Abstract: A failure diagnostic system reduces the internal pressure of a fuel tank to a predetermined negative pressure, seals off the fuel tank from the air, and then determines whether an evaporated fuel processing system has failed or not by monitoring an increase in pressure in the fuel tank. In determination, the failure diagnostic system compares a detected pressure in the fuel tank with a reference value that is increased by a predetermined rate. The failure diagnostic system stops update of the detected pressure if the detected pressure becomes higher than the reference value, and resumes update of the detected pressure if the detected pressure becomes lower than the reference value. It is therefore possible to accurately determine whether the evaporated fuel processing system has failed or not even if the pressure in the fuel tank is rapidly increased.

Abstract: There is provided a failure diagnostic system of an evaporated fuel processing system, which comprises a first failure diagnostic device that shuts off an evaporated fuel purge passage connecting a fuel tank and an engine intake passage from the air and determines whether there is any leakage from a large hole by monitoring the degree of increase in pressure in the fuel tank in which engine intake negative pressure is introduced; and a second failure diagnostic device that reduces a pressure the fuel tank to a predetermined negative pressure and seals off the fuel tank from the air to carry out failure diagnosis as to whether there is any leakage from a small hole by monitoring the degree of increase in pressure in the fuel tank. An operating range of the second failure diagnostic device is set to substantially include an operating range of the first failure diagnostic device and to be extended from the operating range of the first failure diagnostic device to include a lower intake negative pressure range.

Abstract: There is provided a failure diagnostic system that reduces the internal pressure of a fuel tank to a predetermined negative pressure, seals off the fuel tank from the air, and then determines whether an evaporated fuel processing system has failed or not by monitoring an increase in pressure in the fuel tank. In determination, the failure diagnostic system compares a detected pressure in the fuel tank with a reference value that is increased by a predetermined rate. The failure diagnostic system stops update of the detected pressure if the detected pressure has become higher than the reference value, and resumes update of the detected pressure if the detected pressure has become lower than the reference value. It is therefore possible to accurately determine whether the evaporated fuel processing system has failed or not even if the pressure in the fuel tank is rapidly increased.

Abstract: There is provided a failure diagnostic system of an evaporated fuel processing system, which comprises a first failure diagnostic device that shuts off an evaporated fuel purge passage connecting a fuel tank and an engine intake passage from the air and determines whether there is any leakage from a large hole by monitoring the degree of increase in pressure in the fuel tank in which engine intake negative pressure is introduced; and a second failure diagnostic device that reduces a pressure in the fuel tank to a predetermined negative pressure and seals off the fuel tank from the air to carry out failure diagnosis as to whether there is any leakage from a small hole by monitoring the degree of increase in pressure in the fuel tank.

Abstract: A fuel evaporative emission treatment system includes a canister which has an evaporative fuel introduction part arranged for communication with a fuel tank, an evaporative fuel emission part arranged for communication with an intake system of an engine, and a vent part arranged for communication with the atmosphere, and which absorbs the evaporative fuel. The fuel evaporative emission treatment system includes a vent pipe having a first passage communicating to the vent part of the canister and to the atmosphere, a first solenoid valve for opening and closing the first passage, an air filter for cleaning atmospheric air flowing thereinto, the filter being provided on the first passage on the side remote from the canister with respect to the first solenoid valve, and a one-way valve or lead valve which defines a second passage communicating to the vent part of the canister. The valve is opened at fueling.

Abstract: The fuel storage system includes a control valve having a valve body which is movable along the inner circumferential wall surface of a filler pipe and which defines a passage isolated from the inner space of the filler pipe. A fuel tank and a canister communicate with each other via a main vapor line. When a fuel cap is attached to the filler port of the filler pipe, the valve body of the control valve is pushed by the fuel cap to be shifted away from the filler port, whereby a first sub-vapor line extending between the fuel tank and the control valve via the passage defined by the valve body is communicated to a second sub-vapor line extending between the control valve and the middle part of the main vapor line, permitting evaporative fuel gas to be introduced from the fuel tank into the canister.

Abstract: A fuel evaporative emission treatment system installed in an engine fuel system has a canister for adsorbing evaporative fuel, a vent hose connecting a fuel tank and the canister, and a vent circulation hose connecting the vent hose and a filler neck of the fuel tank, and the sectional areas of the vent hose and vent circulation hose are set so that the ratio thereof may be a proper value. The negative pressure produced in the filler neck due to aspiration induced by refueling is canceled out by the pressure of fuel gas circulated to the filler neck through the vent circulation hose, whereby the internal pressure of the filler neck is controlled to a value appropriately smaller than the atmospheric pressure. Thus, inflow of the outside air into the filler neck, and thus generation of evaporative fuel gas, can be suppressed, and also the outflow of evaporative fuel gas from the filler neck is suppressed.