How does a gas pump know when to stop pumping?
Im not sure but i think this is how it goes. When you pump, whether you pump holding or use the clip, the fuel is filling up the tank and causing pressure. since you can’t pressurize liquid it pressurizes the air in your tank. The air is then pushed down the line to the purge control valve, wicth pushes the air through a charcoal filter, and the gas fumes are gone. Now once the tank is full, and no air is left, the pressure pushing back on the pump will start to build and the pump swicthes off because you can’t put fuel the other way through.
