Finley Atherton
Well Known Member
On two separate, consecutive flights I had some strange fuel pressure readings. 0-320, carb and standard Vans fuel system. Flying along in the cruise and the fuel pressure suddenly climbs from the normal 4 psi to between 10 to 14 psi. The engine continues to run normally and FF remains unchanged. Turning ON the electric boost pump brings the fuel pressure back to around 3 to 4 psi. Everything is normal for a minute or two and the same thing happens again with the boost pump again bringing the fuel pressure back down. This cycle of events is repeated about 5 times after which the fuel pressure returns to normal for the remainder of the flight. I have inspected the fuel system, fuel vents, the engine breather and the connections to the fuel pressure transducer and found nothing abnormal. What I can't understand is why turning the boost pump ON would bring the FP back down to normal The LAME (Australian aircraft engineer) I spoke to said the FP can go up if the vents are partially blocked (I can't really understand why??). I rarely fill the tanks to the very top but I did do this before these two flights. Filling the tanks to the top could have got fuel into the vent lines which could have been like a partial blockage and maybe the boost pump eventually sucked the fuel out of the vent line. This is about the only thing I can think of, but I think it is unlikely.
Anyone got any suggestions?
Fin
9A
Anyone got any suggestions?
Fin
9A