| 摘要 |
A system and method for detecting leakage from a evaporative emission space of an automotive vehicle fuel system. A reciprocating pump is operated in a pressurizing mode to build pressure in the space toward a nominal test pressure. The pressurizing mode involves operating the pump in a repeating cycle wherein the pump operates alternately in an accelerated pumping mode and a natural frequency pumping mode. During the pressurizing mode, a characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the space is measured. The number of times the cycle repeats is counted and compared to a predefined reference. When the cycle count exceeds the predefined reference, the test continues at a lower resolution for detecting leakage, and when the cycle count does not exceed the predefined reference and a measurement of the characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the space exceeds a predetermined reference pressure, the test continues at a higher resolution for detecting leakage. The invention is useful when overall test time is limited.
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