Patent ID: 6837224

Claim:
An evaporated fuel treatment device for internal combustion engine that uses a canister to absorb evaporated fuel generated in a fuel tank for evaporated fuel treatment purposes, said device comprising: a sealing valve for controlling the continuity between said fuel tank and said canister; a purge control valve for controlling the continuity of a purge path for communication between said canister and the internal combustion engine; a differential pressure generation means for producing a pressure differential between the inside and the outside of the canister; a leak check means for activating said differential pressure generation means while said purge control valve is closed, and conducting a system leak check in accordance with a resulting pressure generated within a hermetically closed space containing said canister or within a hermetically closed space containing said fuel tank; and a sealing valve diagnostic means for conducting a failure diagnostic check on said sealing valve simultaneously with the execution of processing for said leak check; wherein said sealing valve diagnostic means comprises an open failure diagnostic means for activating said differential pressure generation means while said purge control valve and said sealing valve are closed, and conducting an open failure diagnostic check on said sealing valve in accordance with a resulting pressure generated within a hermetically closed space containing said canister or within a hermetically closed space containing said fuel tank; and a close failure diagnostic means for conducting a close failure diagnostic check on said sealing valve in accordance with a differential pressure that is generated between both sides of said sealing valve upon said open failure diagnostic check.