Fuel system leak detection
Number of patents in Portfolio can not be more than 2000
United States of America Patent
Stats
-
Dec 26, 2000
Grant Date -
N/A
app pub date -
Jul 6, 1999
filing date -
Jul 6, 1999
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A vehicle fuel system has on-board diagnostics for leak testing with correction for different operating conditions. An electronic control unit (ECU) is arranged to carry out a periodic two stage leak test, when the engine is running. Stage A includes evacuation of the fuel tank, monitoring bleedup and recording the pressure rise dP.sub.-- A over a predetermined period A following increase of pressure to a predetermined value p2. Stage B includes measuring the amount dP.sub.-- B by which the pressure in the tank rises above atmospheric due to vapor generation over a predetermined period B following venting and closure fuel system. The ECU calculates a value X representative of leakage from the difference between dP.sub.-- A and dP.sub.-- B using a scaling factor K. The test duration is adjusted in accordance with measured values of fuel level and ambient temperature to ensure that the measured pressure changes are dependent on leakage over a range of operating conditions.
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