Initialization method for an automotive evaporative emission leak detection system

An evaporative emission control for an engine-powered automotive vehicle having a fuel storage system, the fuel storage system including an evaporative emission space containing volatile fuel vapors generated by the volatilization of fuel in the storage system, a system detecting volatile fuel vapor leakage from the evaporative emission space;

• and a purge valve coupling the evaporative emission space to the engine, the purge valve regulating a flow of the volatile fuel vapors to be combusted in the engine during conditions conducive to purging, the evaporative emission control comprising:
• a selectively operable prime mover pumping gaseous fluid with respect to the evaporative emission space;
• a selectively operable valve operating in first and second conditions, the first condition allowing the prime mover to move gaseous fluid with respect to the evaporative emission space, and the second condition disallowing the prime mover to move gaseous fluid with respect to the evaporative emission space;
• and
• a sensor providing an electric signal related to pressure in the evaporative emission space, the electric signal controlling operation of the prime mover and of the valve;
• wherein the leak detection system initializes the evaporative emission space preparatory to performing a leak detection test, the initializing including causing the pump to create a differential between pressure in the evaporative emission space and atmospheric pressure sufficient to perform a leak detection test, and the initializing including alternately increasing the created pressure differential above a nominal pressure differential and decreasing the created pressure differential below the nominal pressure differential, a plurality of cycles over time, within a range of differential pressures sufficient to perform a leak detection test.

A method of performing a leak detection test on an evaporative emission space of a fuel storage system of an engine-powered automotive vehicle evaporative emission control, the fuel storage system including an evaporative emission space containing volatile fuel vapors generated by the volatilization of fuel in the storage system, a system detecting volatile fuel vapor leakage from the evaporative emission space, and a purge valve coupling the evaporative emission space to the engine, the purge valve regulating a flow of the volatile fuel vapors to be combusted in the engine during conditions conductive to purging, the method comprising:

• initializing the evaporative emission space, the initializing including:
• creating a differential between pressure in the evaporative emission space and atmospheric pressure, and
• alternately increasing the created pressure differential above a nominal pressure differential and decreasing the creating pressure differential below the nominal pressure differential, a plurality of cycles over time, within a range of differential pressures sufficient to operate the system detecting volatile fuel vapor leakage;
• and
• isolating the evaporative emission space from communication with both the engine and atmosphere.