[Cashburn]

Your tank by design is vented through the gas cap. But that will not cause a fuel smell while driving. More than likely you have a small (or several) leak along your fuel line (perhaps even the return) that is misting when you are running and it is minor enough that it will not puddle or drip, but rather evaporate.

You need to run your hands along the whole system of hoses and fittings.