Evaporation Control System

Fig 2 EVAP Canister:

EVAPORATION CONTROL SYSTEM
The evaporation control system prevents the emission of fuel tank vapors into the atmosphere. When fuel evaporates in the fuel tank, the vapors pass through vent hoses or tubes to a charcoal canister. The canister temporarily holds the vapors. Through the duty cycle EVAP purge solenoid, the PCM allows intake manifold vacuum to draw vapors from the charcoal canister into the combustion chambers during certain operating conditions. The solenoid regulates vapor flow from the canister to the engine.

The evaporative system uses specially manufactured hoses. If they need replacement, only use original equipment fuel vapor resistant hose.

EVAP CANISTER
All vehicles use a sealed, maintenance free, evaporative (EVAP) canister. Fuel tank pressure vents into the canister. The canister temporarily holds the fuel vapors until intake manifold vacuum draws them into the combustion chamber. The powertrain control module (PCM) purges the canister through the duty cycle EVAP purge solenoid. The PCM purges the canister at predetermined intervals and engine conditions.

The canister mounts to a bracket behind the front fascia on the passengers side of the vehicle (Fig. 2). The vacuum and vapor tube connect to the top of the canister.

Fig. 3 Duty Cycle EVAP Purge Solenoid-Master Cylinder Removed:

DUTY CYCLE EVAP PURGE SOLENOID
The duty cycle EVAP purge solenoid regulates the rate of vapor flow from the EVAP canister to the throttle body. The Powertrain Control Module (PCM) operates the solenoid.

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.

When purging, the PCM energizes and de-energizes the solenoid approximately 5 or 10 times per second, depending upon operating conditions. The PCM varies the vapor flow rate by changing solenoid pulse width. Pulse width is the amount of time the solenoid energizes.

The solenoid attaches to a bracket on the driver's side strut tower (Fig. 3). To operate correctly, the solenoid must be installed with the electrical connector on top.