Canister Purge Solenoid: Description and Operation

Fig 21 Proportional Purge Solenoid:

PURPOSE
The proportional purge solenoid regulates the rate of vapor flow from the EVAP canister to the throttle body. The PCM operates the solenoid.

OPERATION
During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged.

The proportional purge solenoid operates at a frequency of 200 hz and is controlled by an engine controller circuit that senses the current being applied to the proportional solenoid and then adjusts the current to achieve the desired purge flow. The proportional purge solenoid controls the purge rate of fuel vapors from the vapor canister and fuel tank to the engine intake manifold.

The purge system starts after closed llop operation begins and after it reaches a specified temperature and the programmed time delay ends. During normal operatioin, the PCM energizes and de-energizes the solenoid.
The PCM varies the vapor flow rate by changing the solenoid pulse width. Pulse width is the amount of time the solenoid is energized.

The solenoid attaches to a bracket near the front engine mount (Fig. 21). To operate correctly, the solenoid must be installed with the electrical connector on top.