willing to providing your customers only half of the tests that are required for spark plugs? How much an hour do you charge that you cannot spend 3 minutes to check the resistance on 8 spark plugs in a cub? Its an easy check and I personally have found enough failures to continue. Oh and my work has 50 airplanes in their flight school, and 15 of them are Lycomings so I am seeing more use and abuse issue than I ever did with most private GA customers. Tim

Please show me where a resistance check is required on spark plugs other than Tempest. Champion Aerospace disagrees with the requirement.

From Champion Aerospace Service Letter SL74-20-001

"It is our opinion that the 5,000 ohm service limit for aviation spark plugs, currently being published inmarketing literature by our competitor, is an erroneous and unsubstantiated limit. It is our opinion thatthis supposed limit was not selected as a result of any actual testing, but somewhat arbitrarily basedupon the inherent characteristics of the resistor design and the manufacturing tolerances provided tothem by their foreign supplier for spark plug core assemblies."

You can read the whole SL here https://www.championaerospace.com/assets/technical/SL74-20-001.pdf

As far as my customers go, I'm fairly certain they keep coming back because they trust my judgement.
 
I posted a link to the Taylorcraft website where I posted the Mils-pec on plugs...which has a requirement for the acceptable ohms for a plug to be published. I Guess that you didn't read the link? But hey, welcome to the 1980's
 
Please show me where a resistance check is required on spark plugs other than Tempest. Champion Aerospace disagrees with the requirement.

From Champion Aerospace Service Letter SL74-20-001

"It is our opinion that the 5,000 ohm service limit for aviation spark plugs, currently being published inmarketing literature by our competitor, is an erroneous and unsubstantiated limit. It is our opinion thatthis supposed limit was not selected as a result of any actual testing, but somewhat arbitrarily basedupon the inherent characteristics of the resistor design and the manufacturing tolerances provided tothem by their foreign supplier for spark plug core assemblies."

You can read the whole SL here https://www.championaerospace.com/assets/technical/SL74-20-001.pdf

As far as my customers go, I'm fairly certain they keep coming back because they trust my judgement.
Champion has changed their tune since 2012...
 
Requirements aside, I would treat the resistance test as an optional test that can give useful info. I found an intermittent plug this way, and I suspect there are marginal plugs that pass the bomb test but would show up on the resistance test. And, if you're getting mag noise in the radio, this is a quick way to find the deficient plug.
 
Champion has changed their tune since 2012...

Champion no longer uses carbon pile resistors in their spark plugs but their technical rep told me that if a spark plug tests good on the pressure tester it is considered good. No requirement to ohm test. So does the mil spec on spark plugs require them to be ohm tested annually? The FAA calls out the requirements for testing an ELT but I have not seen one on spark plugs.
 
If we had to maintain to mil spec, none of us could afford to fly. The FAA sets our standards. 43.13 has a section on spark plugs.
 
If we had to maintain to mil spec, none of us could afford to fly. The FAA sets our standards. 43.13 has a section on spark plugs.
So you are saying that I can use grade 5 bolts instead of AN which is a Mil-spec? I realize that Diamond, Technam, and Czech us DIN hardware but we are speaking Merican here...
 
AOPA article on the Champion spark plug issue...

Read the article below with an open mind, and I suspect your thinking might change... I respect the folks on this forum tremendously, but Mike Busch lays out a simple and compelling case:

One of the interesting quotes in the article is from the actual Mil Spec for aviation spark plugs (MIL-S-7886B), which states in part:
"4.7.2 Resistor. Each spark plug shall be checked for stability of internal resistance and contact by measurement of the center wire resistance by use of a low voltage ohmmeter (8 volts or less). Center wire resistance values of any resistor type spark plug shall be as specified in the manufacturer's drawings or specifications." (emphasis mine)

After experiencing horrible misfiring on two different aircraft whose mags, harnesses, and Champion spark plugs all passed the "conventional" tests (specifically including the "bomb" testing for the spark plugs), the "resistance test" found very high resistance in more than half of the Champion spark plugs in both plane's engines. In both the turbo-normalized IO-540 Lycoming (Commander 114) and the dirt-simple O-200 Continental (Citabria 7ECA), new plugs – ones that passed the resistance test – immediately resolved the misfiring issue.

Oddly enough (yet not totally surprising), three of the "brand new, still in the box" Champion plugs failed the resistance test before they were ever installed. Ironically, this was just weeks before Champion released their redesigned plugs which eliminated the issue (by basically copying Tempest's design)... Oh, and my A&P told me Champion would NOT replace those "bad" plugs. He had to eat the cost... Maybe that's why he now stocks and recommends Tempest plugs?
 
Doesn't make any sense, Champion Carbon pile resistor plugs will not pass the 5 ohm test ever, period.
I have passed a lot of chamopion plugs for years, I can think of more failures for an open circuit than high resistance. And they all passed the pressure test. I also realize that most mechanics will not change their minds no matter what I say so you do what you feel is best and good luck.
 
Another tool in the tool box. When I have an issue I know where to go. I tried checking some carbon pile Champion plugs, didn't work. Are you telling me the old style carbon pile Champion spark plugs should pass the 5k ohm test as well?
 
I also realize that most mechanics will not change their minds no matter what I say so you do what you feel is best and good luck.
Yea, delivery is everything. Thumping your chest and telling us we are doing it all wrong is the way to win hearts and minds.
 
It is funny to watch an owner's eyes when you ohm a plug and it is high and I take it gently over to the bench, place a rag over it and smash it with a 3lb hammer, that way it never goes back into the airplane...because if they cant afford a replacement plug, they shouldn't

Please send any fine wires pre sledgehammer and I will environmentally dispose them.Will pay shipping.
Thanks,
Mark
 
quote_icon.png
Originally Posted by mike mcs repair
question for SJ,
is there a block user feature on here like on FaceBook???, so we don't ever have to see some users weird post for evermore??? makes facebook so much more enjoyable once you identify them...




There is...


thanks, click the users name and find the option there
 
I'm curious if anyone has tested the resistance of the Champion REM38 fine wires. I tested the four that I use on the bottom plugs and the resistance was all over the map. In round terms 5K, 2M, 9M, and 25M. I'm chasing a small stumble at cruise and trying to find out if it's in the plugs.

Jerry
 
Hey Jerry

I'd check it against a new one first. The ones in the Meg range would make me recheck them. Are you checking them with air pressure?

Web
 
Looks like he is checking with an ohm meter and not sparking them on a tester.
Most people do not check them with a meter cause they will see how inconsistent they are.
 
Hey Jerry

I'd check it against a new one first. The ones in the Meg range would make me recheck them. Are you checking them with air pressure?

Web

No air pressure. Just using a multimeter. I'm not as sold on the fine wires as some and don't have a spare. I did stock up on 4 more Tempest REM 40E and will just throw them at the bottom and see if the stumble subsides. Forgive my dumbness but I have read about (in this thread) pressure testing plugs but not familiar with it or what's needed.

Jerry
 
It's just an old school way of checking the plugs performance. Put it in the tester and increase the air pressure blowing on the spark. Spark should not 'blow out'. If it does, the plug will not fire under compression in the cylinder. I've got one but have not used it in quite a while.

Maybe run down to the parts house and measure the resistance of a new one?

Web
 
It's just an old school way of checking the plugs performance. Put it in the tester and increase the air pressure blowing on the spark. Spark should not 'blow out'. If it does, the plug will not fire under compression in the cylinder. I've got one but have not used it in quite a while.

Maybe run down to the parts house and measure the resistance of a new one?

Web

I thought of the parts store measurement but I think they may be in sealed packs like standard plugs.

FYI - I'm using a Fluke 87V and cleaned the plugs before testing. I would think that would work.

Jerry
 
Do a mag check at 2400 RPM. Just be prepared if you do have a bad plug you will really notice it. You will see what cylinder has a EGT/CHT drop. figure out if mag is top or bottom and replace that plug.
DENNY
 
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