pjc
Well Known Member
I have been testing my RV-6 with auto-gas recently and have observed some low fuel pressure events (possibly vapor lock/pump prime failures) that have never occurred with 100LL. Its a 90’s era SB RV-6 with the standard (of the time) factory Facet (cube) boost pump and Lycoming engine (O-320) driven pump in series.
The Facet pump rattles happliy when powered and seems to pump fine under ordinary conditions. To rule out a boost pump problem I have a couple questions about how these Facet pumps normally operate.
Questions:
1). The boost pump seems to rattle faster when not primed, but gets a little quieter (and slower) after it self primes when powered before engine start. Is this normal ?
2). If I let it continue to run, it continues to click (rattle) even if I don’t start the engine. There are no leaks and the fuel pressure remains 4-6psi. There are no apparent leaks. I might have expected the pressure to rise a few PSI when the carb bowl and supply piping gets full and the carb stops fuel flow. Presumably the pump might be designed to stall at this point and stop making noise. Mine doesn’t, it appears to continue to run despite hydraulic stall and no flow.
Is this normal behavior?
Peter
The Facet pump rattles happliy when powered and seems to pump fine under ordinary conditions. To rule out a boost pump problem I have a couple questions about how these Facet pumps normally operate.
Questions:
1). The boost pump seems to rattle faster when not primed, but gets a little quieter (and slower) after it self primes when powered before engine start. Is this normal ?
2). If I let it continue to run, it continues to click (rattle) even if I don’t start the engine. There are no leaks and the fuel pressure remains 4-6psi. There are no apparent leaks. I might have expected the pressure to rise a few PSI when the carb bowl and supply piping gets full and the carb stops fuel flow. Presumably the pump might be designed to stall at this point and stop making noise. Mine doesn’t, it appears to continue to run despite hydraulic stall and no flow.
Is this normal behavior?
Peter