Low Fuel Pressure

GPariza · #1 06-15-2007, 05:34 PM

I just returned from a cross country from Dallas to my home field in Florida in my RV6A with a 320. Crusing at 9,000' ; 2400 RPM from time to time the fuel pressure would dip to 1 psi, I tried to trouble shoot and could get the pressure back up by either turning the elect fuel pump on or richen the mixture. Oddly enough, and it may be my imagination but an hr our so later when the tanks were about 1/2 full the presure was about 5psi and leaned. I've spoken to others that have seen the same issue; unfortunatley no one knows why. I've checked the vents and found no obstruction. All suggestions are appreciated.

George Pariza
N242LP

Yukon · #2 06-15-2007, 05:42 PM

Sender malfunctioning. Check wiring, grounds, replace sender.

gasman · #3 06-15-2007, 05:51 PM

Quote:

Originally Posted by GPariza

from time to time the fuel pressure would dip to 1 psi, I tried to trouble shoot and could get the pressure back up by either turning the elect fuel pump on or richen the mixture. Oddly enough, and it may be my imagination but an hr our so later when the tanks were about 1/2 full the presure was about 5psi and leaned. I've spoken to others that have seen the same issue; unfortunatley no one knows why. I've checked the vents and found no obstruction. All suggestions are appreciated.

George Pariza
N242LP

First, Is it a Vans gauge? Check all wire connections incl. grounds. They must be all good and tight. I solder mine. A loose connection will change the reading of the gauge, any gauge that has a sender. Don't just ground to the airframe. Run the grounds back to the battery by way of a ground strip.
Grounds that go from gauge to gauge to gauge..etc etc. like you might do when installing vans gauges, will add up resistance at each connection, and degrade the reading of the gauge........

Good luck! Let us know what you find so we all can learn.

Warren

Bob Axsom · #4 06-15-2007, 08:10 PM

I guess running the fuel line into the cockpit direct pressure gauge wasn't such a bad idea. Really, if the pressure comes back up when you turn on the aux. pump that says to me that your indicated drop in pressure is real, not a gauge problem.

Bob Axsom

gasman · #5 06-15-2007, 08:25 PM

Quote:

Originally Posted by Bob Axsom

I guess running the fuel line into the cockpit direct pressure gauge wasn't such a bad idea. Really, if the pressure comes back up when you turn on the aux. pump that says to me that your indicated drop in pressure is real, not a gauge problem.

Bob Axsom

Just might be some trash in the electric pump

But he will NEVER have fuel leaking on his leg...........

N24YW · #6 06-15-2007, 08:58 PM

Is your fuel pressure sender mounted on the fire wall or the fuel pump? If it is mounted to the fuel pump it will shake a part and be in accurate after some time. I moved mine back to the fire wall and it works great now

Jim Knight
Burlington Iowa
RV6

GPariza · #7 06-16-2007, 05:23 PM

Probably should have mentioned I have a UBG - 16, I took a flight today and pressure was just fine

airguy · #8 06-16-2007, 06:00 PM

Possible vapor bubble formation in the suction line to the pump, resulting in poor total fuel flow? At 9k that could be an issue with heat-soaked fuel, and after a while at altitude as the fuel cools in the slipstream, vapor pressure would come down and the suction line feeding the pump would be bubble free and able to pump out more pressure.