To accurately determine valve open failure of a back-flow valve provided in a purge passage supplying evaporated fuel to a suction pipe form a canister.
This device is provided with a valve for back flow prevention provided in the purge passage and a pressure sensor detecting pressure of evaporated fuel system including a fuel tank and the canister. The device is provided with a means detecting crossing of a reference level and pulsation wave form of operation cycle of a purge control valve based on output of the pressure sensor, a means defining phase of the crossing in relation to reference cycle, and a determination means determining an open valve failure of the valve for back flow prevention based on phase difference between the phase defined this time and phase defined predetermined number of cycles before. Pressure of the evaporated fuel system pulsates according to cyclic operation of the purge control valve. When valve open failure occurs on the back-flow valve, phase of pulsation is reversed. Valve open failure of the back-flow valve in the purge passage can be accurately determined by monitoring phase of pulsation of pressure of the evaporated fuel system.
TAKIZAWA OSAMU
KOSAKA YOSUKE
KON TAKASHI
