The Simple Yet Clever Way Gas Pump Handles Shut Themselves Off – SlashGear

Gas pumps are not quite universal. Some models have a switch the user must activate after removing it from the dispenser, while this is an automatic process with others. Those who don’t always fill their tanks to full may not really have registered it, but the pump is not designed to simply dispense until overfilling. This is important to know for those who prioritize a vehicle’s full-tank range.

To prevent this, a venturi tube, parallel to the main tube of the pump, stops the gas. The pump is reliant on air pressure, and that very pressure is cut when the flow reaches and fills the venturi. With a venturi simply amounting to a short length of tubing with an element that regulates the fluid flow, it’s a surprisingly low-tech solution to a potentially very troublesome issue.

This mechanism, however, isn’t infallible. There’s a bit of an art to pumping gas, and that’s because an irregular flow can cause this mechanism to activate before the customer is finished. It’s crucial that little tube is there, though, because filling beyond capacity risks harm to the Evaporative Emission System, which is there to regulate the remnants of a vehicle’s gas.