Abstract: A leak diagnostic apparatus for a vaporized fuel processing system that purges vaporized fuel in a fuel tank of a vehicle is disclosed. The leak diagnostic apparatus comprises a leak diagnostic device, a fuel tank condition detection device and a determining device. The leak diagnostic device carries out a leak diagnosis of the vaporized fuel processing system while the engine is operating. The fuel tank condition detection device detects the conditions in the fuel tank. The determining device determines whether the leak diagnosis should be carried out based on predetermined conditions in the fuel tank.

Abstract: A fuel vapor purge system is configured to execute a highly accurate leak diagnosis with respect to a fuel vapor leak. After the engine is stopped, the temperature of the fuel vapor rises temporarily and then decreases until it reaches the outside ambient temperature. During this period, the purge line is closed off and a purge line pressure decreasing rate is detected when the purge line pressure is slightly above atmospheric pressure. The detected purge line pressure decreasing rate is then compared to a threshold value. The purge system is diagnosed as “normal” if the purge line pressure decreasing rate is equal to or larger than the threshold value and as “leaking” if the purge line pressure decreasing rate is less than the threshold value.

Abstract: A fuel vapor purge system is configured to execute a highly accurate leak diagnosis with respect to a fuel vapor leak. After the engine is stopped, the temperature of the fuel vapor rises temporarily and then decreases until it reaches the outside ambient temperature. During this period, the purge line is closed off and a minimum value reached by the purge line pressure is detected. The difference between the minimum value of the purge line pressure and the atmospheric pressure is compared to a threshold value. The purge system is diagnosed as “normal” if the difference is equal to or larger than the threshold value and a “leaking” if the difference is less than the threshold value.

Abstract: Disclosed is a leak detecting device for a fuel vapor treatment unit that purges a vapor gas generated through evaporation of fuel in a fuel tank (2) into an intake system (22) of an engine (21). The leak detecting device includes a valve (5) that can selectively seal the fuel vapor treatment unit; a pressure detecting sensor (8) that detects a pressure in the fuel vapor treatment unit; and a controller (10). The controller (10) is programmed to: issue a command to close the valve (5) with a view to sealing the fuel vapor treatment unit during stoppage of the engine (21); calculate deviation amounts (P?P0) of the detected pressures during stoppage of the engine (21) after the fuel vapor treatment unit has been sealed; integrate absolute values (|P?P0|) of the deviation amounts, and determine, based on an integrated value (s), whether or not there is a leak occurring in the fuel vapor treatment unit.

Abstract: A leak diagnostic apparatus for a vaporized fuel processing system that purges vaporized fuel in a fuel tank of a vehicle is disclosed. The leak diagnostic apparatus comprises a leak diagnostic device, a fuel tank condition detection device and a determining device. The leak diagnostic device carries out a leak diagnosis of the vaporized fuel processing system while the engine is operating. The fuel tank condition detection device detects the conditions in the fuel tank. The determining device determines whether the leak diagnosis should be carried out based on predetermined conditions in the fuel tank.

Abstract: A fuel vapor purge system is configured to execute a highly accurate leak diagnosis with respect to a fuel vapor leak. After the engine is stopped, the temperature of the fuel vapor rises temporarily and then decreases until it reaches the outside ambient temperature. During this period, the purge line is closed off and a purge line pressure decreasing rate is detected when the purge line pressure is slightly above atmospheric pressure. The detected purge line pressure decreasing rate is then compared to a threshold value. The purge system is diagnosed as “normal” if the purge line pressure decreasing rate is equal to or larger than the threshold value and as “leaking” if the purge line pressure decreasing rate is less than the threshold value.

Abstract: A fuel vapor purge system is configured to execute a highly accurate leak diagnosis with respect to a fuel vapor leak. After the engine is stopped, the temperature of the fuel vapor rises temporarily and then decreases until it reaches the outside ambient temperature. During this period, the purge line is closed off and a minimum value reached by the purge line pressure is detected. The difference between the minimum value of the purge line pressure and the atmospheric pressure is compared to a threshold value. The purge system is diagnosed as “normal” if the difference is equal to or larger than the threshold value and a “leaking” if the difference is less than the threshold value.

Abstract: Disclosed is a leak detecting device for a fuel vapor treatment unit that purges a vapor gas generated through evaporation of fuel in a fuel tank (2) into an intake system (22) of an engine (21). The leak detecting device includes a valve (5) that can selectively seal the fuel vapor treatment unit; a pressure detecting sensor (8) that detects a pressure in the fuel vapor treatment unit; and a controller (10). The controller (10) is programmed to: issue a command to close the valve (5) with a view to sealing the fuel vapor treatment unit during stoppage of the engine (21); calculate deviation amounts (P-P0) of the detected pressures during stoppage of the engine (21) after the fuel vapor treatment unit has been sealed; integrate absolute values (|P-P0|) of the deviation amounts, and determine, based on an integrated value (s), whether or not there is a leak occurring in the fuel vapor treatment unit.

Abstract: Fuel vapor in a fuel tank (1) is purged into an intake passage (8) of an engine (10) through a purge vent (2, 4, 6). The controller (21) determines whether a leak is present in a purge vent from the fuel tank (1) to a purge control valve (11). The determination process comprises a pull-down process in which a pressure in the purge vent is reduced using a negative pressure in the intake passage (8) and a leak-down process of sealing the purge vent at the reduced pressure and monitoring the pressure variation. The controller (21) calculates an error equivalence amount (DVPII), a pressure component corresponding to sloshing in the fuel tank (1) during the leak-down process, and determines the presence of a leak in a highly accurate manner based a corrected pressure (DVP5A) in which the monitored pressure variation is corrected using the error equivalence amount (DVPII) (S22).

Abstract: Fuel vapor in a fuel tank (1) is purged into an intake passage (8) of an engine (10) through a purge vent (2, 4, 6). The controller (21) determines whether a leak is present in a purge vent from the fuel tank (1) to a purge control valve (11). The determination process comprises a pull-down process in which a pressure in the purge vent is reduced using a negative pressure in the intake passage (8) and a leak-down process of sealing the purge vent at the reduced pressure and monitoring the pressure variation. The controller (21) calculates an error equivalence amount (DVPII), a pressure component corresponding to sloshing in the fuel tank (1) during the leak-down process, and determines the presence of a leak in a highly accurate manner based a corrected pressure (DVP5A) in which the monitored pressure variation is corrected using the error equivalence amount (DVPII) (S22).