with the application of a knife blade,the end of the valve can be removed,at least those on my two cars can,the only way I have found to remove and replace the complete valve is to cut the plastic pipe and replace by making a bridge with rubber hose and a couple of hose clips,be generous with the length,get plenty of plastic hose into the rubber one,the return valve should have a spring to hold the valve against the pipe to prevent it draining back into the tank,a missing or broken spring will allow the valve to seal the pipe under pressure,resulting in over fueling