Need help and thoughts, cylinder issues

My partner posted about a EGT issue we were having where the number 3 EGT jumped up substantially over the other cylinders. Everyone seemed to think it was a clogged injector. We have been looking at the problem and need a bit more advice. It now appears sadly the issue may be a cracked cylinder or cylinders.
To fill in a little more history on the aircraft the very first indication that there might be a issue was slightly elevated EGTs on 2 and 3 at takeoff power. I first noticed this on takeoffs after the engine was heat soaked from a prior flight. First flight of the day it did not occur. The strange thing was that at the first leaning after takeoff the numbers would drop and match 1 and 4 and the rest of the flight would be normal. Some days it would be 2 only, another day 3 and some days both. Shortly after seeing this trend we had number 3 stay high throughout a flight. This caused us to ground the aircraft to investigate. Initial thoughts from both the forum and everyone we talked with were a clogged injector.
We took a good look at the engine and there are signs of exhaust residue on number 3. Local A&P felt we had a cracked cylinder on 3 and perhaps on 2. This matched what I was seeing on the takeoffs so I assumed that was the issue.
The cylinders on the aircraft are ECI group A (AD for possible cracking) made in 2003. They had a compression check just a 15 hours prior and were perfect. We are also running 10 to 1 pistons and for the last 200 hours have run the engine LOP. Total time is 780 hours. With further investigation the compression still checks perfect. The A&P questioned his initial cracked cylinder thoughts and thinks we might be seeing casting marks. Looking harder at 3 however it sure looks cracked but not near the barrel interface with the head which is what the AD was about. I am going to post some pics and see what the experts here might think. Engine has always been well cooled and never exceeds 380 degrees in climb and cruise is 350 or less ROP and low 300's LOP. Oil is 180 to 190 at cruise and 205 max on a hot day full power climb.
ECI has provided excellent support. In view of the AD we ordered 4 new cylinders from ECI and they helped by reducing the price. Now we are questioning what exactly might be going on. The area that appears to be cracked is above the spark plugs. Given the symptoms and pictures what does the forum think? We are leaning to changing all 4 cylinders and dropping compression to 9 to 1 however we loved the performance of the aircraft and engine with the 10 to 1's. Would like to keep them if they are not part of the problem. Open to any and all thoughts. Pictures to be attached shortly.

George
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Note that the location of the two possible cracks is below the top of the sparkplugs. The lines running to the spark plugs are casing marks.

Spray some soapy water on the "Crack" and perform a leak-down check. So far I have not read anything to say you have a crack. Why change them if there is not evidence that there is a problem ?
Having said that; it sure does look like a crack in the photo...

A bore scope inspection will shed some more light on the issue.
Take a good look at the exhaust valves.
However, with a good compression test result it may not be a cylinder/valve issue at all.

certainly looks like a crack. Hard to believe there would be a parting line in that location. However, it is hairline and it unlikely anything is leaking through it (confirmed by your compression/leakdown test) While a leak could raise EGT, I just don't see how that that hairline crack could leak enough to cause compression loss. Could be wrong here. THe leakdown with soap may confirm it. However, I would expect compression pressures close to 200 PSI on a 10:1 setup and you may not want to put too much pressure in the cylinder with the prop looming nearby.

My first guess would be pre-ignition or detonation, with the cracking as a symptom. Detonation should decrease EGT, but not sure about pre-ignition. The head is weaker at any opening and a likely source of pre-ignition would be something stuck to the plug or it's threads, possibly concentrating the damage in that are. It is possible there is something else raising EGT that is also causing the detonation, such as timing (timing changes result in EGT changes). A borescope should reveal if detonation or pre-ignition is occurring.

You didn't by chance put in new plugs did you? Incorrect reach on the plugs could do it.

Good luck and let us know what you find.

Larry

We did not put in new plugs. I don't think detonation is the issue. Normally you would see a big rise in CHT in that case. ECI just looked at the pics and they have not seen issues in that area. Tomorrow we will clean the area up a bit and test run the engine again. A bore scope may be the best answer. Have to try and round one up in the CLT area.

George

Doesn't look like a crack to me. Usually you will see a blue-gray exhaust stain around the crack and oil seeping out of it. That particular spot is not an area one typically sees cracks.

Detonation would cause lower EGT, with high CHT. A crack in the cylinder head would not raise EGT. A cracked head would lower cylinder pressure, resulting in less cylinder pressure, less efficiency, lower EGT. Hard to tell, are you running plug adapters/ (18mm.14mm)? With limited data, best to clean the area and monitor.

We are running adapters with the plugs. I will hopefully have a few more data points in the next two days.

Crack where?

Is the supposed crack connecting atmosphere to the combustion chamber, or to the intake valve port? If the latter, evidence of oil and exhaust staining would be minimal, and soapy water and compression test would reveal no leak. A crack to the intake port would cause a lean mixture on that cylinder, especially at partial throttle when manifold vacuum is highest. A crack here could respond to head temperature, presenting a change in mixture only after the engine has been well warmed up, as reported.

Looks like mold parting lines to me. Hard to try and troubleshoot without any specifics given.

Intake leak?

George, I recall similar symptoms caused by a missing hose clamp on one of the intake coupling hoses. (Just because an engine shop charged big bucks doesn't mean they got it right). As the engine warmed up, the hose softened and began letting air leak in, leaning the mixture on that cylinder. It was an easy fix. That was a carbureted engine, though. A similar leak might be expected to have less pronounced affect on an injected engine...??
- Roger

George,
I was working on my engine yesterday and looked for marks where you saw them and there is nothing there on my 0-320D1A. No casting marks there. It has Lycoming cylinders.

Eci.. Cylinders

Think most of the eci cylinders had the seperation problems were the barrel meets the head..knot around the plugs. That does look like a mold crease. My cylinders wasn't the problem..my piston came apart on #1 cylinder and the nichel came off the # 2 cylinder wall on the other.. Didn't have a seperation at all.. I just bought 2 new cylinder assemblies and was done with it..that happen at 200 hrs. The other two are still rolling strong at 80/80.

Wanted to post a follow up on the thread. Went over the engine again checking everything. ECI engineers looked at the pics and said no cracks and what looks just like a mold Line on number 2 matches up to what we thought may have been a crack on 3. Put the plane back together and did two ground runs with no issues. The second was to heat soak the engine.
Took it for a test flight and all was well with excellent balance on the EGT's. Let the engine heat soak on a 92 degree ramp and took off again. Climbed up to 7500 feet and saw rising EGT on 3. Did a mag check and the L plug in number 3 was dropping out. Went back down to fly home and all was well and a mag check revealed no issues at 19.5 inches LOP. The failure seems to be power/altitude/heat related. Hope it's a coil or plug issue. Only other symptom was erratic RPM reading when it was dropping a plug. I hope it's not the lightspeed box. To hot after the second flight to keep working but looks like at least it's narrowed down to ignition. Thanks for the help and will update with the final fix.
Now I have to figure out what to do with 4 flow matched ECI cylinders! Anyone need a set at a great price? ECI has been very helpful but there restocking fee is 25%! Ouch

Glad to hear it's not a cylinder issue or even a valve issue.
I didn't realize you had a lightspeed ignition but the Denso plugs should have been the give away.
Having your lightsped drop out would certainly cause a rise in EGTs and a number of things can cause intermittent problems.
Start with the easy stuff before you worry about the box, it is most likely not the box.
A loose connector on the coil, even a little loose, can cause arching and corrode a clean connection. Happen to me on my first plane with very similar symptoms. I didn't find the problem until after I had replaced the coils and all new ignition wires. It was not until I decided to replace the old RG58 cable with a newRG400 cable that I found the corroded spade connector and that was the cheapest part of all.
Good luck.

Wires

Altitude and power both point to high tension ignition problems.
Just fixed a similar issue on my Cozy with Slck/PMAG ignition. With the slick off #3 EGT would drop off while the engine occasionally stumbled if I was at altitude and fairly high power. With the Slick on EGT would climb. New wires fixed it.
I'd install new plugs and then check the wires resistance. I don't know the spec off hand, but they should all be the same with the longer wires having higher resistance, but all 4 should be fairly close, something like 400-500 ohms probably. Having said that the wires can ohm out ok and still have an insulation fault somwhere. Also look for black residue inside the boots, or blackened grease if silicon dielectric was used...sure sign of arcing.
OR...cheap way, swap out a wire from another cylinder and see if the problem moves with the wire or goes away. In either case the wire was most likely the problem.
Good luck
Tim

Well the engine issue is solved and turned out to be simple. I think two lessons have been learned. Don't try and trouble shoot problems Long distance and if it walks like a duck, talks like a duck it's probably a duck.
Test flew today after plug and wire change on the L ign number 3. No joy and problem still there but only at higher altitudes with a hot engine. Could not duplicate lower or on the ground. Problem seemed to start approaching 6000 feet. Next step was to replace that coil. It was the only original coil on the aircraft and had 700 plus hours. I have not heard of half a coil failing at higher altitudes only but success! The coil changed fixed it and we put 3 flight and 2 hours on her with all temp indications back to normal. Odd failure but were fixed! Now what to do with 4 cylinders?

George

O-320 or O-360 cylinders?

Flow matched ECI standard barrel cylinders with 9 to 1 pistons.

sailvi767 said:

Well the engine issue is solved and turned out to be simple. I think two lessons have been learned. Don't try and trouble shoot problems Long distance and if it walks like a duck, talks like a duck it's probably a duck.
Test flew today after plug and wire change on the L ign number 3. No joy and problem still there but only at higher altitudes with a hot engine. Could not duplicate lower or on the ground. Problem seemed to start approaching 6000 feet. Next step was to replace that coil. It was the only original coil on the aircraft and had 700 plus hours. I have not heard of half a coil failing at higher altitudes only but success! The coil changed fixed it and we put 3 flight and 2 hours on her with all temp indications back to normal. Odd failure but were fixed! Now what to do with 4 cylinders?

George

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George,

If it's an LSE Pasma ignition system that you have and you haven't done any other maintenance to your system other than plugs, I would give strong consideration to replacing the other coil and the remaining wires. The stuff wears. I recently went through some ignition trouble shooting at about 700 hours and I found a bad plug, and two bad wires. The real problem turned out to be a bad Hall effect in the end. If I remember well, Klaus recommends replacing wires at 500 hrs and it's not unusual for the coils to fail approaching 1000 hrs.

BTW, a while back ago I had a severely cracked Lyc. angle valve cylinder that I discovered during a routine annual compression check. The compression on that cylinder was about 15/80! The crack started at both sides of the top spark plug and went almost half way around! The crack was almost invisible and there was hardly any soot visible. It may have happened just prior to the compression check. Any power loss was insidious and I didn't notice any EGT or CHT issues. After I replaced the cylinder, it was indeed apparent I had lost some power with the cracked cylinder. My point is things don't always follow the general rules!

Jerry Esquenazi
RV-8 N84JE 800+ hours since 2007

We actually replaced all the plug wires about 50 hours ago. The plugs themselves are changed out yearly. New set on order. 3 of the 4 coils had already been replaced. This was the sole survivor until now. The failure mode was different then I have seen in the past. One side only and only hot above 6000 feet. Compression is 77 or better on all cylinders. New spare coil on order also. I would advise anyone with a lightspeed system to keep a spare coil on hand. Glad we had one!

George

sailvi767 said:

I have not heard of half a coil failing at higher altitudes only but success!

George

Click to expand...

Half coil failures are about as common as full coil failures with the LSE coils. I have replaced a half a dozen of these coils over the years and 3 of them where half coil failures heat soaked at altitude.
Good job troubleshooting eventually

Mike,
Still gotta get up there to throw that other light in.