Spark Plug Fouling

[Wistarmo]

1993 M20J MSE, engine time 1250 hours. Was using massive electrode spark plugs.  No problem with spark plugs for twenty years.  Had lower plug on cylinder #3 foul in-flight in 2010, landed and cleared the plug on the ground with lean engine run-up.  Had the plugs cleaned and inspected, nothing obvious. Mags overhauled two months later, 250 hours ago.  No further problems with fouling for the next three years.  Champion fine wire plugs installed 2011, 150 hours ago.

 

My standard technique is to lean the engine as soon as possible after starting, taxi out lean, take off and climb rich, lean to 100 degrees rich-of-peak for cruise, enrichen slightly for descent, landing, and final taxi. 

 

Had fouling of lower plug, cylinder #3 in April of this year found on engine run-up, cleared at that time.  Had the same problem a few weeks later, again at run-up, cleared at that time.  Had the plugs inspected and nothing was found.  Took a four hour trip without event.  On the attempted return trip, lower plug, cylinder #3 again fouled and could not be cleared--again, four hours after inspection.  Had to remove the plug and clean it, and it was definitely lead fouling.   Upper and lower plugs switched.  Returned home and back to my mechanic.

 

Pulled the lower plug on cylinder #3 and saw extensive lead deposits, again after only a four hour flight.  This was also not the same plug that had fouled on the previous flight as the upper and lower plugs had been switched.  The plug tested fine by the ohm-meter and pressure test.  The harness cable tested fine.  The compression on the cylinder was 76/80.  Borescope was normal.  Fuel injectors were cleaned.  The only thing left to do would be to tear down the mag, although one episode occurred before mag overhaul and that was only 250 hours ago.  We did replace both cylinder #3 fine wire plugs with new.

 

I have a JPI monitor and other than when the plug fouls, can find nothing at all unusual.   

 

Plan is to fly for several hours, then pull the plugs and inspect.  If more lead deposits, thinking about replacing the harness and overhauling the mags again. 

 

Thoughts?

[tomn]

I had an overhaul shop discourage me from using the Champion plugs last year. He said they had experienced troubles with them over time in these motors and suggested Tempest plugs which I now have. They have about 50 hours on them and so far so good. Might be worth trying before OH the mags.

[KSMooniac]

I'd measure the resistance of all of your plugs the next time you take them out for whatever reason.  They should be less than 5000 ohms.

Champions QC sucks over the last few years FWIW.  I switched to Tempest fine wires last year.

 

I'd also recommend LOP and don't enrichen on descent, landing, taxi, but that is another debate.    If you don't pour excess lead into the combustion chamber, you won't have lead fouling.  I've never had any in my Mooney in 6+ years now.

[takair]

By chance, does that cylinder have a sparkplug style CHT probe on it? It is usually #3. If so, check that you don't have an extra washer under the plug. If so, it may not be reaching in as far as intended and may run cool. It's a long shot, since it has been in and out a few times.

How is the CHT on that cylinder. Is it possible it is running extra rich?

I've had good luck with the Champion plugs, even with high resistance. I swap between Champion and Autolite (now Tempest) massive electrode every 50 to 100 hours. Could be in my head, but the Champion seem to run smoother for me. That contradicts many posts I have seen. Perhaps I have a set of really good Champions and not so good Autolites. The Autolites do pass the resistance check.

[bumper]

Champion got away with their suppressor resistor design for a long time, but that was with massive electrode plugs that get replaced much sooner than the fine wire plugs. Same crappy resistor design in both plugs, just that it'll rear it's ugly head and have you replacing the fine wire plugs long before the electrodes are worn. 

 

Champion doesn't sell just the resistor, so I attempted to rebuild my failing fine wires (some with over 10K ohm resistance) by borrowing the parts from a set of massives. That would have worked except the inside contact of the fine wire plugs was all corroded away due to the arcing and heat, 

 

I bought Tempests. Cheaper, better. I was tweaked at Champion so also bought Tempest oil filters this time . . . cheaper, better.

 

bumper

[takair]

Champion got away with their suppressor resistor design for a long time, but that was with massive electrode plugs that get replaced much sooner than the fine wire plugs. Same crappy resistor design in both plugs, just that it'll rear it's ugly head and have you replacing the fine wire plugs long before the electrodes are worn.

Bumper,

That makes sense. Will certainly consider that for the next set. My Champions are now eroded beyond limits. It would be frustrating to throw out the expensive fine wires for the resistor design...which seems to be matched for the massive wear out time.

Thanks for to info!

[Wistarmo]

Sorry for the delayed response.  I can see the unpopularity of the Champion plugs here, but all the plugs are clean except for whichever one is in the lower slot in the #3 cylinder.  The resistance on the last plug that fouled was 2800 ohms, which is well within used limits and even within new limits.  All CHT's and EGT's are fairly close with usually no more than a 40 degree spread.

[takair]

Sorry for the delayed response. I can see the unpopularity of the Champion plugs here, but all the plugs are clean except for whichever one is in the lower slot in the #3 cylinder. The resistance on the last plug that fouled was 2800 ohms, which is well within used limits and even within new limits. All CHT's and EGT's are fairly close with usually no more than a 40 degree spread.

Were you able to check I'd it has a plug style CHT and extra washer?

[M20F]

What is you Gami spread?

[Seth]

When I owned my 1967 M20F I had to lean aggressively on the ground or it would foul.  I could usually take care of it on runup.  I got used to leaning and did not have any issues excpet for the following:

 

1)  Extended length taxi distance at large airports

2)  Wet and very humid conditions

 

When there was a combination of both of those - like IAH during rain, I could count on needing to clear the mag during run up.  It only happened maybe a half dozen times where I had to clear the mag during my three years and 500 hours owning the F model, but the new owner called me about 3 months into owning it and needed to know why the plane at runnup was not acting properly.  I suggested the leaning out during runnup to clean the mags and he now is much better at leaning during ground ops.

 

I luckily havent had any spark plug issues in the Missile . . . yet.

 

-Seth

[Wistarmo]

I do not fly LOP or use GAMI injectors, but I actually did a GAMI test and the spread was 0.4-0.5.  Haven't had a chance to look for a possible extra washer yet.  I do lean from engine start-up to take-off, and for ground run-up. 

[Wistarmo]

Went for a test flight today and had fouling of #4 cylinder, left mag.  This is the first time for #4 cylinder.  We have changed fuel vendors in the last couple of months and the timing coincides with this.  Will pull the plugs tonight and see what is there. 

[aaronk25]

Stop running ROP your polluting your engine with lead. Use your modem instrumentation to operate you engine more efficiently and CLEANER!

The only thing you have to watch out for is keeping chts below 380, no higher than 400 and oil 200 or cooler, for sure below 210.

Cars or boats dont run excessively rich for a reason.

Your same power setting at 100 degrees rop compared to peak or lean of peak is puking an extra 2-2.5 or more gallons of crap into your motor. Run leaner keep the parts clean its amazing how much better it will run.

[Alan Fox]

Champion has made more spark plugs than any other plug company ever , they have been doing this for about 100 plus years.....If you people would take the time to read the posts and analyze the facts you would see that it is not the plugs.....If you don't know why there is a problem , than just don't blame the parts because they are a certain brand which you personally don't like....  I personally would switch plugs and see what happens , He did and the problem did not follow the plug.....I would secondly do a egt peak test (Gami test ) and see what the spread is , if it is more than .7 GPH I would swap injectors and see what happens.....Also what is the compression ? how can you try to diag an engine problem without checking the Basics???  (compression , Timing , egt peaks , etc etc...) also check the bolts and the O rings on the intake pipes for leaks......  

[aaronk25]

Could have a overly rich injector, but I doubt it. Drown an engine in fuel and some parts are better than others, champion being probably the worse plug to run rich.

[Alan Fox]

Could have a overly rich injector, but I doubt it. Drown an engine in fuel and some parts are better than others, champion being probably the worse plug to run rich.

Could be a bad spider , or servo.....That's why you check the EGT fuel flow spread...

[aaronk25]

Could be a bad spider , or servo.....That's why you check the EGT fuel flow spread...

Agreed.......mine is balanced almost perfectly, but not at all altitudes and RPM combinations. .1 to .4 variance.

Stuff not working sucks

[Wistarmo]

Sorry, but just to recap:

 

TTAF 1350 hours. Using Champion fine wire plugs for two years. Lower plug cylinder #3 fouled X 2, cleared with run-up.  Pulled and inspected, clean.  Four hours later, lower plug, #3 fouled, could not clear.  Plug pulled and full of lead.  Top and bottom plugs rotated. Four hours later lower plug #3 pulled and had lead deposits.  Put in new fine wire plugs #3.  One hour later lower plug, cylinder #4 fouled, cleared with run-up.  Plugs pulled on #4, clean.

 

Work-up to date:

 

1) Old plugs resistance tested at 2800 ohms (within new limits), bomb tested fine. Confirmed appropriate plugs being used

2) Harness wire tested fine. 

3) Mags overhauled 250 hours ago.

4) Oil changed every 50 hours or six months, last time 25 hours ago, all oil analyses fine, using one quart every six hours, Phillips XC oil. 

5) Fuel injectors cleaned.

6) Fuel divider checked for leaks. Fuel pressure stays at full after engine shutdown. 

7) In flight mag checks OK.

8) GAMI test done two years ago and spread was 0.4-0.5 gph.

9) Cylinder compression 76/80 and borescope normal.

10) JPI during flight shows no abnormalities.  CHT's 375, 345, 365, 365 and EGT diff is 40 degrees.

11) Mixture idle shutoff test shows bump in RPM.

 

I suppose I could do another GAMI test now that the injectors have been cleaned. 

[aaronk25]

Sorry, but just to recap:

TTAF 1350 hours. Using Champion fine wire plugs for two years. Lower plug cylinder #3 fouled X 2, cleared with run-up. Pulled and inspected, clean. Four hours later, lower plug, #3 fouled, could not clear. Plug pulled and full of lead. Top and bottom plugs rotated. Four hours later lower plug #3 pulled and had lead deposits. Put in new fine wire plugs #3. One hour later lower plug, cylinder #4 fouled, cleared with run-up. Plugs pulled on #4, clean.

Work-up to date:

1) Old plugs resistance tested at 2800 ohms (within new limits), bomb tested fine. Confirmed appropriate plugs being used

2) Harness wire tested fine.

3) Mags overhauled 250 hours ago.

4) Oil changed every 50 hours or six months, last time 25 hours ago, all oil analyses fine, using one quart every six hours, Phillips XC oil.

5) Fuel injectors cleaned.

6) Fuel divider checked for leaks. Fuel pressure stays at full after engine shutdown.

7) In flight mag checks OK.

8) GAMI test done two years ago and spread was 0.4-0.5 gph.

9) Cylinder compression 76/80 and borescope normal.

10) JPI during flight shows no abnormalities. CHT's 375, 345, 365, 365 and EGT diff is 40 degrees.

11) Mixture idle shutoff test shows bump in RPM.

I suppose I could do another GAMI test now that the injectors have been cleaned.

Should have been more clear sorry, I think your 100RoP mixture is not burning clean, infact its sooty. Lean more, run peak egt, LOP what ever but get the combustion process cleaner. All your cylinders care is they don't get hot. Keep cht under 400 and your good.

Your also not doing yourself any favors running the champion plugs which are KNOWN to have a higher resistant than tempest. That's why tempest runs ads in aviation magazines showing how to test the plugs because trey know the champion plugs are junk and majority of them will most likley fail the test.

[MB65E]

Could try to run the Tempest 37BY plugs or the Champion 37BY plugs. I've had great luck with them in multiple airplanes. They run really well. Also as mentioned, check your timing to the correct mark on the data plate. During taxi-Lean on the ground until it almost quits. On shutdown try doing a light lean run up 30sec or so. 1200-1400rpm or so to clear the fuel out of the cylinders before shut down. Then pull the mixture to ICO but leave the throttle alone. Just a few little things that could help. I think Champion or Lycoming had this procedure years ago, however, have not seen a doc for it.

Good luck, Matt.

[Wistarmo]

There was Lycoming Service Letter L185B, 1988, which suggested running at 1800 RPM for one minute prior to shut-down in engines running 100LL that were rated for 80/87 octane.  http://www.lycoming.com/support/publications/service-letters/pdfs/SL185B.pdf

 

There was Lycoming Service Instruction 1497A, 2011, which gave detailed leaning instructions for ground and flight operations for Lycoming IO-360's installed in Cessna 172's used in training operations.  http://www.lycoming.com/support/publications/service-instructions/pdfs/SI1497A.pdf

 

 

Mike Busch, with Savvy Aircraft Maintenance, manages a large fleet of aircraft and has a Webinar on spark plugs.  Their practice is to pull all spark plugs at 100 hours and resistance check them.  They have found a very large percentage of the Champion plugs, especially the fine wire plugs, have out-of-limits resistance, even after only a few hundred hours.  There is also a large number with nose-cone cracks in the Champion fine wire plugs.  http://www.eaavideo.org/video.aspx?v=1826468805001

[bumper]

I wonder where this spark plug issue is going for Champion? I suppose it would require a huge investment in new manufacturing equipment to change the design of their aviation spark plugs to correct for the deficiencies in their non-sealed resistor design. Is the market large enough to justify that investment? Or will they sit by and watch customers switch to Tempest?

[wishboneash]

I measured all my Champion plugs and they ranged from 1.5k ohms to 85k ohms. The average, let's say was over 20k ohms! Only two plugs were under 5k ohms (out of 8). The engine ran fine, the plugs tested OK on the bomb tester but I am sure I was giving up some airspeed and could probably push it further LOP if they had lower resistance. I am currently swapping them out for Tempest massives. I measured the Tempest and they range from 750 ohms to 1.05k ohms. The resistance values should be more stable than the Champions over time based on their design.

[Marauder]

I measured all my Champion plugs and they ranged from 1.5k ohms to 85k ohms. The average, let's say was over 20k ohms! Only two plugs were under 5k ohms (out of 8). The engine ran fine, the plugs tested OK on the bomb tester but I am sure I was giving up some airspeed and could probably push it further LOP if they had lower resistance. I am currently swapping them out for Tempest massives. I measured the Tempest and they range from 750 ohms to 1.05k ohms. The resistance values should be more stable than the Champions over time based on their design.

Keep us posted on how they work out for you. I have ahead only 1 bad Champion plug over the years, but many that wore out fairly quickly and not always uniformly.

[KSMooniac]

I had a couple champions fail in less than 200 hours recently and switched to Tempest Fine Wires.