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Topic-icon New Oil fouling on #4 cylinder PA 28R-200

  • STEVE ELLS
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1 week 1 day ago #2236

Hi Tom;
There could be two reasons that come to mind. First, it's possible that the oil drain back tube from the upper part of the #4 cylinder is partially or completely clogged. This would result in excess oil flowing past either the intake or exhaust valve guide into the cylinder.
Or, for some reason excess oil is getting into the upper part of the cylinder past one of the valve guides.
You say it's hard to start. It sounds like it runs rough after you get it started. That can mean the one of more of the exhaust valves is sticking in the valve guide. This sticking valve situation is usually caused by either too much lead build up in the inside of the exhaust valve, or excess carbon between the valve stem and the valve guide.
After you check to see if the drain back tube is clear, and find that it is, I recommend that you pull the valve cover on the #4 cylinder and take a good look at the exhaust valve; attempt to push the stem of the exhaust valve back and forth. You're looking for excess movement; there shouldn't be much.
To further check for the possibility that the exh valve is sticking, ask your mechanic to pull the rocker arm, and with the piston down in the cylinder, see if the valve can be easily pushed down (opened). The movement should be smooth and the valve stem should go up and down vertically; side to side movement should be at a minimum.
Let me know what you find,
Steve

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  • STEVE ELLS
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1 week 1 day ago #2235

Hi Steve,

In the last four to six hours, my Arrow has been dripping oil into the #4 cylinder, fouling the spark plug , and causing delayed starts and rough running for 15-20 seconds until the oil is burned off.

We have 500 hours before TBO and have not experienced this problem before. Oil consumption has not been excessive by any measure, and starting has never been an issue.

As a test, the #4 plug was removed and cleaned of oil and then reinstalled. The start process was just as it had been before the problem occurred. We waited 30 minutes, checked the plug, and there was oil in the cylinder.

Compression in all cylinders is very good. We fly 60-70 hours per year, no excessive temperature issues of any kind.

Any thoughts on what is causing this problem, particularly so suddenly?

Tom Thompson

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