Patent ID: 6367458
Filing Date: 2002-04-09
Classification: F02M

Abstract:
A leak diagnostic device for an in-tank canister system connected to a suction system of an internal combustion engine, said in-tank canister system having a fuel tank, a vapor absorbing canister, a fuel vapor inlet passage fluidly connecting a fuel vapor inlet opening disposed in an upper interior space of the fuel tank to the canister via a negative pressure cut valve, an air inlet passage drawing air into the canister through an air inlet opening disposed outside the fuel tank, and a purge passage purging the fuel vapor along with air out of the canister into the suction system of the internal combustion engine via a purge control valve, said leak diagnostic device comprising:a negative pressure control valve being arranged to operatively connect and disconnect the suction system between the canister in a normal mode and the upper interior space of the fuel tank in a diagnosis mode; and a control unit having a pressure sensor arranged to measure pressure in the upper interior space of the fuel tank, said control unit being operatively coupled to said negative pressure control valve to shift said negative pressure control valve between said normal mode and said diagnosis mode, said control unit being configured to open the purge control valve with said negative pressure control valve in said normal mode to create a negative pressure in the fuel tank and to determine whether there is a leak based on the pressure measured by said pressure sensor.