High Fuel Pressure, Carb Eng, Idle Only

AtomicDog · #1 07-13-2018, 05:28 PM

Should I be worried? Is this a sign of a failing fuel pump? Lycoming has a max fuel pressure of 8 psi for carb engine. My EFIS alarm goes of at idle because fuel pressure briefly raises to 8.3 psi. This is without the electric pump on. Has anyone else had this issue. This has happened several time, it is only momentary and only happens at low rpms. Hmmmmm

blueflyer · #2 07-14-2018, 07:20 AM

Do you think you have an intermittent ground somewhere? I would tend to think not because it doesn't happen while at cruise power.

blueflyer · #3 07-15-2018, 12:57 PM

Larry, i am very curious about this. Please post an update as to what you found to be the culprit.

AtomicDog · #4 07-15-2018, 01:43 PM

I will do some more testing tomorrow. Also of note, at hi cruise 2400 rpm the fuel pressure is 7.2psi. I think it should be no higher than 3psi. Hmmmmm.

YellowJacket RV9 · #5 07-15-2018, 02:33 PM

Happened to me, and also caused carb to overflow, creating a dangerous situation. Installed a new pump and also rebuilt the carb and all is perfect again.

Chris

AtomicDog · #6 07-18-2018, 07:53 AM

I have eliminated the gauge and pressure sender, as the elec. boost pump reads 4.5 psi.
Checked and cleaned the gascolater and carb finger screen, no debris or blockage. Checked the archive and this seem to happen on engines that have set for over a year. Mine had set for 10 years. Lycoming suggest replacing fuel pump every 10 years. So i guess i will bite the bullet and purchase a overhauled pump. Will post the results.

Tom @ N269CP · #7 08-16-2018, 03:09 PM

Quote:

Originally Posted by AtomicDog

I have eliminated the gauge and pressure sender, as the elec. boost pump reads 4.5 psi.
Checked and cleaned the gascolater and carb finger screen, no debris or blockage. Checked the archive and this seem to happen on engines that have set for over a year. Mine had set for 10 years. Lycoming suggest replacing fuel pump every 10 years. So i guess i will bite the bullet and purchase a overhauled pump. Will post the results.

This recently happened to me. But I'd been flying the plane regularly. But the pump was well past the suggested 10 year replacement interval. I have been getting oil droplets accumulating on the heads of the lower bolt heads. Fired it up the other day and the pressure went straight to 8-9 psi at idle...high pressure remained at 2000 rpm, so did not fly it.

I've ordered a new pump & gauge and should have them installed next week.

Seems a lot of these accessories start failing after 15 years in service. To be expected, I suppose.