I have a 1992 Buick Century with 195k miles. Many times at the gas pump the nozzle shuts off a few times before the tank is full. Sometimes the attendant ( my state dosen’t allow self-serve ) gets angry and says there’s something wrong with my car. Is it possible that my tank is not properly vented to allow fumes to escape? Is the problem caused by a defective charcoal cannister or some other emmision device?
Yes, those are possibilities. If the attendants have been topping off the gas tank when they fill it they are very good possibilities.
Another possibility is a collapsed filler hose.
As mc wrote, yes your tank is not properly vented. I don’t recall what was common in 1992, but by 2000 they had venting systems that would be damaged if the tank was topped off, then it made it even more difficult to fill.
Look around in the glove box, door frame, under the filler cap and in the owner’s manual. See if it says anything like “Don’t top off the tank when refilling.” If so the attendant likely was the cause of the damage.