Quote Originally Posted by njones View Post
We just picked up a new Pipistrel Virus SW from Moriarty NM, 6 hours on the hobbs. 3 hours into the trip to Canada we noticed low fuel pressure - 0.05-0.08 bar showing on the Dynon @ 5200 rpm, 0.1 at 4800 rpm. We diverted to Pampa TX to look into it - on descent into Pampa (idle) we saw the pressure back up to about 0.3 bar (right in the middle of the "ok" range" 0.15-0.40).

I think the possible causes are: a) bad pressure sender b) restricted fuel filter (?) c) bad fuel pump.

We got a fuel pressure gauge from an auto parts place and the plan tomorrow morning is to tee it in to the line beside the sender and verify the pressure reading both at idle and during run-up. That should narrow it down to (a) or (b/c). Then we can insert it before/after the fuel filter to check for any restricted flow there.

As far as I know this installation does not have a boost pump - it's gravity fed from the wings to a gascolator low on the firewall then to the engine-driven pump. This is a factory-new plane.

Any suggestions, advice or help (Rotax Mechanics in the area?) is greatly appreciated.

Nick
I am struggling with the same issue and I think I may have found the answer:

I have a low wing RV-8. The pressure starts out ok and gets lower as time goes on.

I discovered that the tank air vent nut is loose on the inside of the tank. The tank is not re-pressurizing as fuel is removed. When I fix this I'm hoping the low pressure issue goes away.

To check this, I attached a flexible tube tot he tank vent input, put my fingers on the tank vent exit which is inside the tank near the gas cap. When I blew air through the tube, I felt both air and gas.

I then put my ear on the wing right over the point where the tank vent fittings through the tank wall are located. As I blew air into the vent I could plainly hear lots of lovely bubbles being made.

Also, if your vents are clogged, you'll get the same result.