Fuel Pressure/RPM changes

LanefourLanefour
in General Discussion
I was flying my Cherokee 140 the other day, when I had a strange occurence. The fuel pressure would rise by a noticable amount, and the RPM would drop slightly, maybe 50-100 RPMs. It wasn't rough, just a small power change. It did this a few more times during the flight, never got worse, but it definitely concerns me. I would certainly expect a power loss/reduction if the fuel flow was REDUCED, but not increased.

I am taking the airplane in to check compressions on the cylinders for excessive oil consumption, and asked the mechanic if he had ever heard of this issue with the fuel pressure/RPM change, and he replied that he had not. Anyone heard of this problem before?

Comments

  • flyguydonflyguydon
    On fuel injected engines, higher pressure will cause an increase in fuel flow to the cylinders making it run a bit richer. On a carb engine like yours, it should really have no effect since your carb has a float and the pressure to the bowl will have no real impact on how much it uses. Unless the pressure is REAL high, it might cause a little turb in the bowl, but really not more than you might get flying in the bumps...

    During hot times of the year, you might be seeing a little vapor lock or similar in the fuel system. This can be made a bit more pronounced if you use auto fuel... and especially if it has any ethanol in it.
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