Evaporative Emissions: Notes

The EVAP system consists of the:

• EVAP canister purge valve.
• EVAP canister.
• EVAP canister vent solenoid.
• fuel vapor tube assembly (includes the FTP sensor).
• dual check valve (1.6L GTDI engine and 2.0L GTDI engine) (part of the canister purge valve).
• vapor ejector (1.6L GTDI engine and 2.0L GTDI engine) (part of the canister purge valve).
• Easy Fuel™ (capless) fuel tank filler pipe.

The EVAP system:

• utilizes an ORVR system that captures the fuel vapors from the vehicle's fuel tank during refueling.
• prevents hydrocarbon emissions from reaching the atmosphere.
• stores fuel vapors in the EVAP canister, that are generated during vehicle operation or hot soak, until they can be consumed by the engine during normal engine operation.
• routes the stored fuel vapors to the engine during engine operation.
• is controlled by the PCM which, using various sensor inputs, calculates the desired amount of purge flow. The PCM regulates the purge flow, induced by the application of intake manifold vacuum, by varying the duty cycle applied to the EVAP canister purge valve.

The fuel vapors are routed:

• from the fuel tank through the fuel vapor vent valve.
• to the EVAP canister through the fuel vapor tube assembly.
• to the engine when the EVAP canister purge valve is opened by the PCM.

The FTP sensor:

• is part of the fuel vapor tube assembly.
• monitors the pressure levels in the fuel tank.
• communicates the pressure reading to the PCM during the OBD II leak test.

The fuel vapor tube assembly:

• is located on the top of the fuel tank.
• is used to control the flow of fuel vapors entering the EVAP system.

The EVAP canister:

• is located under the rear of the vehicle.
• contains activated carbon.
• stores fuel vapors.

The Easy Fuel™ (capless) fuel tank filler pipe:

• relieves system vacuum below -3.5 kPa (-16.00 in H₂ O).

The EVAP canister vent solenoid:

• is normally open.
• seals the EVAP system for the inspection and maintenance (I/M 240) test and OBD II leak and pressure tests.
• is mounted to the EVAP canister.
• is repaired as a separate item.

The EVAP canister purge valve:

• is normally closed.
• regulates the purging of the EVAP canisters.
• is controlled by the PCM.
• is repaired as a separate item.
• is mounted to the intake manifold.

The dual check valve (1.6L GTDI engine and 2.0L GTDI engine):

• routes fuel vapors to the intake manifold when the intake manifold is not pressurized.
• routes fuel vapors to the vapor ejector when the intake manifold is pressurized.

The vapor ejector (1.6L GTDI engine and 2.0L GTDI engine):

• is a venturi.
• uses pressurized air from the turbocharger-to-CAC tube to route fuel vapors to the ACL outlet tube.

The EVAP system monitor:

• is a self-test strategy within the PCM which tests the integrity of the EVAP system.
• monitors the EVAP system for leaks.
• monitors electronic EVAP components for irrationally high or low voltages.
• monitors for correct EVAP system operation.
• uses negative and positive leak test methods to test and activate the EVAP system.

The engine ON EVAP leak-check monitor:

• is executed by the individual components of the enhanced EVAP system. Intake manifold vacuum is utilized to reach a target vacuum on the EVAP system. The FTP sensor is used by the engine ON EVAP leak-check monitor to determine if the target vacuum necessary to carry out the leak-check on the FTP system has been reached. Once target vacuum on the EVAP system is achieved, the change in EVAP system vacuum over a calibrated period of time determines if a leak exists.

The EONV EVAP leak-check monitor is executed:

• once the engine ON EVAP leak-check monitor is completed and the key is turned OFF. The EONV EVAP leak-check monitor determines if a leak is present when the naturally occurring change in the fuel tank pressure or vacuum does not exceed a calibrated limit during a calibrated amount of time. A separate, low-power consuming microprocessor in the PCM manages the EONV leak-check. The engine OFF EVAP leak-check monitor is executed by the individual components of the enhanced EVAP system.