| Today I made 2 changes to my airplane in an effort to remedy my surging issue. Both changes were made as per suggestions from LMLers.
Change #1 - I removed the in line fuel filter and in line fuel check valve formerly located in the cabin footwell of my airplane. I bought a 28" piece of rubber fuel line and clamped in on the void created by removing these items. I then took the airplane for a flight during which it performed flawlessly as it always does in a first start scenario. I taxied back to my hanger, shut down and let it sit for 20 minutes. I tried a restart but experienced difficulty for the first time. I was not able to restart utill I turned the electric fuel pump on and left it on during the start. I then taxied and still experienced my surge issue. I was able to turn the pump off and fast taxi.
My theory on why I experienced the start issue was that the removal do the check valve allows fuel to pass back though the system unimpeded creating the possibility of a loss of prime at the engine driven fuel pump. I believe that check valve (sniffle valve) needs to be in the fuel line. Comments?
Change #2 - I installed a blast tube and directed the airflow directly onto the engine mounted fuel pump. I started the engine (it was again cool from sitting idle for a couple of hours) and went for flight #2. Again the engine performed flawlessly. I landed, taxied back to my hanger, shut down and let the airplane sit for 20 minutes. I restarted (again had to keep the aux fuel pump on) and began to taxi but felt the surge right away but it was not as pronounced a before and seemed to be lessening. During run up I let the engine run a bit longer than usual at 1800 RPM. When I went back ti idle...no surge. I taxied to the active...no surge and took off. Flew great, landed and repeated the
Et sit for 20 minute thing. I restarted, taxied with a bit of a surge but was able to eliminate it during taxi and run up.
I am not ready to celebrate yet but I definitely see a marked reduction in the severity of the surge and the ability, at least today, to eliminate any surge by simply taxiing and or a bit of an extended run up. I believe the blast air is the reason for the improvement. I believe I should also add a second blast tube with the air directed at the gascolator.
Does this make sense? Any and all comments welcome!
Berni
|