Your tank is vented, just not by means of any fitting or port or tube on the tank itself. the "tank" end of the vent tube I described previously is actually near the outboard end of the filler neck. Open the trunk and see for yourself. It's up there rather than down at the tank because up there at the top of the filler neck it doesn't usually see liquid fuel -- unless you overfill the tank when it's cool out, then it gets warm out, the gasoline expands, and pushes its way out the vent tube. Make sure that vent tube is present, not crimped or dented shut anywhere along its length, not clogged with debris. That plus Damraider's cap will solve the problem.
