| 摘要 |
A method and apparatus for detecting leakage from an evaporative emission space (14, 18) of a vehicle fuel system by utilizing naturally occurring vacuum that can occur under certain favorable conditions after a fuel-consuming engine (12) that powers an automotive vehicle has been turned off. If there is no leakage, vapor pressure in the fuel system will begin to decrease. If it is assumed that the vapor pressure was approximately atmospheric when the engine was turned off, and that no leakage existed, ensuing cooling will create increasing vacuum in headspace of the fuel tank as the temperature drops. In the absence of leakage, a well-defined relationship exists. Measurements of physical parameters (24, 26) characterizing fluid conditions in the fuel tank are taken as cooling proceeds and processed. Results are evaluated to obtain leakage information.
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