| 主权项 |
1. A diagnostic method for an evaporative emission control system for a vehicle having an engine comprising a fuel tank pressure sensor, a purge flow control valve, and a vacuum bypass valve, said method comprising:
(a) closing the purge flow control valve, opening the vacuum bypass valve, and initiating a timer; (b) determining whether the pressure sensed by the fuel tank pressure sensor is stabilized; (c) if the pressure sensed by the fuel tank pressure sensor is stabilized: (d) closing the vacuum bypass valve and recording an initial reading from the fuel tank pressure sensor, (e) opening the purge flow control valve a predetermined amount, (f) determining whether the timer has expired; (g) if the timer has not expired, determining whether the pressure sensed by the fuel tank pressure sensor is greater than or equal to the initial reading from the fuel tank pressure sensor, and (h) if the pressure sensed by the fuel tank pressure sensor is greater than or equal to the initial reading from the fuel tank pressure sensor, closing the purge flow control valve and completing the test method successfully; (i) initiating a vacuum stabilization timer contemporaneously with the timer; and if at said step (b) of determining whether the pressure sensed by the fuel tank pressure sensor is stabilized, the pressure sensed by the fuel tank pressure sensor is not stabilized; (j) determining whether the vacuum stabilization timer has expired, and
if the vacuum stabilization timer has not expired, repeating said method starting at said step of (b) determining whether the pressure sensed by the fuel tank pressure sensor is stabilized. |
