Gas / petrol tank filling issues? How a auto shut off nozzle works.

[TJ Hopland]

Some people have had issues with auto shut off gas / petrol nozzles shutting off when trying to fill their tanks that has sometimes lead to side discussions about how the nozzles work.   Just today a popular Youtuber Steve Mould posted a really good video explaining on exactly how they work.

https://www.youtube.com/watch?v=fT2KhJ8W-Kg

Short version there is a small hole at the end of the nozzle, sometimes its in the end other times its around the edge.  As long as that hole is able to suck mostly air the valve can remain open. Once that hole starts sucking mostly fuel presumably because the level has reached that point in the tank or neck it closes the valve.

This all make sense that they work similarly with a filler neck as they do with a tank where you can actually have the nozzle well into the tank.   Also makes sense why sometimes rotating or holding the nozzle at a different angle helps, its positioning that hole so its not getting a direct splash within the neck.