Patent ID: 6804995
Filing Date: 2004-10-19
Classification: F02M

Abstract:
A fuel vapor treatment system comprising:a fuel tank; a canister fluidly coupled to the fuel tank and configured to adsorb fuel vapor evaporated from the fuel tank; a purge valve disposed to open and close piping that fluidly couples the canister to an intake passage of an internal combustion engine into which fuel vapor flows from the canister; a drain cut valve operatively coupled to the canister to open and close an atmospheric release port of the canister; an absolute pressure sensor configured and arranged to detect absolute pressure inside the fuel vapor treatment system and measure atmospheric pressure based on an open-closed statuses of the drain cut valve and the purge valve; and a failure diagnosis control device configured and arranged to close off a portion of the fuel vapor treatment system between the fuel tank and the purge valve and conduct a leak diagnosis when a permission condition is met, the leak diagnosis control device being configured to conduct the failure diagnosis based on atmospheric pressure and a pressure change inside the portion of the fuel vapor treatment system while the portion of the fuel vapor treatment system is closed off, the failure diagnosis control device being further configured to cancel a leak diagnosis result obtained by the leak diagnosis when a predetermined condition for canceling the leak diagnosis result is determined, the failure diagnosis control device being further configured to determine that the predetermined condition for canceling the leak diagnosis result is satisfied when a change in atmospheric pressure exceeds a prescribed value with the change in atmospheric pressure being detected by comparing a first output value detected by the absolute pressure sensor before conducting the leak diagnosis and a second output value detected by the absolute pressure sensor after conducting the leak diagnosis.