Quote Originally Posted by rspears View Post
Contraction is not your problem, as it's sucking air into the tank to replace fuel burned, or due to decreasing vapor pressure due to cooling. Expansion (or a leak) is what causes the fumes. That vent has to work both ways, so a check valve may seem to fix your problem but is going to pressurize your tank with increasing vapor pressures, especially in the summer. Dave (IC2) already shared his experience in your earlier post, including the fact that the charcoal canister doesn't work for a vented system, and his solution, which was a coil of tubing in the vent routing. Seems to me you have the answer, or at least one that worked for Dave.
I have a coil of tubing in my vent line just above my tank, that doesn't seem to help. Someone on the H.A.M.B. suggested attaching a fuel filter w/1/4" fittings to the vent line so the tank could breath. That seems to help, but it's not the cure all.
It was also suggested to run a vent line as high above the tank as I could and create a 180 then back down, kind of like a upside down J trap. I don't see how that would make any difference.
Again, the fuel filter on the end of the vent line does seem to help!
ANY OTHER IDEAS?????