Patent ID: 8813726

Claim:
A fuel tank system comprising: a fuel tank for holding fuel; a canister capable of adsorbing fuel vapor inside the fuel tank and releasing the fuel vapor; a gas separator that separates air components from gases in the fuel tank and discharges the separated air components externally to the fuel tank; an internal pressure detecting device for detecting internal pressure of the fuel tank; and an electronic control unit configured to control a switching device to switch between a first state in which the internal pressure of the fuel tank is in a negative pressure state of a negative pressure of a first specific value or lower and in which first state fuel vapor that has been adsorbed by the canister is suctioned into the fuel tank by the negative pressure, and a second state in which the internal pressure of the fuel tank is in a positive pressure state of a positive pressure of a second specific value or higher and in which second state gas of a gas layer is caused to pass through the gas separator and air components in the gas layer are caused to be externally discharged from the gas separator by the positive pressure, at a time of not supplying fuel to the fuel tank.