If there is no leak the pump will quit. If there is a
leak, the test is terminated at the end of the test
mode.
If there is no leak, the purge monitor is run. If the
cycle rate increases due to the flow through the
purge system, the test is passed and the diagnostic is
complete.
The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.
A typical system schematic is shown in (Fig. 3).
POSITIVE CRANKCASE VENTILATION (PCV)
SYSTEM
DESCRIPTION
All 3.9L V-6 and 5.2/5.9L V-8 are equipped with a
closed crankcase ventilation system and a positive
crankcase ventilation (PCV) valve.
This system consists of a PCV valve mounted on
the cylinder head (valve) cover with a hose extending
from the valve to the intake manifold. Another hose
connects the opposite cylinder head (valve) cover to
the air cleaner housing to provide a source of clean
air for the system. A separate crankcase breather/fil-
ter is not used.
OPERATION
The PCV system operates by engine intake mani-
fold vacuum (Fig. 5). Filtered air is routed into the
crankcase through the air cleaner hose. The metered
air, along with crankcase vapors, are drawn through
the PCV valve and into a passage in the intake man-
ifold. The PCV system manages crankcase pressure
and meters blow by gases to the intake system,
reducing engine sludge formation.
The PCV valve contains a spring loaded plunger.
This plunger meters the amount of crankcase vapors
Fig. 3 Evaporative System Monitor Schematic—Typical
1 – DUTY CYCLE PURGE SOLENOID (DCPS) DRIVER
2 – POWERTRAIN CONTROL MODULE (PCM)
3 – 3-PORT SOLENOID DRIVER
4 – REMOTE FILTER
5 – COMBINED CANISTER VENT VALVE & LEAK DETECTION
PUMP
6 – CANISTER
7 – TANK ROLLOVER VALVE & VAPOR FLOW CONTROL
ORIFICE
8 – INTAKE MANIFOLD
9 – THROTTLE BODY
10 – DCPS
11 – SWITCH SIGNAL INPUT TO THE PCM
12 – ENGINE VACUUM LINE
25 - 26 EMISSION CONTROL SYSTEMS DN
DESCRIPTION AND OPERATION (Continued)
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