How Does the Gas Pump Know When to Stop

Does gas stop pumping automatically?

How do gas pumps know when to stop? Well, it has to do with the way the gas pump works. When you fill your tank with gas, you’re replacing the air that’s in there. “The more gas goes in, the more air must come out,” explains Jake McKenzie, Content Manager at Auto Accessories Garage.

How does a gas pump know to shut itself off?

Normally, air flows through that tube while you’re filling and the gas keeps flowing as long as you hold down on the trigger. When that hole gets covered by gasoline (when your tank is full), a vacuum forms inside the nozzle and an automatic shutoff switch gets tripped, turning off the flow of gas with a thunk.