Method of controlling a vapor storage canister for a purge control system

A method of controlling a vapor storage canister for a purge control system of an internal combustion engine, said method comprising the steps of:

• determining whether predetermined conditions are right for controlling a potentially loaded vapor storage canister;
• maintaining normal fuel feedback operation if predetermined conditions are not right for controlling the vapor storage canister;
• determining if the vapor storage canister is loaded by activating the purge solenoid if predetermined conditions are right for controlling the vapor storage canister;
• comparing whether an instantaneous oxygen (O2) controller signal minus an average O2 controller signal before the purge solenoid is turned on is greater than a predetermined fuel shift value;
• maintaining normal fuel feedback operation if the instantaneous O2 controller signal minus the average O2 controller signal is not greater than the fuel shift value indicating the vapor storage canister is not loaded;
• ramping the purge solenoid duty cycle up to maximize purge if the vapor storage canister is loaded;
• incrementing or decrementing a total purge multiplier;
• and
• using said total purge multiplier to vary the amount of fuel being delivered to the engine.