The evaporation control system prevents the emission of fuel tank vapors into the atmosphere. When fuel in the tank evaporates, the vapors pass through vent hoses or tubes to a charcoal canister. The canister temporarily holds the vapors. The Powertrain Control Module (PCM) allows intake manifold vacuum to draw vapors into the combustion chambers during certain operating conditions.
All of these engines use a duty cycle purge system. The PCM controls the vapor flow by operating the the duty cycle EVAP purge solenoid.
All vehicles have 2 rollover valves on top of the fuel tank. The valves prevent the fuel flow through the tank vent hoses in case the vehicle should roll over.Evaporative Canister
All vehicles use a sealed, maintenance free evaporative canister. Fuel tank pressure vents into the canister. The canister temporarily holds the fuel vapors until the intake manifold vacuum draws them into the combustion chamber. The PCM operates the canister through the EVAP purge solenoid. The PCM then purges the canister at the predetermined intervals and engine conditions.
The canister mounts to the bracket below the air cleaner. The canister protrudes through the top of the bracket. The vacuum and vapor tube connect to the top of the canister.Duty Cycle Evaporation (EVAP) Purge Solenoid
The PCM controls vapor flow by operating the 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.
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 PCM de-energizes the solenoid during open loop operation.
The engine enters closed loop operation after it reaches a specified temperature and the time delay ends. During closed loop operation, the engine computer energizes and de-energizes the solenoid approximately 5-10 times per second, depending upon operating conditions. The engine computer varies the vapor flow rate by changing solenoid pulse width. Pulse width is the amount of time the solenoid energizes. The engine computer adjusts solenoid pulse width based on engine air flow.
A rubber boot covers the duty cycle EVAP purge solenoid. The solenoid attaches to a bracket mounted to the right engine mount. The top of the solenoid has the word TOP on it. The solenoid will not operate unless it is installed correctly.
REMOVAL & INSTALLATION
All vehicles are equipped with a Vehicle Emission Control Information (VECI) label which is located in the engine compartment. The label contains emission specifications and vacuum hose routings. All hoses must be connected and routed as shown on the label.Rollover Valve
- Raise and support the vehicle.
- Remove the fuel pump module.
- Wedge the blade of a straight flat bladed tool between the rubber grommet and the fuel pump module. Do not pry between the valve and the grommet.
- Use a second tool as a support to pry the valve and grommet assembly from the module.
- To remove the grommet, place the valve upright on a flat surface. Push down on the grommet and peel it off the valve.
- Install the rubber grommet in the fuel pump module.
- Lubricate the grommet with a light coating of power steering fluid, then push the valve downwards into the grommet. Twist the valve until the ports are properly positioned.
- Install the fuel pump module.
EVAP Purge Solenoid Valve
See Figures 1 and 2
The EVAP purge solenoid valve is located on a bracket attached to the air cleaner.
- Slide the valve off of the bracket.
- Disconnect the electrical wire to the valve.
- Disconnect the vacuum hoses from the valve.
- Remove the valve.
- Attach the vacuum hoses to the valve.
- Connect the electrical wiring.
- Slide the valve onto the bracket attached to the air cleaner.
See Figures 3, 4 and 5
It is necessary to raise and support the vehicle to remove and install the canister.
- Slide the EGR purge solenoid off the bracket on the air cleaner.
- Remove the screw from the air cleaner.
- Remove the air inlet duct from the air cleaner.
- Pull the air cleaner straight up and remove it.
- Raise and support the vehicle.
- Detach the hoses from the top of the EVAP canister.
- Remove the 3 nuts from the EVAP canister.
- Install the canister from under the vehicle.
- Install the 3 nuts and tighten the canister.
- Attach the hose to the canister.
- Lower the vehicle.
- Install the air cleaner and tighten down.
- Attach the air inlet duct to the air cleaner.
- Slide the EGR purge solenoid onto the bracket.