Wouldn’t the owner be able to continue to fill though? I mean by manipulating the pump and nozzle to continue to keep it turned off on, even though it would normally automatically shut off if left alone?
This assumes that the owner does not try to add more fuel after the pump nozzle shuts off the first time. You can still add more fuel if you keep clicking the nozzle and this is what I am trying to discourage. If you add every last drop of gas that you can squeeze into the tank by clicking the nozzle 15 or 20 times and you do that in the summer around here where the air temp is near 100, but the gas comes out of the ground at around 58 degrees, and then let it sit in the sun for awhile, the gas will expand to take up most if not all the head space. Now you go driving down the road and the surface of the gas creates waves that some of which get into the vent lines before the rollover valve can react, you can have this problem and it does occur on post 1996 vehicles.
If you stop on the first click of the nozzle, the system will work exactly as designed and you will never get a P0446 for this reason. The P0446 will be for something else, like a stuck purge valve or clogged vent.
That would be a lesson for the person pumping the gas but a failure in design for the manufacture.
The fuel tank fill tube extends 3 to 4 inches below the top of the tank, the over-fill control valve prevents that space from being filled with gasoline. If the fill nozzle is pulled back so it does not shut off from the gasoline in the fill neck, the fill neck can be filled to the top but the vapor space in the tank can’t be filled with gasoline.
Basic understanding of the fuel system is required for those interested in obtaining an emission inspectors license or for passing an ASE test, professional technicians don’t accuse customers of damaging their fuel systems for simple failures like a failed vent control valve.
Isn’t that identical to what @Tester is saying above?
i.e. Tester: “Since 1996(OBDII) , you cannot over fill a gas tank where it damages the EVAP system”