Patent ID: 7448257

Claim:
A leak check apparatus for an internal combustion engine, the apparatus comprising: a canister having an air inlet opening, the canister temporarily adsorbing fuel vapor produced in a fuel tank; a fuel vapor passage extending from the fuel tank to the canister; purge passage extending from the canister to an intake system of the internal combustion engine; a purge valve for opening and closing the purge passage; a cut valve for opening and closing the air inlet of the canister; and a leak check control unit for checking a fuel vapor leak in a purge line extending from the fuel tank to the purge valve through the canister, the leak check control unit operable to: detect pressure in the purge line; measure a first pressure change rate of the purge line after a predetermined negative pressure is applied to the purge line and the purge valve and cut valve are closed, sealing the purge line at the predetermined negative pressure; measure a second pressure change rate of the purge line after measuring the first pressure change rate, opening the cut valve to expose the purge line to the atmospheric conditions and closing the purge valve and cut valve to seal the purge line at the atmospheric pressure, and after a degree of pressure increase in the purge line exceeds a predetenriined reference pressure; and determine a degree of leak based on a difference between the first pressure change rate and the second pressure change rate.