chazking
Well Known Member
First, I fly a Wheeler Express. And, these Vans' forums are very dynamic; I read them avidly; Wheeler's forum is in a coma! So, I hope all y'all will humour me as I search for answers.
I have a random engine stumble (it's heartstopping when it occurs!).
I'm running a Barrett IO540-C4B5 (136 SMOH) with Slick (L) on top & Electroair (R) on bottom (all BY37's). AFP system (FM300 Servo), nozzle tune (AFP), Andair boost pump (PX375-TC; replaced as early model failed), all new fuel & oil lines. New B&C contactors (BATT & Starter), starter motor & alternator (L-60 - only "old" part). Most parts have less than 40 hrs on them.
Since July 2009, there have been seven stumbles (some have been one-time events, some have recurred several times in flight - very puckery). Generally, there is no pattern, e.g., heat or time-of-flight, as they have come @ various points in the flight (2 on T/O ~ 150', in the pattern, and others at alt (5 to 6K').
The fuel system has been completely dismantled, all lines cleared with compresses air and no obstructions. No water in fuel. Electroair has been completely replaced (mag p/u; controller, wiring - MAP not chg'd, but not expected to cause a stumble). Taylor spiral wires (6) rechecked (1/4" "burn" in the wire to #2 - replaced with a new wire).
Replaced panel rocker switches (AML34). Re-checked all panel wiring - all good.
I planned to replace the slick harness with a poly harness. I mentioned my plan to a friend who asked "are the ignition wires tie-wrapped together?"
They were. I was told to separate them. Because the wires are tied together, tightly, a cross-fire between wires may occur (randomly) & that could be the source of the stumble.
There's not much I haven't done to solve the issue, so, I have separated the wires (unlikely to be harmful!) and am going to give it a whirl in the next day, schedule permitting.
This approach seems to make sense. Has anyone had experience with this approach; how did it work? Am I being too anal-ytical? Other ideas are welcomed.
Ch
I have a random engine stumble (it's heartstopping when it occurs!).
I'm running a Barrett IO540-C4B5 (136 SMOH) with Slick (L) on top & Electroair (R) on bottom (all BY37's). AFP system (FM300 Servo), nozzle tune (AFP), Andair boost pump (PX375-TC; replaced as early model failed), all new fuel & oil lines. New B&C contactors (BATT & Starter), starter motor & alternator (L-60 - only "old" part). Most parts have less than 40 hrs on them.
Since July 2009, there have been seven stumbles (some have been one-time events, some have recurred several times in flight - very puckery). Generally, there is no pattern, e.g., heat or time-of-flight, as they have come @ various points in the flight (2 on T/O ~ 150', in the pattern, and others at alt (5 to 6K').
The fuel system has been completely dismantled, all lines cleared with compresses air and no obstructions. No water in fuel. Electroair has been completely replaced (mag p/u; controller, wiring - MAP not chg'd, but not expected to cause a stumble). Taylor spiral wires (6) rechecked (1/4" "burn" in the wire to #2 - replaced with a new wire).
Replaced panel rocker switches (AML34). Re-checked all panel wiring - all good.
I planned to replace the slick harness with a poly harness. I mentioned my plan to a friend who asked "are the ignition wires tie-wrapped together?"
They were. I was told to separate them. Because the wires are tied together, tightly, a cross-fire between wires may occur (randomly) & that could be the source of the stumble.
There's not much I haven't done to solve the issue, so, I have separated the wires (unlikely to be harmful!) and am going to give it a whirl in the next day, schedule permitting.
This approach seems to make sense. Has anyone had experience with this approach; how did it work? Am I being too anal-ytical? Other ideas are welcomed.
Ch
