There's already a shutoff in the nozzle that prevents overfilling when the level in the tank reaches the end of the nozzle, at least on any pump I've used in th

There's already a shutoff in the nozzle that prevents overfilling when the level in the tank reaches the end of the nozzle, at least on any pump I've used in the past decade. A Leatherman is just about the right size to jam in there and hold the trigger open if the metal clip has been removed.