FAILURE DETECTING DEVICE FOR EVAPORATED FUEL TREATMENT DEVICE

PROBLEM TO BE SOLVED: To provide a failure detecting device for an evaporated fuel treatment device that is also applicable to a plug-in hybrid vehicle and easily detects abnormal points.SOLUTION: A control valve 7 is provided at the intermediate part of a first passage 5 making a fuel tank 2 and a canister 6a communicate with each other. Pressure sensors 14, 15 are provided so as to detect tank internal-pressure and canister internal-pressure, respectively. When the tank internal-pressure is higher than leakage diagnosable pressure Pd, the control valve is closed after opening it for a prescribed period of time in order to diagnose the presence or absence of leakage by change in respective internal pressure thereafter. Leakage diagnosis is executed by using high pressure in the fuel tank, thereby eliminating the need for additionally providing a high-pressure generating device. When applied to a plug-in hybrid vehicle and even if evaporated fuel in the fuel tank is increased due to the long-term no-use of fuel, the evaporated fuel in the fuel tank can be adsorbed in the canister in the cycle of leakage diagnosis, thereby inhibiting the tank internal pressure of the fuel tank from becoming high.