[K5Fan]

It's based on the pressure that the gas station pump feels. There is some kind of valve or diaphragm in the pump handle. I don't know about 2004s but newer vehicles have some kind of sensor in the vent or ecco system. When that goes bad somehow it tells the pump that the tank is full.

When it pukes gas before the pump shuts off, I wonder if that would have something to do with too much ventilation? When you fill up a 5 gallon tank, the pump shuts off, but only when the gas reaches the end of the nozzle. Maybe today's gas pumps are set to sense a higher pressure? When your tank shows that it is full, from what I understand, the tank is only about 80% full, right?

My 70 K5 drinks so much gas that one time I left it running when I was filling it up, and the pump never stopped pumping!!

Chris.