Yesterday I noticed some strange fuel pressure behavior. Fuel pressure before start-up is usually about 42 PSI, 44 when I run the second pump. After start-up it settles down to around 32 with the vacuum driven regulator. Yesterday it was 56, (58 with the second pump) and stayed over 40 after start-up. The engine ran normally and mixture seemed about where it always is. Fuel pressure was over 40 on the run-up, so I taxied back to the hangar. I couldn't find anything obviously wrong with the vacuum to the regulator, so I tried again. Fuel pressure was again in the mid fifties before start-up, but dropped back to normal during the run-up, so I took her up. Everything seemed normal during a half-hour flight. The only thing I can come up with is that I cleaned the filters during the annual and removed a very slight amount of crud from one of them.
I keep thinking the plane is trying to tell me something. Any theories what?
John