EVAPORATIVE EMISSION CONTROLS
TABLE OF CONTENTS
page page
DESCRIPTION AND OPERATION
EVAPORATION CONTROL SYSTEM ..........24
ROLLOVER VALVE .......................24
EVAPORATION (EVAP) CANISTER ...........25
DUTY CYCLE EVAP CANISTER PURGE
SOLENOID ............................25
LEAK DETECTION PUMP (LDP)..............25
POSITIVE CRANKCASE VENTILATION (PCV)
SYSTEM ..............................26
POSITIVE CRANKCASE VENTILATION (PCV)
SYSTEM—4.7L ENGINE ..................27
VEHICLE EMISSION CONTROL
INFORMATION (VECI) LABEL ..............29
DIAGNOSIS AND TESTING
PCV VALVE TEST—3.9/5.2/5.9L ENGINE .......29
PCV VALVE/PCV SYSTEM TEST—4.7L V-8
ENGINE ..............................30
VACUUM SCHEMATICS ....................31
LEAK DETECTION PUMP (LDP)..............31
REMOVAL AND INSTALLATION
PCV VALVE—4.7L V-8 ENGINE ..............31
EVAPORATION (EVAP) CANISTER ...........32
DUTY CYCLE EVAP CANISTER PURGE
SOLENOID ............................32
ROLLOVER VALVE(S) .....................33
LEAK DETECTION PUMP (LDP)..............33
SPECIFICATIONS
TORQUE CHART .........................34
DESCRIPTION AND OPERATION
EVAPORATION CONTROL SYSTEM
OPERATION
The evaporation control system prevents the emis-
sion 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 evap-
orative canister. The canister temporarily holds the
vapors. The Powertrain Control Module (PCM) allows
intake manifold vacuum to draw vapors into the com-
bustion chambers during certain operating condi-
tions.
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 man-
ufactured lines/hoses. If replacement becomes nec-
essary, 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).
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
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
25 - 24 EMISSION CONTROL SYSTEMS DN
To Next Page
Loading...
