69D with cold cylinder mystery

[YankeeClipper]

Just completed an annual and after all is back together front #5 (copilot foremost) is running quite cool. After a few minutes of run-up the others are too hot to touch but you can hold a palm against 5 indefinitely.

The annual involved some engine control adjustments, but would imagine any such would affect all cylinders equally (mostly).

Things checked:

• excellent compression
• good spark (new sparks too)
• valve springs strong
• Nozzle flow equal to other cylinder
• Mag check normal left to right and back

Any thoughts? Been two weeks of head scratching. Even called an IA with many many hours on these.

[CenterlineT]

Originally Posted by YankeeClipper

Just completed an annual and after all is back together front #5 (copilot foremost) is running quite cool. After a few minutes of run-up the others are too hot to touch but you can hold a palm against 5 indefinitely.

The annual involved some engine control adjustments, but would imagine any such would affect all cylinders equally (mostly).

Things checked:

• excellent compression
• good spark (new sparks too)
• valve springs strong
• Nozzle flow equal to other cylinder
• Mag check normal left to right and back

Any thoughts? Been two weeks of head scratching. Even called an IA with many many hours on these.

I would change a couple of things. I would swap the spark plugs with another cylinder that you know it is hot, and test it again. If no change I would swap the injector. This is much easier if you have a digital engine monitor.

[kbecker]

If you can rest your hand on the cylinder head then clearly there is no combustion going on in there. Air, fuel, spark.

I agree with swapping plugs and injectors, separately of course. I would also make sure you were getting fuel from the spider to #5. No spark could be a magneto or plug wire problem also.