Fuel Pressure Maxed Out

[AlanA]

At runup today my fuel pressure was normal but after an hour or so in cruise at 10,500 it was maxed out to the high side - completely pegged to the right.  It did this once before but then ran normally the next flight.  No effect on the engine, it was purring liking normal.  A search through old posts showed a few others have experienced the same thing. If you have had this problem what was the final fix?  How did you troubleshoot it?  Did you rebuild the pump or install a new transducer, both or neither.   What is the most likely cause, or where would you look first?  What was the cost for the repair.?

 

Thanks in advance for sharing your knowledge and experience

[M016576]

Not sure what type of mooney you have, or what kind of instrumentation, but...

On my J, with the stock gauge, if the ground was loose on that little gauge, the needle would peg to the right. Might want to check that first, and spray it with a little contact cleaner.

If you have 2 gauges showing you problems (pegged fuel pressure, plus surging fuel flow), then you may have a problem

Somewhere. Normally you'll see fuel blockages that cause abnormally high pressure in a few places, though: fuel flow, fuel pressure and higher than normal EGT's for a known mixture setting. Like every good answer regarding airplanes, though... "It depends."

[LAE]

Not sure what type of mooney you have, or what kind of instrumentation, but...

On my J, with the stock gauge, if the ground was loose on that little gauge, the needle would peg to the right. Might want to check that first, and spray it with a little contact cleaner.

If you have 2 gauges showing you problems (pegged fuel pressure, plus surging fuel flow), then you may have a problem

Somewhere. Normally you'll see fuel blockages that cause abnormally high pressure in a few places, though: fuel flow, fuel pressure and higher than normal EGT's for a known mixture setting. Like every good answer regarding airplanes, though... "It depends."

Had the same problem in my J. Broken wire. New connector crimped on and no more problem. Hope yours is an easy, cheap fix as well!

[ALP]

I had a sticking transducer. It would max at startup/runup but come back to zero at shutdown. Changed fuel pump and no change. With a second gauge on the ground was similar. we finally hooked up a airline regulator with second gauge attached and slowly raised pressure to max and back down. Discovered the transducer would stick at max until pressure came down to 20 +/- psi. then the dash gauge would drop and match second gauge.

I replaced transducer. Others have said a little carb cleaner spray in the transducer has loosened them up.

Good luck.

[AmigOne]

Hope you are not looking to buy a new transducer anytime soon, Part# 880045-501 is about $2500.  And while on the subject of crazy prices, a new dual warning horn (stall+gear), part #283 by Safe Flight Instruments is $2461. 

[ALP]

I seem to remember the fuel pressure sending unit being less than $100.00.

[M016576]

Hope you are not looking to buy a new transducer anytime soon, Part# 880045-501 is about $2500. And while on the subject of crazy prices, a new dual warning horn (stall+gear), part #283 by Safe Flight Instruments is $2461.

With that cost, might as well buy an EI CGR-30P for 3200, replace all those little crap gauges and get a fancy 4 place monitor out of the deal.... Just say in'....

[Jeff_S]

Ditto on the faulty gauge problem. There is some weird grounding issue in my panel that occasionally causes the fuel gauge to peg to the right, and sometimes to drop to zero. Usually just pressing it into the panel, or making sure it's screwed in tight, helps solve the problem. I have the JPI backup showing me fuel flow so I've never really worried about it too much...electrical gremlins can chew through your bank account really fast. But I will take the solutions others have shown here and suggest them to my A/P and avionics guy. Thanks.

[AmigOne]

Exactly the same problem with my right fuel gauge, i have the JPI connected to my GPS so always know within 1-2 gls how much fuel I have    

[AlanA]

I am going to try the simple fixes you have recommended.  Regardless if the simple fixes work or not, in addition I've decided the time has come to add a new fuel flow gauge.  After reading many archived posts and finding other comparisons online I am leaning towards EI FP-5L.  I like the added features the EI has over the JP FS-450, however I like the red, double line read out on the JP.  Tough choice.

 

Thanks for your suggestions.