I've been smelling gas in my Sahara for a couple years now. I know it''s not the gas cap, but that can be one cause. Some other things are the sending unit gasket and the filler neck. I'm pretty sure that mine is one of the latter two, but I haven't wanted to drop tank. It's sort of a pain, but not that bad. Change that gas cap and if that doesn't fix you up, I'd start looking in those other areas.