Fault diagnostic apparatus of evaporation purge system

摘要

To obtain a fault diagnostic apparatus of an evaporation purge system by which a fault detection of a purge vent valve can accurately be performed with no wrong judgment. There are included: a tank internal pressure detecting means for detecting an internal pressure of a fuel tank; a valve control means for controlling closing and opening of a purge control valve and the purge vent valve; a purge control valve fault detecting means for detecting a fault of the purge control valve on the basis of a detected output of the tank internal pressure detecting means when the purge control valve and the purge vent valve are closed; and a purge vent valve fault detecting means for detecting a fault of the purge vent valve on the basis of the detected output of the tank internal pressure detecting means when the purge control valve and the purge vent valve are open, and the purge vent valve fault detecting means performs the fault detection of the purge vent valve only when the purge control valve fault detecting means judges that the purge control valve is normal.