Patent ID: 7405917

Claim:
A method of determining a functional status of an electro-mechanical valve having a solenoid and plunger comprising the steps of: determining an electro-mechanical switching time, (t ems ), of a valve based on an electrical characteristic responsive to the solenoid; determining the (t ems ) includes determining a beginning and an end of a time window, and wherein determining the beginning of the time window includes the steps of: evaluating the current supplied to the solenoid over time; evaluating a valve switching pilot voltage (V c ) over time; determining when a slope of the (V c ) reaches a predetermined negative value and assigning that time as a switch on time; and adding a predetermined time value to the switch on time to determine the beginning of the time window; comparing the (t ems ) to a tolerance value; and generating a valve status signal dependant on a result of the comparison.