Patent ID: 7366604

Claim:
A fuel vapor treatment system comprising: a canister configured to temporarily adsorb fuel vapor from a fuel tank; a fresh air introducing port fluidly connected to the canister to introduce fresh air into the canister with a fresh air introducing port on/off valve disposed in the fresh air introducing port to open and close the intake air introducing port of the canister; a purge line fluidly connected to the canister to send the fuel vapor adsorbed in the canister to an air intake system of an internal combustion engine by introducing fresh air into the canister through the fresh air introducing port and allowing the fresh air and fuel vapor to be drawn into the air intake system through a purge control valve disposed in the purge line; a pressure detecting device arranged and configured to detect a purge line pressure within the purge line; and a leak diagnosis control device configured and arranged to close the purge control valve and the fresh air introducing port on/off valve to close off the purge line after determining engine operation is stopped, and the leak diagnosis control device being further configured to conduct a leak determination to determine a leakage state of the purge line based on an amount by which the purge line pressure of the purge line decreases due to a temperature decrease occurring within a temperature region that is lower than a prior temperature that existed immediately after the engine was stopped.