SERVO CONTROLLED EVAP LEAK DETECTION SYSTEM

摘要

A method and system for testing an evaporative emission control system for leaks. The method begins by setting a variable reference orifice to a preselected diameter. Then, a vacuum pump evacuates a reference volume in the vicinity of the variable reference orifice. The reference volume is defined by the vacuum pump, and the reference orifice. Then, after a specified evacuation time, the method determines a pressure in the reference volume. That pressure is stored as the threshold test value. The method continues by evacuating the entire EVAP system for a predetermined time. A leak can then be identified if after the evacuation, the system pressure falls at least to the threshold test value. Switching the vacuum pump between the first and second positions is accomplished with a changeover valve having parallel airways configured for evacuating a small volume to the reference orifice and also evacuating the entire EVAP system.

主权项

1. A method for testing an evaporative emission control system for leaks, comprising
setting a variable reference orifice to a preselected diameter; evacuating a reference volume in the vicinity of the variable reference orifice, using a vacuum pump, the reference volume being defined by the vacuum pump, the reference orifice, and fluid communication lines associated with those devices; determining a pressure in the reference volume at the end of a specified evacuation time; storing the determined pressure as the threshold test value; evacuating the system for a predetermined time; and identifying the presence of a leak if, after the evacuation, the system pressure falls at least to the threshold test value.