Strange Fuel Pressure Issue

[Joe Larussa]

So yesterday I went to start my engine. As always, I flip my EI digital fuel gauge to pressure as I prime. Normally I see around 23 PSI, but today it's only around 19.

I start the engine to see what happens. Starts normal, but fuel pressure still low. I figure let's run it up and see what happens. At run up it's now around 20, which is still in

operating range, but not what I usually see. I turn on the boost pump and it hits around 22, so I decide I'll take off and be prepared to abort if I don't like what I see. Pressure

increases to 23 so I take off. Flew a downwind departure and watched it increase to 24.4, so I turned off the boost on downwind ready to turn base if it quit. After that all was back

to normal. Any thoughts? EI gauge was installed about two years ago. Thanks in advance!

[N201MKTurbo]

What is your normal fuel pressure with the engine driven pump and the boost pump?

It would be unusual for them both to fail at the same time.

It seems like the common element is the sensor.

It would take a substantial leak to cause that much pressure drop. 

[Joe Larussa]

Normal pressure is around 23 when I hit the boost for priming. Over 25 when on take off roll.

I was thinking a clog somewhere? It did finally come back to normal.

Edited September 20, 2021 by Joe Larussa
misspelling

[Joe Larussa]

Today I opened up and checked the servo screen as well as the screen aft the electric fuel pump for any serial numbers. Clean as a whistle, not one spec of anything.

[Mooney Dog]

I would think pump or fuel tank vent would be the other causes here. Temp might have some play in this as well. 

[Guest]

You might consider pulling the fuel pressure fitting from the fuel servo and checking the restrictor hole.

Clarence

[Joe Larussa]

Just to follow up. Detached the fuel pressure hose from the pressure sensor and as far I could tell, looks like there was a little fuel lube goop in there. Cleaned it all up and everything appears to be back to normal.