Hi, Perry....One question....Does your unburned fuel (from the fuel rail) go back into your sump tank also?   Or do you return the unused fuel to one of your fuel tanks?  If I were returning fuel to one of the main tanks, I would think that venting the sump would be appropriate, but since I am sending fuel undere pressure back into the sump tank, I am concerned that once the sump tank is full, the additional fuel pumped back into the sump tank would take the path of least resistance....out the vent instead of back up the fuel line into the tank?   Thanks for your input.  Paul Conner

I have the stock Long-EZ fuel system, lines from the main tank run forward to the fuel selector valve in the cockpit. The selected main runs back to the sump tank. I have two Mazda HP pumps inside the sump tank. Fuel return from the fuel rail is to the sump tank.

Fuel does not go out the sump tank vent, because the main tanks are vented as well, and the whole system will tend to seek a common level.

Perry