Gas tank overflows when filling

I set the pump on autofill and walk away.

Illegal in most places and unsafe in all. When you are pumping gas, do not leave the pump! Yea, it happens, I use to live across the street from a station and I remember two fires. Lucky only one minor injury, but the possibility of more.

Are you in the habit of topping off the tank when you “fill” it? If so that is likely the problem. Your vent system (vapor recovery) may be damaged because you have topped it off one too many times.