Evaporative Emissions System: Description and Operation

Midship Fuel Tank:

Aft-Of-Axle Fuel Tank:

The fuel tank pressure sensor:
- monitors the fuel tank pressure.
- displays the pressure reading during the OBD II purge monitor.

The fuel tank filler cap:
- relieves system pressures above 14 kPa (2 psi).
- relieves system vacuum below 3.8 kPa (0.5 psi).

The evaporative emission canister purge valve (EVAP canister purge valve):
- regulates the purging of the evaporative emissions canister (EVAP canister).
- controlled by the Powertrain Control Module (PCM).

The evaporative emissions canister:
- contains activated carbon.
- stores fuel vapors.

The evaporative emissions canisters are located:
- on the left hand side main frame member at the rear for the regular van and wagon with the mid ship fuel tank.
- on the rear frame crossmember for the extended van and wagon with mid ship fuel tank.
- on the left hand side mainframe member near the middle for the 37-gallon aft-of-axle fuel tank.
- on the left hand side mainframe member near the middle for the 55-gallon aft-of-axle fuel tank.

Two canisters in series are required.

The canister vent solenoid:
- seals the evaporative emissions system during the OBD II leak check.
- is mounted on the evaporative emissions canister.
- is repairable as a separate item.

During a refueling event the fuel vapors are routed from the fuel tank through the fuel tank filler pipe. When the fuel tank is at its rated capacity, the fuel level rises to close off the fuel tank filler pipe.

The pressure in the fuel tank will rise and cause fuel dispensing nozzle to shut off.

The evaporative emissions system:
- prevents hydrocarbon emissions from reaching the atmosphere.
- stores fuel vapors in the evaporative emissions canister.
- returns the stored fuel vapors to the engine during engine operation.

The fuel vapors are routed:
- from the fuel tank through the evaporative emission valve.
- through the evaporative emissions fuel vapor control valve.
- to the evaporative emissions carbon canister.
- from the evaporative emissions canister to the evaporative emission canister purge valve to the engine.
- the evaporative emission canister purge valve is controlled by the powertrain control module (PCM).