Fuel Filler Cap: Description and Operation

PURPOSE/OPERATION





The relief valve is adopted to prevent the development of vacuum in the Fuel Tank which may occur in case of trouble in the fuel vapor line. In normal condition, the filler pipe is sealed at (A) and at the packing pressed against the filler pipe end. As vacuum develops in the fuel tank, atmospheric pressure forces the spring down to open the valve; consequently air is led into the fuel tank controlling the inside pressure.