Apparatus for detecting leakage in an evaporated fuel processing system

摘要

An apparatus for determining leakage in an evaporated fuel processing system is provided. The evaporated fuel processing system extends 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 comprises a vent-shut valve that communicates with the atmosphere. The apparatus comprises a pressure sensor for detecting a pressure of the evaporated fuel processing system and a control unit connected to the pressure sensor. The control unit detects a stop of the engine. After the stop of the engine is detected, the control unit closes the vent-shut valve to close the evaporated fuel processing system. The control unit determines 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. The control unit prohibits the leakage determination if the detected pressure is not within a predetermined range. Thus, it is prevented that a state occurs where the vent-shut valve does not open due to the pressure of the evaporated fuel processing system when the leakage determination is being performed.