How do gas pumps know when to stop pumping gas?

This mechanism has been around for a long time, so it is safe to say there is not a miniature camera inside the nozzle hooked to a microprocessor. It's purely mechanical -- and ingenious. Near the tip of the nozzle is a small hole, and a small pipe leads back from the hole into the handle. read more

If it didn't know when to stop, your gas tank would overflow. The gas nozzle has a small pipe running alongside it called a venturi. When the gasoline level rises and the tip of the pipe is lower than the top level of the gas, the air pressure that keeps the gas flowing from the nozzle chokes off and the nozzle handle shuts down, stopping the gas from entering the tank. read more

If you've ever put gas in a car, you'll know that the pump magically knows when to stop spewing fuel into the tank. That's super useful, and safe too. read more

gas pump full tank, gas pumps, nozzle. ­This mechanism has been around for a long time, so it is safe to say there is not a miniature camera inside the nozzle hooked to a microprocessor. read more

A venturi is used to create a vacuum as the gas is being pumped. This vacuum creates suction at the sensing port (shown above). read more