Patent ID: 7347194

Claim:
A leak diagnosis device comprising: a diagnosing device for performing leak diagnosis of determining whether a leak hole is formed in a purge device, which adsorbs fuel vapor generated in a fuel tank with an adsorbent in a canister and purges the fuel vapor adsorbed by the adsorbent into an intake passage of an internal combustion engine; a state sensing device, when the fuel vapor adsorbed by the adsorbent separates from the adsorbent and produces a mixture gas, for sensing a state of the fuel vapor in the mixture gas; and a period calculating device for causing the state sensing device to perform the state sensing multiple times from a period in which the pressure in the purge device increases due to generation of the fuel vapor after an operation of the engine is stopped and for calculating a state stabilization period in which a change of the fuel vapor state becomes equal to or less than a reference value based on the result of the multiple times of the state sensing, wherein the diagnosing device performs the leak diagnosis in the state stabilization period calculated by the period calculating device.