A valve system includes features to control flow of fuel between a pair of fuel tanks during a transfer operation so as to prevent flow of return fuel from a carburetor back to a previously filled tank. The valve system includes a pair of valve bodies each having two mechanically operated sealing elements therein. One of the valve bodies has larger inlet and outlet ports to control the supply of fuel from the source tank of the system to a vehicle carburetor. The other of the valve bodies has smaller ports to control the flow of excess fuel flow to the selected source tank of the pair of tanks during engine operation. Each of the valve bodies includes a push rod operatively connected to a single motor drive yoke element. Each sealing element is spring biased and has an insert directed therethrough constituting a seal carrier slidably supported on the push rod.