How Do Gas Pumps Know When to Stop

What triggers gas pump to stop?

The gas pump nozzle shuts off due to the way it is designed. When the nozzle shuts off as you’re trying to use it, this does not necessarily mean that it is malfunctioning. Actually, it has a mechanism that is supposed to shut off the fuel supply for safety reasons.

Do gas pumps automatically stop when tank is full?

As long as the tank is not completely full, air flows unimpeded up into the handle, and nothing much happens except that fuel continues to pour into your car. As your gas tank fills, the fuel level rises until it covers the hole at the end of the nozzle.