초록 ▼

The present invention relates a method of detecting leaks and blockages in a fuel system. The leaks are detected using a RAMPOFF mode and a TANK mode. The RAMPOFF mode modifies the evaporative diagnostic purge logic to increase the ramp down rates of the evaporative purge duty cycle to aggressively

The present invention relates a method of detecting leaks and blockages in a fuel system. The leaks are detected using a RAMPOFF mode and a TANK mode. The RAMPOFF mode modifies the evaporative diagnostic purge logic to increase the ramp down rates of the evaporative purge duty cycle to aggressively shut off the purge solenoid valve for tests used to detect leaks as small as 0.02 inches in diameter. The TANK mode modifies the evaporative diagnostic purge logic to support aggressive purging requirements for tests used to detect larger leaks of greater than 0.04 inches in diameter. The MASS FLOW mode modifies the evaporative diagnostic purge logic to hold a constant purge mass flow rate necessary to detect blockages across a vent solenoid valve. The RAMPOFF mode, TANK mode, and MASS FLOW modes support evaporative diagnostics that are run continuously within a fuel system when acceptable engine operating conditions are present.

대표청구항 ▼

1. A method for detecting leaks and blockages in a fuel system, the method comprising the steps of:determining whether small leaks are present when a first set of operating conditions are present and when a tank hydrocarbon level does not exceed an allowable tank hydrocarbon threshold value using a

1. A method for detecting leaks and blockages in a fuel system, the method comprising the steps of:determining whether small leaks are present when a first set of operating conditions are present and when a tank hydrocarbon level does not exceed an allowable tank hydrocarbon threshold value using a RAMP OFF mode modified purge duty cycle; determining whether large leaks are present when a second set of operating conditions are present and when a tank hydrocarbon level does not exceed an allowable tank hydrocarbon threshold value using a RAMP OFF mode modified purge duty cycle; and determining whether the vent solenoid valve is blocked when a third set of operating conditions is present using a MASS FLOW mode modified purge duty cycle when said MASS FLOW mode modified purge duty cycle is called.