a leak check system executes a leak check processing . in the leak check processing , the system closes a canister valve and a purge valve to close the fuel vapor purge system . then , the system detects and monitors a pressure in the fuel vapor purge system . during the leak check processing , the system detects a rapid change of the pressure that is caused by a deformation of a wall of a fuel tank . the system cancels or suspends the processing to avoid erroneous detection of the leak . if the leak check is canceled , the system opens the canister valve to open the fuel vapor purge system .