Patent ID: 6862516

Claim:
A fuel gas purge system having failure diagnostic function in an internal combustion engine comprising: a fuel transpiration-preventing device that adsorbs fuel gas produced in a fuel tank into an adsorbent of a canister disposed in the middle of a purge passage communicating the fuel tank to an intake pipe and opens and closes a purge control valve based on operating conditions of the internal combustion engine in order to introduce the adsorbed fuel gas into the intake pipe, thereby preventing transpiration of fuel; plural sensors that detect operating conditions of said internal combustion engine; first malfunction judgment condition detecting means that detects satisfaction of first malfunction judgment conditions of said fuel transpiration-preventing device on the basis of operating condition information from said plural sensors; an atmospheric air port blocking valve that blocks an atmospheric air port disposed on said canister; sealing means that closes both of said purge control valve and said atmospheric air port blocking valve and transforms said fuel transpiration-preventing device into a hermetically sealed section as a whole; integrated purge amount measuring means that measures a integrated purge amount on the basis of an integrated time during which said purge control valve is subject to open control or a purge integrated flow rate based on said open control; second malfunction judgment condition detecting means that detects that second malfunction judgment conditions are satisfied when said first malfunction judgment conditions are satisfied and the integrated purge amount after starting the internal combustion engine is not less than a first predetermined value; a fuel tank internal pressure sensor that detects an internal pressure in said fuel tank; and malfunction detecting means that detects any malfunction in said fuel transpiration-preventing device on the basis of a result detected by said fuel tank internal pressure sensor; wherein, when the detection of malfunction is interrupted after said second malfunction judgment conditions are satisfied, said integrated purge amount is cleared, and the next second malfunction judgment conditions are determined satisfied when said integrated purge amount is not less than a second predetermined value that is shorter than said first predetermined value.