I just finished an ARF and when I tried to fuel it, I got pressure in the tank. It would take fuel, but if I did not pinch the line, it would spray fuel, with the vent line on and off of the muffler. I took the tank out and out of the plane it seems ok. I made sure there was nothing pinching the lines when in the plane. I even took all of the foam out from the area because I thought that might be causing it but it still did it. This makes no sense to me since this has never happened before with any of the 10 or so ARFs I have built. Any thoughts?

Sure sounds like your vent line is blocked.

Any chance you could have switched the lines around and you are fueling through the vent line? This would build pressure as the only release or venting would be through the needle valve. Been there, done that, afternoon spent getting it right!! DickB

Is this a 2 or 3 line tank?

It sounds like you are using a 2 line fule system. Remove both brass tubes and try to push fuel thru each one of them and you will find that one of the tubes is blocked.........

Absolutely sounds like a two line system. Go with a three line and you will, in my oppinion, be better off. I know people who shy away from this but I never had a problem. John

It is a 2 line tank. I initially thought the vent was blocked, but when I fuel the tank when it is not in the plane, it seems fine. My next thought was that a line was getting folded or something when I put it in, so that is when I took out all of the foam around the tank to see what happened. I made sure the line was open and it still did the same thing. I think I am just going to get a new tank. Thanks for all the help.