Raymo
Well Known Member
Ran great until it didn't - cold EGT and CHT at low RPMs
I recently finished my -7A and started flying, which has been enormous fun. Lycoming O-360-A4M out of a 2002 Piper Archer that was wind damaged and had 1100 hours since OH in Aug 2014 (flight school plane).
After the 3rd flight, the EGT and CHT would drop off on the #4 cylinder below about 1400 RPM. We went through the following to get to the root cause:
* Induction leak?
-- Replaced induction tube gasket at the #4 cylinder. Tightened all clamps and torqued all bolts. No help.
* Both plugs fouled?
-- Pulled plugs, cleaned, gapped, checked resistance. All good. No help.
* Mag problem?
-- Mag check at 1700 RPM seemed normal.
* Worn cam lobe?
* No issues with #3 cylinder, which shares the same intake lobe.
* Valve sticking?
-- Borescope showed no signs of issues with the valve movement or bore.
* Idle mixture too lean?
-- Richened idle mixture at AFP servo. Improved idle but not the issue.
* Compression issue?
-- Compression checked was 72/80 (1100 hrs on this cylinder)
* Not enough fuel getting to the cylinder?
-- Blew out the injector line. No help.
-- Checked flow to cylinder with fuel pump on. Bingo. No fuel at idle and a dribble at full throttle, full mixture.
Swapped out the fuel divider and all was well again. Mine will go back to AFP for IRAN.
I recently finished my -7A and started flying, which has been enormous fun. Lycoming O-360-A4M out of a 2002 Piper Archer that was wind damaged and had 1100 hours since OH in Aug 2014 (flight school plane).
After the 3rd flight, the EGT and CHT would drop off on the #4 cylinder below about 1400 RPM. We went through the following to get to the root cause:
* Induction leak?
-- Replaced induction tube gasket at the #4 cylinder. Tightened all clamps and torqued all bolts. No help.
* Both plugs fouled?
-- Pulled plugs, cleaned, gapped, checked resistance. All good. No help.
* Mag problem?
-- Mag check at 1700 RPM seemed normal.
* Worn cam lobe?
* No issues with #3 cylinder, which shares the same intake lobe.
* Valve sticking?
-- Borescope showed no signs of issues with the valve movement or bore.
* Idle mixture too lean?
-- Richened idle mixture at AFP servo. Improved idle but not the issue.
* Compression issue?
-- Compression checked was 72/80 (1100 hrs on this cylinder)
* Not enough fuel getting to the cylinder?
-- Blew out the injector line. No help.
-- Checked flow to cylinder with fuel pump on. Bingo. No fuel at idle and a dribble at full throttle, full mixture.
Swapped out the fuel divider and all was well again. Mine will go back to AFP for IRAN.
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