Patent ID: 7117729

Claim:
A diagnosis apparatus for a fuel vapor purge system which traps the fuel vapor generated in a fuel tank to a canister, to purge the fuel vapor trapped to said canister to an intake passage of an internal combustion engine, comprising: a pressure generator forcibly changing a pressure in a shielded purge passage inclusive of said fuel tank; a pressure detector detecting the pressure in said purge passage; and a diagnosis device forcibly changing the pressure in said purge passage by said pressure generator and also receiving a detection signal from said pressure detector, to diagnose whether or not the leakage occurs in said purge passage, wherein said diagnosis device starts the diagnosis processing from a standby period that has elapsed after an operation of said internal combustion engine was stopped, and wherein said diagnosis device calculates a standby time defining the standby period when said internal combustion engine has been stopped, and starts said diagnosis processing from said standby time that has elapsed after the operation of said internal combustion engine was stopped.