Patent ID: 6196203
Filing Date: 2001-03-06
Classification: F02M

Abstract:
A method of controlling a canister vent valve used in an evaporative emissions control system to reduce running losses during purging of fuel vapors from a charcoal canister to an air intake of an internal combustion engine, wherein the control system includes a purge valve connected between the canister and air intake, with the canister being connected to receive evaporated fuel from a fuel tank that is used to supply fuel to the engine, the method comprising the steps of:monitoring gas pressure within the fuel tank,closing the canister vent valve while the engine is operating and the purge valve is open when the pressure within the fuel tank exceeds a threshold, andopening the canister vent valve while the engine is operating and the purge valve is open when the pressure within the tank falls below a lower limit, whereby the canister vent valve can be held closed during purging until the pressure within the fuel tank drops to below the lower limit.