Apparatus for detecting leakage in an evaporated fuel processing system

A method for determining leakage in an evaporated fuel processing system, the evaporated fuel processing system extending from a fuel tank through a canister to a purge passage through which evaporated fuel from the fuel tank is purged to an intake manifold of an engine, the canister comprising a vent-shut valve that communicates with the atmosphere, comprising the steps of:

• detecting a pressure of the evaporated fuel processing system;
• detecting a stop of the engine;
• closing the vent-shut valve to close the evaporated fuel processing system after the stop of the engine is detected;
• determining whether the evaporated fuel processing system has leakage after the evaporated fuel processing system is closed based on the detected pressure and a predetermined determination value;
• and
• prohibiting the leakage determination if the detected pressure is not within a predetermined range.

A computer program stored on a computer readable medium for use in determining leakage in an evaporated fuel processing system, the evaporated fuel processing system extending from a fuel tank through a canister to a purge passage through which evaporated fuel from the fuel tank is purged to an intake manifold of an engine, the canister comprising a vent-shut valve that communicates with the atmosphere, the computer program comprising:

• program code for receiving a pressure of the evaporated fuel processing system from a pressure sensor;
• program code for detecting a stop of the engine;
• program code for closing the vent-shut valve to close the evaporated fuel processing system after the stop of the engine is detected;
• program code for determining whether the evaporated fuel processing system has leakage after the evaporated fuel processing system is closed based on the detected pressure and a predetermined determination value;
• and
• program code for prohibiting the leakage determination if the detected pressure is not within a predetermined range.

An apparatus for determining leakage in an evaporated fuel processing system, the evaporated fuel processing system extending from a fuel tank through a canister to a purge passage through which evaporated fuel from the fuel tank is purged to an intake manifold of an engine, the canister comprising a vent-shut valve that communicates with the atmosphere, the apparatus comprising:

• a pressure sensor for detecting a pressure of the evaporated fuel processing system;
• means for detecting a stop of the engine;
• means for closing the vent-shut valve to close the evaporated fuel processing system after the stop of the engine is detected;
• means for determining whether the evaporated fuel processing system has leakage after the evaporated fuel processing system is closed based on the detected pressure and a predetermined determination value;
• and
• means for prohibiting the leakage determination if the detected pressure is not within a predetermined range.