To precisely discriminate and diagnose abnormalities of a purge control valve.
This purge control valve 44 opened and closed according to a control signal from an ECU is arranged on the way of a purge passage 43 (43a, 43b) connecting a canitor 36 to an intake passage 12. The ECU determines presence of abnormality of the purge control valve 44 based on inner pressure of the canitor 36, upon receiving starting of purge cut, immediately after starting an engine 11. When abnormality occurrence is determined in the purge control valve 44, it is determined whether or not the purge control valve 44 is in reversed assembling state based on the inner pressure of the canistor 36 under the state that the purge control valve 44 is closed and intake pressure is a specified value or lower. After forcible closing, it is determined whether the purge control valve 44 is in an open sticking state or a foreign material biting state based on the inner pressure of the canistor 36.
KAWASE KENICHIRO
TAGA TAKANORI
SHIMAZAKI NORIKAZU
AISAN IND