Patent ID: 6182642
Filing Date: 2001-02-06
Classification: F02M

Abstract:
An apparatus for detecting a leak in an evaporative emission control system including a fuel vapor flow passage which extends from a fuel tank to a purge control valve by way of a canister, the apparatus comprising:a device for defining an atmospheric vent in communication with the open air;a motor driven air pump having an outlet;a directional control valve for connecting said fresh air vent selectively to one of said atmospheric vent and said outlet of said air pump;a bypass conduit providing communication between a fresh air inlet of said canister and said outlet of said air pump while bypassing said directional control valve, said bypass conduit having a reference orifice;means for detecting a first current through said air pump when said air pump is CN and said directional control valve is in a position of connecting said fresh air inlet to said atmospheric vent;means for detecting a second current through said air pump after lapse of a predetermined time from establishment of a condition in which said air pump is ON and said directional control valve is in a position of connecting said fresh air inlet to said outlet of said air pump;means for comparing said second current with said first current and judging if a leak is present in said fuel vapor flow passage;means for detecting a temperature of fuel in said fuel tank; andmeans for determining said predetermined time variably on the basis of said temperature of fuel.