We had a Hyundai with the same problem. Every time my nephew fills the tank when he goes to start it he has to gun the engine and it takes several attempts to start. Mechanic changed some fitting but it didn’t do the trick. Only happens after tank is filled. Other than that car runs fine. Only 45k miles.
Stop filling the car when the automatic pump shuts off.
Tell your nephew to stop topping off the tank. It can damage the car. Fill it until the pump clicks off the first time.
This happens even when he only puts a few dollars worth of gas in. (He’s a teenager and rarely fills the tank all the way).
He rarely tops it off. He usually only puts in $20 or $30 dollars at a time.
If you’re sure he’s not overfilling it, have you watched (trained) him on fueling a car? It may seem silly, but could he be just barely sticking the nozzle in and filling the overflow tube?
Of course, you’ve been with him at least once and watched him…just to make sure he’s not doing something obviously incorrect? We all need training sometimes.
Have him loosen the gas cap the next time it happens and see if the problem goes away. If it does, the tank isn’t venting properly.