well from just looking at them the kia looks like a 50l and im not sure about the pontiac, but more than likely 80l. if u want a forsure answer then they should be in the manual of the car.
Would be so simple as a vaccuum trouble. Need to verify the breather tube to be certain the tank is venting as you fill. If the breather tube is kinked or blocked the vehicle will “hiccup” with fuel and cause the pump to close off.