Fuel vapor purging control system for automotive vehicle

A fuel vapor purging control system for an automotive vehicle comprising:

• a canister adapted for capturing therein fuel vapor generated from a fuel tank, said canister being arranged in a purge passage communicating between the fuel tank and an induction system of an engine;
• a purge control valve operable to control a purge rate of the fuel vapor purged from said canister, said purge control valve being arranged in a portion of the purge passage between said canister and the induction system of the engine;
• a purge air induction passage communicating between said canister and an air inlet port which is exposed to atmospheric pressure;
• air source means for supplying pressurized air to said canister through said purge air induction passage;
• pressure detecting means for detecting negative pressure relative to the atmospheric pressure in the induction system of the engine to provide a signal indicative thereof;
• and
• purge air control means for selectively establishing first and second purge air supply modes, the first purge air supply mode being to allow air under the atmospheric pressure to be introduced into said canister through the air inlet port, the second purge air supply mode being to supply the pressurized air from said air source means to said canister, said purge air control means being responsive to the signal from said pressure detecting means to establish the second purge air supply mode when the negative pressure is smaller than a preselected threshold value.