Abstract: The present invention provides an evaporated fuel system diagnostic apparatus. The evaporated fuel system diagnostic apparatus includes a malfunction determination unit which determines whether a malfunction occurs in an evaporated fuel system, by introducing a negative pressure of an intake passage into a fuel tank. An operating condition setting unit sets, when the malfunction determination unit has started the introduction of the negative pressure of the intake passage into the fuel tank, an operating condition of an internal combustion engine in a predetermined condition that causes the negative pressure of the intake passage to be within a predetermined pressure range. Further, the present invention provides a vehicle control apparatus for an automotive vehicle equipped with the evaporated fuel system diagnostic apparatus.

Abstract: The present invention provides an evaporated fuel system diagnostic apparatus. The evaporated fuel system diagnostic apparatus includes a malfunction determination unit which determines whether a malfunction occurs in an evaporated fuel system, by introducing a negative pressure of an intake passage into a fuel tank. An operating condition setting unit sets, when the malfunction determination unit has started the introduction of the negative pressure of the intake passage into the fuel tank, an operating condition of an internal combustion engine in a predetermined condition that causes the negative pressure of the intake passage to be within a predetermined pressure range. Further, the present invention provides a vehicle control apparatus for an automotive vehicle equipped with the evaporated fuel system diagnostic apparatus.

Abstract: The present invention provides an evaporated fuel system diagnostic apparatus. The evaporated fuel system diagnostic apparatus includes a malfunction determination unit which determines whether a malfunction occurs in an evaporated fuel system, by introducing a negative pressure of an intake passage into a fuel tank. An operating condition setting unit sets, when the malfunction determination unit has started the introduction of the negative pressure of the intake passage into the fuel tank, an operating condition of an internal combustion engine in a predetermined condition that causes the negative pressure of the intake passage to be within a predetermined pressure range. Further, the present invention provides a vehicle control apparatus for an automotive vehicle equipped with the evaporated fuel system diagnostic apparatus.

Abstract: The present invention provides an evaporated fuel system diagnostic apparatus. The evaporated fuel system diagnostic apparatus includes a malfunction determination unit which determines whether a malfunction occurs in an evaporated fuel system, by introducing a negative pressure of an intake passage into a fuel tank. An operating condition setting unit sets, when the malfunction determination unit has started the introduction of the negative pressure of the intake passage into the fuel tank, an operating condition of an internal combustion engine in a predetermined condition that causes the negative pressure of the intake passage to be within a predetermined pressure range. Further, the present invention provides a vehicle control apparatus for an automotive vehicle equipped with the evaporated fuel system diagnostic apparatus.

Abstract: The present invention provides an evaporated fuel system diagnostic apparatus. The evaporated fuel system diagnostic apparatus includes a malfunction determination unit which determines whether a malfunction occurs in an evaporated fuel system, by introducing a negative pressure of an intake passage into a fuel tank. An operating condition setting unit sets, when the malfunction determination unit has started the introduction of the negative pressure of the intake passage into the fuel tank, an operating condition of an internal combustion engine in a predetermined condition that causes the negative pressure of the intake passage to be within a predetermined pressure range. Further, the present invention provides a vehicle control apparatus for an automotive vehicle equipped with the evaporated fuel system diagnostic apparatus.

Abstract: A diagnostic apparatus for a fuel vapor purge system is provided which includes a pressure sensor that measures a pressure in a fuel tank, and which conducts leak diagnosis of a purge path based on a change in the pressure in the fuel tank and an amount of fuel vapor generated in the fuel tank. The change in the pressure is measured after sealing the purge path while providing a difference between inside pressure and outside pressure of the purge path, and the amount of fuel vapor is measured after applying an atmospheric pressure to the purge path and sealing the purge path. The diagnostic apparatus further detects a predetermined state after starting application of the atmospheric pressure to the purge path, and determines that the purge path has reached an atmospheric pressure state upon. detection of the predetermined state. The amount of fuel vapor generated in the fuel tank is measured when it is determined that the purge path has reached the atmospheric pressure state.

Abstract: A fuel tank is divided into a fuel chamber and an air chamber by a bladder diaphragm. Under a condition that both the amount of intake air Ga and the engine revolution speed NE of an internal combustion engine are kept at constant values, a vapor concentration correction factor FGPG during a fuel injection duration TAU is calculated based on a change in the air-fuel ratio detected when gas is purged from the air chamber toward an intake passage of the engine. Based on the vapor concentration correction factor FGPG, it is determined whether there is fuel leakage from the fuel chamber to the air chamber. With this determination technique, a fluctuation in the air-fuel ratio is not caused by a situation where the engine is in a transitional state, during fuel leakage detection, so that the vapor concentration correction factor FGPG assumes a proper value corresponding to the vapor concentration in the air chamber.

Abstract: A fuel vapor purge system has a canister for adsorbing fuel vapor from a fuel tank, a bypass passage bypassing the canister, and a bypass valve for controlling the state of connection of the bypass passage to a purge passage. The bypass passage is provided with a venturi so that the flow passage resistance of the bypass passage is normally greater than the flow passage resistance of the canister. The amount of flow of gas from an air chamber to an intake passage changes in accordance with the flow passage resistance of the passage. In this case, the tank internal pressure in the air chamber converges to a value corresponding to the flow passage resistance of the passage between the air chamber and the intake passage. Therefore, based on the tank internal pressure occurring before and after the supply of a drive signal to the bypass valve, it is determined whether the bypass passage has a clogged abnormality and whether the bypass valve has a fixation abnormality.

Abstract: A diagnostic apparatus for a fuel vapor purge system is provided which includes a pressure sensor that measures a pressure in a fuel tank, and which conducts leak diagnosis of a purge path based on a change in the pressure in the fuel tank and an amount of fuel vapor generated in the fuel tank. The change in the pressure is measured after sealing the purge path while providing a difference between inside pressure and outside pressure of the purge path, and the amount of fuel vapor is measured after applying an atmospheric pressure to the purge path and sealing the purge path. The diagnostic apparatus further detects a predetermined state after starting application of the atmospheric pressure to the purge path, and determines that the purge path has reached an atmospheric pressure state upon detection of the predetermined state. The amount of fuel vapor generated in the fuel tank is measured when it is determined that the purge path has reached the atmospheric pressure state.