How does the petrol pump know when my tank is full?

Question

There appears to be some kind of sensor on the pump, but I still can’t understand how it can tell when the tank is full to turn the pump off

In: Engineering

Answer 1

There is a second smaller sensing tube going down along the main fuel filler. This have some small airflow through it from a pump in the handle which again is driven by the fuel flow. When the fuel comes up to this sensing tube it slightly changes the backpressure which will then trigger a mechanical device in the handle that shuts off the fuel flow.