fuel shooting out check valve

[povelocj]

We have run into an issue that we can't solve. During testing fuel has started shooting out of our vent tube and check valve. The line is about a foot and a half long, begin, at the top of our fuel tank (but below the filler neck), and the venting end is located about 6 inches above the top of the filler neck. We have ruled out problems with the check valve, fuel would still come out regardless. We proved that the fuel return is working and returning to the tank. The engine is an f4i and the tune is still a bit rich. Has anyone run into issues like this before? Thanks for any help

[povelocj]

We have run into an issue that we can't solve. During testing fuel has started shooting out of our vent tube and check valve. The line is about a foot and a half long, begin, at the top of our fuel tank (but below the filler neck), and the venting end is located about 6 inches above the top of the filler neck. We have ruled out problems with the check valve, fuel would still come out regardless. We proved that the fuel return is working and returning to the tank. The engine is an f4i and the tune is still a bit rich. Has anyone run into issues like this before? Thanks for any help

[Pete Marsh]

The desity of the fuel reduces quite a lot with increasing temperature, and hence it's volume will increase when you run your car. It sounds like your vent tube will vent from a place on the tank that has liquid covering it, and so fuel will come out of it.
A larger diameter vent hose arranged such that it won't trap liquid, but will trap air, should solve your problem.

Pete

[Drew Price]

I would be tempted to say it's just sloshing, an 18" vent line is far too short in my oppinion, especially since you're venting where the end of the vent is submerged when the tank is full like Pete says.

A lot of teams run the vent line up and over the main roll hoop all the way down to the bottom of the car, you might try that as well, it's easy and cheap.

If the tank is pressurizing for some reason you'll get that too.

I know it's stupid, but double-check that your check valve is oriented so it can suck 'IN' and not blow 'OUT'.