Engine Experts--Advice Please

[mvivion]

I have an O-360 A-1-A. I have forever had lead fouling problems in bottom spark plugs, as do most if not all O-360's, but argueably worse than most.

At one point, I went to long reach massive plugs in the bottom holes, which helped. Instead of having to clean bottom plugs at 20 hours, I could get away with maybe 30.

Not too long ago, I switched to Iridium fine wire plugs, based on folks stating that these plugs are less prone to lead fouling. Since then (at least somewhere around then-the dang smoke has screwed up my flying so much I'm not sure any more) the bottom plugs seem to foul even worse.

Just recently, the fouling got really bad, and, doing training, I've had to clean the plugs after only 8 hours or so. This is training for float ratings, so a lot of idle power, ups and downs, full power, idle, etc, but nothing different than I've done in past.

Yesterday, the bottom plugs, with about 8 hours on them, were full of clinkers and gunk.

So, any ideas? Is the lower heat range of the fine wire plugs amplifying the problem?

One other note: This engine has always used more fuel than I think it should for a given power setting, but I've been leaning pretty aggressively lately to try to cut down on leading problems. Previous owner said he never leaned, as in never.

Could it be that the carb needs overhaul?

Thanks,

MTV

[MacNab]

Aside form the fact that you may have a carburetion problem have you tried using a lead scavenger like TCP? We used TCP regularly in our C-85 with very good results, but additives can be a hassle to use.

[Steve Pierce]

Mike, sounds like your carb is jetted a little rich. I had the same problem with my old O-235. Had to clean plugs every 25 hrs. or so. Started leaning all the time except on take-off and climb and it eliminated the problem. I used TCP with success but a pain in the butt. I would talk to a carb. shop and see if they will flow your carb.

[mvivion]

Steve,

Yeah, that's what I'm thinking as well. Another thing that may lead one that direction is that on this engine, with a four probe analyzer, the #2 cylinder is always hottest, whereas every other 360 I've met, the number 3 cylinder is always hottest.

I've been pretty aggressively leaning the engine on the ground and in the air, but this seems to be getting worse, not better.

Anyone have other suggestions? I'm inclined to pull the carb,

MTV

[Fortysix12]

I'm no expert. Do you have rough mag checks until the motor has run for a while? Oil maybe.

[MacNab]

Yeah, I'd pull the carb, but I'm no expert either, just a shade tree mechanic.

[Dave Calkins]

Mike, I was just thinking about your fouling problem.

How much time is on the mags on that engine?

Slicks need the 500 hour inspection done. If it's not done, you'll have a less-energetic spark, likely leading to a fouling-prone, hard-starting engine.

I'm very surprised that your use of massive-electrode plugs has given you more time between plug-cleanings. It's just not a very likely scenario.

Get back on this one, please......the time on the mags and also the brand.

DAVE

[Yard Dart]

Fine wire plugs on my float plane were a joke a small piece of carbon welded itself to the electrode. Yard Dart

[Dave Calkins]

Isolated incidents in my opinion, though your opinion doesn't likely feel to be "isolated".

I'm wondering if Mikes massives were a higher heat-range plug than the fine-wires he took out. Maybe they were gapped bigger than normal.

It just doesn't make sense that massives would foul LESS than fine-wires.

Also, Cavy, don't sell yourself short on the use of fine-wires. They have been the solution for 0-360 fouling problems in the Husky's and other 0-360-powered a/c for years.

MIKE?????

Thanks, DAVE

[ground loop]

mvivion,

Where do yo think the source of the carbon klinkers is? How much of the fouling would you attribute to lead?

[Steve Pierce]

I would attribute almost all of it to lead. The engines I work on running car gas have no clinkers. Ones running 100LL are full.

[mvivion]

Been out of town for a while. I called a carburetor expert, and his conclusion was that this problem was not likely to be caused by carburetion. His point was that if it was a carburetor issue, it would affect all cylinders, and you could prevent such a problem by leaning. He suggested perhaps an induction leak was part of the problem, but did not recommend pulling the carb at this time, though he allowed as how he'd be happy to take my money for an overhaul, if I insisted.

Maintenance guys checked for induction leaks while I was out of town, and checked the harness, which looks a little rough. No induction leaks, and the harness checked good.

I'll look into the mags, though I think we are totally up to snuff on required inspections.

I too suspect a difference in heat ranges of the plugs. The only fine wire plugs available are a lower heat range (I think) than what I was running. What I was running were long reach plugs in the lower holes.

One of the mechanics said that when he cleaned the plugs initially, he only cleaned the lower plugs, since that's where the clinkers usually show up. It's possible that there was a substantial amount of junk in the top plugs as well, which then migrated down to the lower plugs, fouling them very quickly.

Flight training on floats with an O-360 is a great way to foul plugs. Those are great engines, but plug fouling is definitely their achilles heel.

To add to my reputation, I was nearly to Tanana on Friday when I started getting some roughness in a Husky. Returned to Fairbanks, cleaned the plugs (65 hours since 100 hour), which were full of clinkers, and went back to work. The mechanics say they are beginning to see a pattern here, and they're thinking it's not necessarily the motors .

I'm done flight instructing for a while in that airplane, so we'll see if I can get a few hours out of it before I have to clean the plugs again.

Thanks for all the ideas, and I'll follow up on the magneto notion.

MTV

[Steve Pierce]

So the problem is only on one cylinder? I didn't see that in the initial post. I would suspect induction or cylider problem if isplated to a single cylinder unless your ignition lead is breaking down when it gets hot or the distributor block contacts are arced real bad on that cylinder.

[mvivion]

Steve,

No, the fouling problem is common to all cylinders. The additional wild card here is that number 2 runs a significantly hotter EGT than the others, and that raised suspicion that it might have an induction leak, requiring the mixture to be set up richer than normal to compensate for that cylinder at idle. Turns out there aren't any induction leaks, so that theory is out. That was a theory proposed by the carb guy, and based on the fact that number 3 is normally hottest, and peaks first on O-360's.

MTV

[bearsnack]

What is your oil burn rate? If you are in the the 6 to 7 hour per quart range, or less, this may be affecting your clinker build up.

[mvivion]

Bearsnack,

I put in one or maybe two quarts per oil change (25 hours).

MTV

[Dave Calkins]

Mike, earlier I was assuming the offending Powerplant was in a Husky.

Is this your 170?

What brand of mags?

I'm just pretty curious. I have a Husky customer who is having increased fouling problems. He's bumping the 500 hour mark on his Slicks.

I'll be doing the 500 hour insp. as soon as he's back from his last hunt.

Thanks for any info.

DAVE

[Greg Smith]

One of the mechanics said that when he cleaned the plugs initially, he only cleaned the lower plugs, since that's where the clinkers usually show up. It's possible that there was a substantial amount of junk in the top plugs as well, which then migrated down to the lower plugs, fouling them very quickly. MTV

Did he put the plugs back in their original positions or rotate them? I know this wasn't a hundred hour or annual, but if they were rotated when they were cleaned (1T to 4B, 2B to 3T, 1B to 4T, 2T to 3B), he put the uncleaned top plugs into the bottom holes, giving the next fouling a significant head start.

[mvivion]

Eddy,

Nope, never touched the top plugs. Since its generally the lower plugs that foul on these things the worst, at "intermediate" plug cleanings (between 100 hrs), we've generally just cleaned the bottom plugs, and usually that's good enough. May not have been in this case.

I've run long reach plugs in the lower holes on a couple of these engines, with standard plugs in the tops, and therefore never rotated plugs, and had excellent service from them even then.

MTV

[JohnS]

I have about 600 hrs with that engine in two birds, had some problems when I put non areo shell oil in the crankcase, I drained it at 15hrs back to areo shell and no more problems? hope this helps

[Cimarron]

It's been a while since I worked at low altitudes and flight training but have seen many problems with people not warming up an engine enough to burn the junk out of the gas. When I would pull the lower plugs at an intermediate oil change to clean them I would also pull the top plugs and using a tube bent at 90 deg blow air throughout the cylinders. It was amazing how much more junk would come out the bottom plug hole that hadn't found its way into the plug yet. Left alone this would quickly foul the lower plugs again.

[mvivion]

Dave,

Bendix mags. They are up to snuff, and the mechs checked the harness the other day as well.

Cimmaron,

I think you may be onto it. I've done that in past, but this time had a guy ready to take a checkride, and had a bad mag drop, so did the quicky. I'm betting at this point that you are correct.

The engine runs just fine and is strong.

John,

Your point may also be well taken. Until this last fall, I ran Aeroshell, which contains an additive package which supposedly helps prevent lead problems. Last fall, I switched to Exxon Elite, which has a different additive package, and doesn't include the same lead scavenging agent.

That may be a factor, but I can't really see how a lead scavenging additive in the oil or not could have much affect on combustion chamber lead buildups. Then again, I don't think like an internal combustion engine.

MTV

[Steve Pierce]

I used to do maintenance on a 180 hp pipeline 172 that would build up lots of clinkers. We ran a spark plug clean out tap thru the spark plug holes and then blow out with air. Man there was a lot of crap in there.

[Dave Calkins]

I totally buy the idea of all that extra crap sitting in the combustion chamber waiting to foul a plug.

Mike, I don't think we got TSMOH and A/F type.

I'll let you guys know how this Husky motor does after I get the mags 500 houred.

[mvivion]

Dave,

800 hours since new engine. Cessna 170, Avcon.

MTV

[dick]

we fly an o 320 - 150 on floats, an o 320 - 160 on wheals, and an o 470 on floats. At recent annuals all lower plugs fouled with lead. This occurs in about 10 hours. This problem only surfaced 2 years ago. The maintenance chief at Univ of Alaska aviation center is experiencing the same problem with their aircraft. We suspect that av gas has been reformulated without and notice to us. Any thoughts?

[Roger Peterson]

MTV, I have had good luck with TCP and lean even on takeoff. As one carb man told me, that is what that control is for. Checked real close for detonation for quite awhile, but no problems.

[tempdoug]

After 7 years mike did you solve the problem?

[mvivion]

Doug,

At OSH last year, I asked a Lycoming rep the question, explaining this history. First thing he asked was how many hours the lower plugs have on them. Duh.... I waddled over to AC Spruce, bought four new plugs, and it's been better since. At least it's back to it's original "need to clean plugs every thirty hours or so" routine, which I can live with.

In reference to the recommendations of too rich a jetting in the carb, I noted this winter when flying in cold temps that the EGTs were HIGH right from takeoff. To me that suggests that the jetting is, if anything a little on the lean side, correct? In any case, partial carb heat lowered the EGTs and smoothed things out for cold weather ops.

Mike

[irishfield]

Don't lose track of high EGT being a sign of running on one plug as well.. or at least a plug not working well. Many think things run "cooler" with only one mag turned on.. but since the fuel doesn't burn fully in the cylinder it makes it into the pipe raising the EGT when you're on one mag or have a bad plug.

[P.o.P]

Definitely the worst engine model I've ever encountered with plug fouling is the O-235 L2C as in a C-152.

Fouling can be so bad that the deposits on pistons strike the cylinder head.

There is a procedure to use a grain blast to remove the lead with cylinders on.


After numerous cancelled rental flights we adopted the LYCOMING method of shut down per a Service Inst.

It did not just improve the situation; it ELIMINATED the problem.


Shut-Down


RPM -1800 -30 seconds (lean mix)

Good time to check mags here.

Reduce RPM to Idle & Mixture to ICO.



LOW Power settings do not provide enough heat in the Combustion Chamber to scavenge the lead.


BTW- The MIL & Airline guys would never put an aircraft away without a Mag Check.

you want to find Ignition Problems on Post-flight NOT Pre-flight.

You really don't want to changes mags or plugs AFTER the aircraft is loaded.

[jgerard]

Over the years I have found that most fowled plugs are ones that tend to have more than 3000ohm resistance even though they fire ok. Also I think a lot has to do with proper engine operation keeping the heat in the engine

1st Always ground lean and lean at all altitudes not just above 5000 msl
2nd On approach do not go full rich and throw on the carb heat. This dumps extra un needed fuel into the engine and with the rich mixture over cools the plugs and helps to foul them out easier.
3rd Avoid letting the prop drive the engine, Do not zoom into the pattern and push the prop full forward, Keep the mix out, prop out, and use carb heat only as needed. When you have reduced power to the point that the governor no longer maintains RPM then you can go full fwd on the prop control. No need for increasing the mixture because you're pulling the power out not adding more. Once in the pattern you can add a little more mixture but don't go all the way in with it. Once you are on final and IF there is a possibility of having to go around then you might want to go full rich on the mixture otherwise no need to dump extra fuel into the engine.
4th Keep cowl flaps closed until on the ground to keep the heat in and slow the cooling effect of the cylinders.
5th ground lean as you taxi back to parking

On both fixed pitch and constant speed prop aircraft avoid full rich, carb heat, all the way back to idle approaches. The rapid cooling is what's adding to the fouling of the plugs. Especially when doing lots of touch and go's

Making power on approaches also helps keep the heat in the engine and it's a more stable and precision approach.

All these things have been what's worked for me over the years in various aircraft/power plant configurations and I never have bad plug issues other than old worn out ignition components. I also run car gas from time to time which cleans out the combustion chambers and plugs better than av-gas

I think the sac-sky rang engineering manual should be mandatory reading for all pilots, Lots of great info in there. Also its worth a guys time to go through the engine manufactures SB and SI to educate your self.

For those of you that have engine analyzers and know how to down load the data and make charts you would be surprised how much change you get in CHT's just by small changes in piloting technique during start up, taxi, approach and landing. There is also a lot more good info on proper use of CHT and EGT gauges in the sky-racnh manual that I won't go into detail with here.

Jason

[Bugs66]

Or run mogas. Problem solved.

[skywagon8a]

Or run mogas. Problem solved.

Buggs, does your mogas have ethanol? Ours does around here.

[mvivion]

Jason,

Yes, I've always done all those things.

P.o.P,

Ive also used the Lycoming recommended shut down procedure since I attended their Piston Engine School.


Bugs,

No mogas on field anywhere near here, and crappy quality gas as well. Lycoming will tell you that you should use some leaded fuel in these engines fo healthy top end..

Pete,

91 Octane mogas in MN is supposedly ethanol free.....supposedly.



The worsening issue was due to lower plugs with about 400 hrs on them.

New plugs fixed that but this engine has always had a little more lead fouling than other 360 I've run. Not ugly....360s do tend to foul plugs a little more than 320s.

MTV

[skywagon8a]

New plugs fixed that but this engine has always had a little more lead fouling than other 360 I've run. Not ugly....360s do tend to foul plugs a little more than 320s.
MTV

Mike, perhaps if you used a plug with the next higher heat range you would have better results?

[Bugs66]

Buggs, does your mogas have ethanol? Ours does around here.

No, we have ethanol free widely available now. A year ago that was a different story. Have you checked www.pure-gas.org? That site is updated regularly. $2/gal savings for me.

MTV, does Lycoming also believe that fowled plugs and crappy ignition is also healthy for a top end?
Good read on TEL disappearing:
http://www.generalaviationnews.com/2...there-a-plan-b

[jgerard]

Mike is it oil or fuel fowling? what color is the ceramic on the plugs when you take them out and look at them before cleaning? I used to have this 2-7" plastic card from champion that you could hold your plug up to and it had a row of pictures on each side showing different types of wear and fowling which was helpful in identifying whats going on in the combustion chamber.

Jason

[skywagon8a]

Have you checked www.pure-gas.org? That site is updated regularly. $2/gal savings for me.

Just checked. This state, left wing Taxachusetts on the right coast, is not on the list. The legislature probably mandated ethanol. They have their own little fiefdom under the golden dome.

[ron]

I have always taxied my aircraft with sufficient lean on the mixture that will give me power to just move the aircraft.Keep it like this and the days of fouled plugs may be over for you.Good luck.Ron.