Evaporative Emissions

EVAPORATIVE EMISSIONS

Part 1:

Part 2:

The evaporative emissions (EVAP) system:
- prevents hydrocarbon emissions from reaching the atmosphere.
- stores fuel vapors in the evaporative emissions (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 powertrain control module (PCM), which uses various sensor inputs to calculate the desired amount of purge how. 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.
- has an evaporative emissions (EVAP) test port for test purposes.

The fuel vapors are routed:
- from the fuel tank through the fuel vapor vent valves.
- to the (EVAP) canister through a vapor line.
- to the engine when the EVAP canister purge valve is opened by the PCM.

The fuel tank pressure (FTP) sensor:
- monitors the pressure levels in the fuel tank.
- communicates the pressure reading to the PCM during the OBD II leak test.

The evaporative emissions (EVAP) canister:
- is located above the spare tire carrier behind the fuel tank.
- contains activated carbon.
- stores fuel vapors.

The fuel tank filler cap:
- relieves system pressure above 14 kPa (56.21 inches H2O).
- relieves system vacuum below 3.8 kPa (15.26 inches H2O).

The canister vent solenoid:
- is normally open.
- seals the evaporative emissions system for the OBD II leak and pressure tests.
- is mounted to the evaporative emissions canister.
- is repaired as a separate item.

The evaporative emissions (EVAP) canister purge valve:
- is normally closed.
- regulates the purging of the EVAP canister.
- is controlled by the PCM.

The evaporative emissions (EVAP) system test port:
- is located in the EVAP canister purge valve.
- is used to connect the Evaporative Emissions System Leak Tester to the EVAP system.