>All fuel tanks have a vent valve to redirect vapours from the fuel. During a fillup the turbulent flow of the fuel causes quite a build-up of vapours that need

>All fuel tanks have a vent valve to redirect vapours from the fuel. During a fillup the turbulent flow of the fuel causes quite a build-up of vapours that need to be redirected. vented fuel tanks began in the 60s. Many older cars have absolutely no vent valve to speak of -- the vapor is dumped from the fuel cap, which acts as a vent; meaning the vent isn't present during fill-up on this style of design.