Evaporation control system. Rollover valve

Evaporation control system

OPERATION

The evaporation control system prevents the emission of fuel tank vapors into the atmosphere. When fuel evaporates in the fuel tank, the vapors pass through vent hoses or tubes to a charcoal filled evaporative 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 engines use a duty cycle purge system. The PCM controls vapor flow by operating the duty cycle EVAP purge solenoid. Refer to Duty Cycle EVAP Canister Purge Solenoid.

When equipped with certain emissions packages, a Leak Detection Pump (LDP) will be used as part of the evaporative system for OBD II requirements.

Also refer to Leak Detection Pump.

NOTE: The evaporative system uses specially manufactured lines/hoses. If replacement becomes necessary, only use fuel resistant hose.

Rollover valve

DESCRIPTION

The fuel tank is equipped with two rollover valves.

The front valve is located on the top of the fuel pump module (Fig. 1). The other valve is located on the top rear of the fuel tank (Fig. 1).

Fig. 1 Rollover Valve Locations

1 - FUEL PUMP MODULE

2 - FRONT ROLLOVER VALVE

3 - FUEL FILTER/FUEL PRESSURE REGULATOR

4 - FUEL TANK

5 - EVAP LINE

6 - REAR ROLLOVER VALVE

OPERATION

The rollover valves will prevent fuel flow through the fuel tank vent (EVAP) hoses in the event of an accidental vehicle rollover. The EVAP canister draws fuel vapors from the fuel tank through these valves.

The rear valve cannot be serviced separately. If replacement is necessary, the fuel tank must be replaced. Refer to Fuel Tank Removal/Installation in Group 14, Fuel System. The front valve can be serviced separately.