Loss of Power on Take Off

[fla115]

Yesterday I experienced a loss of power on my 1976 7KCAB ( fuel injected) after takeoff in a climbing left turn at 1500 ft. After getting the nose down and turning the boost pump back on the engine recovered and I made an uneventful landing, but the engine was running badly.

A while back I had posted a thread about my engine popping with an occasional backfire at low idle. A few other owners said they had experienced this problem. The problem could not be correcetd with the idle mixture and the mags and fuel pump were new and OK. We checked for vacuum leaks and everything else to no avail.

The culprit is the servo, it has the original black diaphrams and has never been overhauled. TT on engine is 1500 hrs, with 30 SMOH. I bought the plane in Feb. We have removed it for overhaul.

One of the symptons of a deteriorating diaphram is popping and occasional backfires at low idle.

Just though some of you would like to know this, and if you have the popping and backfire at idle and it cannot be corrected wth idle mixture you should take it very seriously, it is not normal.

Fla 115

 

[hag]

FLA115:
30 SMOH but the servo wasn't overhauled? I wouldn't consider returning a customer's plane to service with an overhauled engine that didn't include overhaul or replacement of the mags and fuel system parts (servo or carburetor, fuel control unit and engine driven fuel pump) It's standard practice AFAIK.

Hag

 

[fla115]

Hag, thanks for your response. You are correct in that the servo should have been overhauled at the same time as the engine.

It turned out that the problem was not the servo as the problem persisted after we installed the newly overhauled unit from Bendix. They are still sending them out with the unit too rich for high temp operations. They work find in cooler weather but require leaning at temps in the mid 90's.

Thanks for your reply and I hope this entire episode helps someone else out who encounters the same problem. It has been an absolute nightmare before we finally found out what was causing the problem.

Steve