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Spark Plugs

DonMuncy

By DonMuncy
in General Mooney Talk

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DonMuncy Grand Master

DonMuncy

Posted
Posted

My 231 has been running fine, but I had the cowling off for something else and decided to check a few of my plugs. I read somewhere that the resistance in the plug should be around 3 - 5,000 ohms. These are massive Champions. I pulled two and both showed "open", (as in the same reading as when the ohmmeter probes are not touching anything). I checked with both my meters, and I don't think I've suddenly forgotten how to read an ohmmeter. What do the geniuses on this forum think is going on.

KSMooniac Grand Master

KSMooniac

Posted
Posted

You have bad Champion plugs.  There are a lot of them out there these days, despite declarations from Champion that nothing is wrong.  Switch to Tempests (either massive or fine) as yours fail or all at once.  I did it last year (fines) after getting a couple failed Champions within their first couple hundred hours.

carqwik Experienced

carqwik

Posted
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I just put on Tempest massives on my Bravo...about 5 hours of flying since then.  Too early to judge but I switched because Mike Busch of SavvyMX said the Tempests were better in one of his webinars.  Plus they're cheaper than the Champions. 

DrBill Mentor

DrBill

Posted
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When I tested my "old" plugs, I found it very difficult to get a good connection on each surface.  Had to "scratch" both probes to get any reading.

Had the issue even with the new plugs.

BILL

DonMuncy Grand Master

DonMuncy

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Naturally, if I knew the answer, I would not have asked. But I am having a little difficulty with the idea that two plugs both failed between the last time I did a run-up and today. If they had both shown 6, 8 or 10,000 ohms, I would not have been surprised. At this time I am more inclined to go with Dr Bill's theory. The contact surface down inside the plug is bright and shiny, but the nose may have enough crud that my scratching didn't get down to good metal contact. I will try again tomorrow.

Thanks guys.

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tony Mentor

tony

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As a side note, when you get ready to switch your plugs, the tempest plugs require a deeper  socket than the champions. I got surprised. 

MARZ Mentor

MARZ

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Not to divert the thread but I found that I had massives on the top holes and wires on the lower - haven't changed it but just curious if anyone else has seen or heard of this

BigTex Mentor

BigTex

Posted
Posted
Not to divert the thread but I found that I had massives on the top holes and wires on the lower - haven't changed it but just curious if anyone else has seen or heard of this
Mike - Using fine wire plugs in the lower side is a very common technique if the engine has a tendency to fowl plugs.
larryb Mentor

larryb

Posted
Posted

Naturally, if I knew the answer, I would not have asked. But I am having a little difficulty with the idea that two plugs both failed between the last time I did a run-up and today. If they had both shown 6, 8 or 10,000 ohms, I would not have been surprised. At this time I am more inclined to go with Dr Bill's theory. The contact surface down inside the plug is bright and shiny, but the nose may have enough crud that my scratching didn't get down to good metal contact. I will try again tomorrow.

Thanks guys.

 

Just because you read open doesn't mean you won't get a spark. You could have a tiny gap inside, and spark across both that gap and the main gap. Another theory I have read is that the Champions are temperature sensitive and will show a lower resistance once heated up. So it doesn't mean that your bad plugs failed since your last run-up.

 

I had a few of my plugs read high a year ago, and switched to the Tempest fine-wires. I've got about 100 hours on the Tempest. My run-ups are more consistent than with the Champions. 

 

Larry

DonMuncy Grand Master

DonMuncy

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Dr Bill was right. I sharpened the ends of the probes of my ohmmeter and wire brushed the center electrode of the plugs. Voila, I get an ohm reading. The bad part is they both read about 9,000 ohms. I plan on looking at how many hours I have on these plugs and then make a decision about tossing them. Being cheap like I am, tossing $350 in plugs for some unknown (and likely small) change in potential fuel burn and/or power, is going to take some contemplation.  

Would all of you replace these plugs if they have 100 hours on them?

N601RX Grand Master

N601RX

Posted
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See if your mechanic or someone around your filed has a tester that will fire them under pressure. My IA has one that will clean the plugs, and then fire them. You can adjust the air pressure while doing this. I had a champion with 26 hrs on it that would fire fine at ambient pressure, but around 80psi it would stop firing.

Danb Grand Master

Danb

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I also switched to the fine wire plugs in my Bravo and I could not be happier, temps. are better in the flight levels no fouling etc. a great choice. Safe flying

BigTex Mentor

BigTex

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FWIW i swapped my plugs for the fine wires and my little C model couldn't be happier. It made a huge difference. The engine still has a smile on its face. :)

PTK Grand Master

PTK

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Running Champion massives with no apparent problems. I haven't checked resistance. When the time comes I'd be tempted to go with Tempest fine wires. The way I see it the cost is a wash because they last at least twice as long as massives.

Here are recent flight test profiles. An in-flight lean mag check and a GAMI lean test, both at 9k.

Besides the timing which I'll have better tweaked, can anybody comment? Is there anything out of the ordinary?

post-7035-0-98621500-1379542188_thumb.jp post-7035-0-31262100-1379542156_thumb.jp

DrBill Mentor

DrBill

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When I found a plug out of spec, I changed the 4 highest.  The next annual, I changed the other 4.  Spread the cost over a year and now I have some "good" spares.  Courtesy of my A&P I have some really bad ones. I'll take some pictures tomorrow and post here.  It's amazing how egg shaped the electrode can get.  So, besides a high ohm reading, and oblong electrode is what my A&P looks for. Oh yea, I use Tempest Massives since I don't have a fouling issue.

BILL

DonMuncy Grand Master

DonMuncy

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I don't know whether it is a blessing or a curse, but Tempest doesn't sell fine wire plugs for K models (turbos).

PTK Grand Master

PTK

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..It's amazing how egg shaped the electrode can get. So, besides a high ohm reading, and oblong electrode is what my A&P looks for.

These we donate to the American Bonanza Society!

  • 2 weeks later...
DonMuncy Grand Master

DonMuncy

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Parker,

I think you are right. It has been a while, but I think I looked at their chart and my brain said that the "Xs" meant they didn't have them. It appears that the xs are which ones are available.

Thanks for the correction. For anyone I misled, I apologize.

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