Evaporative Emissions System: Description and Operation

Component Location:

The evaporative emission system:
^ Prevents hydrocarbon emissions from reaching the atmosphere.
^ Stores fuel vapor in the Evaporative Emission Canisters (EVAP canister).
^ Returns the stored fuel vapors to the engine during engine operation.
^ Has an evaporative emission test port for test purposes.
^ Has a fresh air vent hose normally routed into a clean and dry location.

The fuel vapors are routed:
^ From the fuel tank through the fuel vapor control valve tube assembly.
^ Vapors are then routed through the EVAP canister purge outlet tube to the engine when the Evaporative Emission Canister Purge Valve (EVAP canister purge valve) is opened by the Powertrain Control Module (PCM).

The fuel tank pressure sensor:
^ Monitors the pressure in the fuel tank.
^ Provides a fuel tank pressure reading to the powertrain control module during the OBDII Test.
^ Is located inline above the fuel tank, and serviced as a fuel vapor control valve tube assembly.

The evaporative emissions canisters:
^ Are located near the rear of the vehicle.
^ Contain activated carbon.
^ Store fuel vapors.

The fuel tank filler cap:
^ Relieves system pressure above 14 kPa (2 psi).
^ Relieves system vacuum at 3.8 kPa (0.55 psi).

The canister vent solenoid:
^ Seals the evaporative emissions system for the OBDII leak check.
^ Is mounted in the evaporative emissions canister bracket, inline with the evaporative emissions canisters.
^ Is serviced as a separate item.

The evaporative emission canister purge valve:
^ Regulates purging of the evaporative emissions canister.
^ Is controlled by the powertrain control module.

Fuel vapor control valve tube assembly:
^ Consists of the fuel tank mounted fuel vapor control valve, inline fuel tank pressure sensor and the fuel vapor vent valve.
^ Prevents suspended liquid fuel from being drawn into the evaporative emission canister along with the fuel vapors.
^ Returns the liquid to the tank.