Abstract: A sealing valve 28 that controls a communication state between a fuel tank 10 and a canister 26 is provided. During stop of an internal combustion engine, the sealing valve 28 is generally closed, and the canister 26 is opened to the atmosphere. The sealing valve 28 is opened when the internal combustion engine is stopped, and differential pressure exceeding a valve opening determination value is generated between tank internal pressure and atmospheric pressure. A change in the tank internal pressure generated between before and after the sealing valve 28 is opened is detected. When the change in the tank internal pressure is below a predetermined determination value, closing failure of the sealing valve is determined.

Abstract: A leak check apparatus performs a leak check of a fuel vapor processing apparatus based on a change in a negative pressure in a purge line during leak down. The pressure change during leak down is corrected by measuring an amount of vapor generated after the purge line is opened to the atmosphere. A first pressure change rate of the purge line is measured after a predetermined negative pressure is applied to the purge line, and the purge line is sealed at the negative pressure. A second pressure change rate of the purge line is measured after the first pressure change rate of the purge line is measured, the cut valve is opened to expose the purge line to the atmosphere, and the purge valve and the cut valve are closed to seal the purge line at the atmospheric pressure. The second pressure change rate measurement does not begin until the degree of pressure increase in the purge line exceeds a predetermined reference value.

Abstract: The invention relates to a method for checking the gastightness of a motor vehicle tank ventilation system consisting essentially of a fuel tank, an adsorption filter, a ventilation line with a pressure sensor, a fresh air line with an adsorption filter check valve (AAV), and a regeneration line with a tank ventilation valve (TEV) to the internal combustion engine. To compensate for the outgassing of fuel, the total diagnosis time tD is formed from the negative pressure buildup time t1 and the negative pressure decay time t2 as a measure of the tightness of the tank ventilation system and is compared to a corresponding diagnosis time threshold tDS.

Abstract: An evaporative fuel treatment system is disclosed that includes a canister, a detection passage having a reduced area portion, and switching device that switches fluid communication. Also included is a depressurizing device for depressurizing the detection passage coupled to the detection passage on a side of the reduced area portion opposite to the switching device, and a pressure detecting device. Moreover, the system includes an evaporative fuel state calculating device for calculating an evaporative fuel state in the mixture based on a cutoff pressure, an air pressure, and a mixture pressure of a mixture of air and the evaporative fuel. In one embodiment, the cutoff pressure, the air pressure, and the mixture pressure are detected independently and discontinuously. In another embodiment, the cutoff pressure and the air pressure are detected on a continual basis during purge of the evaporative fuel.