Fuel pressure gauge fluctuations

Fuel pressure gauge fluctuations

Piper Archer  181 has fuel gauge fluctuations of approx + and - 15 degrees when running on either mechanical or electric boost fuel pump. With engine running only.
If electric fuel pump is turned on with engine stopped readings are steady
Occurs regardless of which or if both pumps ore used. Fluctuations diminish as rpm is increased and engine performance is good under all conditions.
Thought it might be a mechanical fuel pump issue. Any ideas ?

apaquette1@cox.net
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Re: Fuel pressure gauge fluctuations

Hi and thanks for writing.  This is an interesting question.  Please stand by while I forward this to our association A&P Erich Rempert.

Scott Sherer
N344TB - Piper Seneca
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ssherer@wi.rr.com
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Re: Fuel pressure gauge fluctuations

Here's a response from our A&P Erich Rempert:

I assume we are talking fuel pressure...? Sounds like it could be a stickyneedle and seat?

With engine running fuel unused out of the fuel bowl thus requiring fuel to enter and exit, a sticky or malfunctioning needle valve could be jerky in operation and causing the fluctuations you see.

Boost pump with the engine not running will fill up the bowl close the albicans become static.

Engine will run fine as long as there's fuel in the carb, it doesn't know what's going on in regard to supply pressure.

On a car I'd suggest fuel system cleaner, or pulling the assembly out abd cleaning it and trying it again.

If you feel the carb is in good shape it may be the mechanical fuel pump.

-Erich

Scott Sherer
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