douglassmt
Well Known Member
Mine
My plane has always needed the boost pump on in the climb if climbing to more than 8-9000 ft. If I turn off the boost pump before leveling off in cruise the fuel pressure will drop below 10 psi, triggering my alarm. Never had the engine stumble, just turn on the boost and fuel psi comes up to 20+, wait until level in cruise, turn off boost, psi stays at 20+. Mike Seager gave me the sop of keeping the boost pump on in the climb, I'm guessing for this reason.
My theory is the reduced cooling in climb plus the higher pump head (pitch up attitude) results in incipient vapor lock. I put a max reading temp strip on the mechanical fuel pump and I think it registered high at >190 IIRC. I may put a shroud and blast tube on it at annual, but I might not. Boost pump or slower climb rate resolves it. Seems to be worse at higher ambient temps.
My plane has always needed the boost pump on in the climb if climbing to more than 8-9000 ft. If I turn off the boost pump before leveling off in cruise the fuel pressure will drop below 10 psi, triggering my alarm. Never had the engine stumble, just turn on the boost and fuel psi comes up to 20+, wait until level in cruise, turn off boost, psi stays at 20+. Mike Seager gave me the sop of keeping the boost pump on in the climb, I'm guessing for this reason.
My theory is the reduced cooling in climb plus the higher pump head (pitch up attitude) results in incipient vapor lock. I put a max reading temp strip on the mechanical fuel pump and I think it registered high at >190 IIRC. I may put a shroud and blast tube on it at annual, but I might not. Boost pump or slower climb rate resolves it. Seems to be worse at higher ambient temps.