ENGINE OFF NATURAL VACUUM LEAKAGE CHECK FOR ONBOARD DIAGNOSTICS

摘要

A diagnostic method and system detects leaks in a vapor handling system of a vehicle that includes a fuel tank and a pressure/vacuum sensor that senses pressure and vacuum in the fuel tank. A canister recovers vapor from the fuel tank. A canister vent solenoid selectively provides atmospheric air to the canister. A controller connected to the canister vent solenoid and the pressure/vacuum sensor executes a leakage detection test that is capable of detecting leaks in the vapor handling system that have a diameter on the order of 0.020 inch. The leakage detection test includes a volatility test phase, a pressure phase, a vacuum phase, an analysis phase and a results phase. In other features, the leakage detection algorithm generates data sets having greater than 25 standard deviations between leakage and no-leakage data sets.