My Lyc O-540 has been hard to start (cold) a few times lately. Twice especially difficult.

I had it in the shop this week getting a JPI installed and when the mechanic went to test run it, he couldn't get it to start. He pulled the plugs and found them out of gap, dirty with carbon buildup and said there was evidence of dirt. He looked in the cylinders and said they had a lot of carbon and some dirt in them.

He cleaned and re-gapped the plugs and got it going. He recommended that I let him clean the cylinders by blasting them with walnut shells through the spark plug holes (in the top, out the bottom). This process is actually laid out in a Lycoming service bulletin (SB1418) to remove carbon buildup.

I haven't found much info on this. I've found a couple places advertising positive results, but haven't read any negatives about it. Anybody here have any experience with this procedure...good, bad, or otherwise? Should I or shouldn't I ($600 for 6 cyl)?

+/- 940 SMOH (edit on cyl info). I've owned the plane for last 2 months and 25 hrs.

Carbon will not make a difference in starting. "Dirt"-what is this? There is something else wrong if it won't start. Check the mags and timing for correct operation. If there is fuel and spark is at the correct time it will start. If I'm reading your post correctly, your engine was topped 25 hrs ago? Have the cylinders had a leak down check AND borescoped? If its got massive carbon fouling and only a few hrs since a top, it sounds like perhaps the rings didn't seat. If thats the case, it needs to come apart and be cleaned up, cylinders rehoned and new rings installed. Walnut shells are somewhat soft and are used in place of glass beads to blast engine parts during overhaul. I myself don't like the idea of putting an abrasive in a place you can't completely clean out. There will be some remaining walnut shells left between the piston and rings. If its just a high time motor and you want to try and clean out some of the carbon, you might run Marvel Mystery oil in your fuel for a while. It is basically a solvent (pig oil) that cleans the internal parts and softens varnish and carbon deposits. It's very popular with the round engine crowd. The USAF used it in their round engine transports for many years. Use at your own risk, your results may vary!

Do you get to keep and eat the walnuts?
Kind of like BYOWNS (Bring Your Own Walnut Shells)

I'd rather investigate what the source of trouble is for the buildup. Cleaning it just to have the buildup continue wouldn't make too much sense...

http://www.harborfreight.com/25-lbs-fin ... 92155.html

RockHopper wrote:Carbon will not make a difference in starting. "Dirt"-what is this? There is something else wrong if it won't start. Check the mags and timing for correct operation. If there is fuel and spark is at the correct time it will start. If I'm reading your post correctly, your engine was topped 25 hrs ago? Have the cylinders had a leak down check AND borescoped? If its got massive carbon fouling and only a few hrs since a top, it sounds like perhaps the rings didn't seat. If thats the case, it needs to come apart and be cleaned up, cylinders rehoned and new rings installed. Walnut shells are somewhat soft and are used in place of glass beads to blast engine parts during overhaul. I myself don't like the idea of putting an abrasive in a place you can't completely clean out. There will be some remaining walnut shells left between the piston and rings. If its just a high time motor and you want to try and clean out some of the carbon, you might run Marvel Mystery oil in your fuel for a while. It is basically a solvent (pig oil) that cleans the internal parts and softens varnish and carbon deposits. It's very popular with the round engine crowd. The USAF used it in their round engine transports for many years. Use at your own risk, your results may vary!

Sorry if I wasn't clear about new cylinders. They were factory new at overhaul. Nothing done since. I had a prebuy done and compression checked good and the a&p adjusted the timing at that time. Its been running fine.

Supposedly any walnut shell residue that doesn't vacuum out of the combustion chamber will burn up and go out the exhaust as soon as the engine fires up.

However....doubt is what is making me ask these questions. I have zero experience/knowledge on this procedure. I have found that Lyc lists it as a Service Instruction, not Service Bulletin.

Here is about the only info I have turned up. The second link is one for the shop where my plane is right now.
http://www.sacskyranch.com/combustionClean.htm
http://www.compliance-aviation.com/pistonpowerrecovery.html

Thanks for the ideas.

Seems like a reasonable option considering how much it would cost to pull all of those cylinders and clean. I agree that walnut hulls will be less abrasive and probably 99% of the material will exit prior to start up and the rest will burn or blow out at and after start up as long as the chambers are mostly dry of oils and fuel. They also need to resolve the spark plug or dirty fuel burn issue you are obviously are not getting a good burn, maybe new plugs, check mags, wiring harness and carburetor fuel/air mix.

That SB-1418 makes the hair stand up on the back of my neck... I did go to the site and look at the pics and read the article.. But... personally I would NEVER put something in a cylinder that you can be sure 100% of it is removed back out of it.. Call me old fashioned........

Plus.. carbon build up in a cylinder will cause the compression ratio to go up, not down... Increasing compression will help in starting a motor, not prevent it from starting..

I haven't performed this procedure myself, so take what I type with a grain of salt, but, talking to those who have, it's a perfectly acceptable procedure for cleaning cylinders.

To allay your concerns, walnut shells are softer than anything in your engine, except some of the carbon deposits and the few rubber O-rings and gaskets, so they aren't going to damage anything. Even if a piece of shell somehow managed to get through the three piston ring gaps between the combustion chamber and the crankcase, it would just fall into the oil sump, and, at the very worst, get slorked out of the sump, through the oil pump, and then into the oil filter. If there were any pieces left over in the combustion chamber, they'd be burned and blown out of the exhaust at your next startup. Of course, the mechanic performing the procedure should make sure and clean up with shop air once done, so that shouldn't really be an issue.

The reason not to have this done is that it costs money and isn't needed unless your engine isn't making full power due to lead/carbon deposits.

Using walnut shells is a long accepted cleaning procedure for engines, even turbine engines. T-56 (Allison 501), Garrett and Pratt all use walnut shells to clean the insides of turbines to remove deposits. Yes it sound zany at first glance, but your not using just any walnut shells. They are broken into a consistent size and cleaned of chaff. Yes there are Mil-Specs for the shells.

The Navy does this to any engine on P-3's, E-2's and C-2's that have excessive deposits, which can accumulate in maritime environments. So if you can do it on aircraft costing hundreds of millions of dollars (the E-2 is about $205,000,000 at the moment), I think a little Lycoming can handle it.

RWM wrote:My Lyc O-540 has been hard to start (cold) a few times lately. Twice especially difficult.

I've owned the plane for last 2 months and 25 hrs.

I don't think walnut shell cleaning will help starting.

I had a real problem with my O-540 Lyc. If it was below 28*F it wouldn't start. Cough, spit and sputter. That's it. Throw a little heat under the cowl 10-15 min fire right up.

Turned out to be clogged primer nozzles. My engine has them on 4 cylinders. 3 were clogged. If you have not checked and cleaned them, do it. Mine will now start easy in any conditions.

G'Day...Rob

I've talked this over with my A&P here at home that I trust and have made a decision. You have to realize that a lot of my skepticism is rooted in the fact that the shop where my plane is is not my regular mechanic. I just sent it there for the JPI because he was the JPI dealer/installer, however, also a full service A&P/IA shop. I've never dealt with the guy, so I really didn't know how to trust his recommendations. I do feel like he is being honest with me and I'm not getting any negative impressions up to this point. I like to give guys the benefit of the doubt, but there are lots of shady folks out there these days.

My mechanic reminded me that carb heat air is unfiltered and this could be the culprit for the dirt in the cylinders. We will also look for any induction system leaks. Nearly all of my flying is off of dirt, so dust is a constant factor. He suspects the excess carbon buildup most likely comes from the engine being run too rich for quite some time.

He was familiar with this type of cleaning in the turbine engines and could understand how it would work in the cylinders of a piston engine. We both agree that this $600 cleaning, if effictive, could save a lot of expensive cylinder work later on.

There are 2 primer lines that have issues that are also likely affecting the starting. One partially blocked and one small leak. We will get those addressed and hopefully straighten this mess out.

I think there were several small issues that combined to make the obvious problem. Plug gap, fouled plugs, carbon buildup, priming system not 100%, air filter a little dirty, and so on. Essentially periodic maintenance.

I'm going to do the cylinder cleaning along with tidying up the other problems and hopefully have a positive outcome that was worth the cost. I will report back on my final opinion of the cylinder cleaning to let others know how it worked for me.

Thanks for your input.

So I assume this is an accepted aviation maintenance technique which could be used on any piston engine like a Franklin?

There is a rather shade tree way to remove carbon without the walnut shells. It is misting water in the intake. Done properly it can clean out the carbon quite effectively. It works so well that in post accident analysis, the absence of carbon or significant removal is one of the leading indicators of water in the fuel based engine stoppage. There is also the lean burn out technique used primarily in radials. You run it on the ground lean for a certain time to burn the carbon out. We did this any time we had a lousy mag check, before we returned to have the mechs check it out. Most of the time it solved the problem.

Personally, any time I find I might have so much carbon that I felt compelled to clean the cylinders, I would pull them. Besides cleaning them I would re-surface the valves & seats. Then again, I can do it myself, so I don't have to pay for the labor. Your carbon could be more of coking from poorly seated rings or a worn oil ring. So you may pay the $600 to do this cleaning, which will work to clean it out, but end up with the same coking down the line (you cured the symptom, not the disease).

If you do the walnut shell procedure you will need to be vigilant about checking for squirrels afterwards.

RWM wrote:There are 2 primer lines that have issues that are also likely affecting the starting. One partially blocked and one small leak. We will get those addressed and hopefully straighten this mess out.

I think there were several small issues that combined to make the obvious problem. Plug gap, fouled plugs, carbon buildup, priming system not 100%, air filter a little dirty, and so on. Essentially periodic maintenance.

I'm going to do the cylinder cleaning along with tidying up the other problems and hopefully have a positive outcome that was worth the cost. I will report back on my final opinion of the cylinder cleaning to let others know how it worked for me.

Thanks for your input.

I think your on the right track!

Good luck and let us know how it turns out...Rob

Sorry if I've missed it, but I dont think anyone's talked about the risks of carbon fouling and rough running yet?
Carbon fouling may or may not have an impact on starting, but I understand it's certainly not desirable if you like to push the engine in most any respect, be that running lean of peak, lower RPM cruise with higher MAP, or extended full power (high CHT) operations. You don't want to encourage hot spots which could cause rough running.
But this whole "dirty" business.... that makes me wonder what he's on about. Does he mean airborne contamination? Sounds odd - checked your filter? There will always be some level of fouling in there from combustion, so best be sure he's not just trying to get some work out of you.

Battson wrote:Sorry if I've missed it, but I dont think anyone's talked about the risks of carbon fouling and rough running yet?
Carbon fouling may or may not have an impact on starting, but I understand it's certainly not desirable if you like to push the engine in most any respect, be that running lean of peak, lower RPM cruise with higher MAP, or extended full power (high CHT) operations. You don't want to encourage hot spots which could cause rough running.
But this whole "dirty" business.... that makes me wonder what he's on about. Does he mean airborne contamination? Sounds odd - checked your filter? There will always be some level of fouling in there from combustion, so best be sure he's not just trying to get some work out of you.

Also heard the hotspots can cause detonation, very bad.