Dodge 2000 DURANGO Service Manual page 1032

25 - 28 EMISSION CONTROL SYSTEMS
DESCRIPTION AND OPERATION (Continued)
Fig. 9 PCV Valve/Oil Filler Tube (Housing)—4.7L
1 – O-RING
2 – LOCATING TABS
3 – CAM LOCK
4 – OIL FILLER TUBE
5 – PCV LINE/HOSE
6 – PCV VALVE
OPERATION
The PCV system operates by engine intake mani-
fold vacuum. Filtered air is routed into the crankcase
through the air cleaner hose and crankcase breath-
ers. The metered air, along with crankcase vapors,
are drawn through the PCV valve and into a passage
in the intake manifold. 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
routed into the combustion chamber based on intake
manifold vacuum.
TYPICAL PCV valves are shown in (Fig. 11), (Fig.
12) and (Fig. 13).
When the engine is not operating, or during an
engine pop-back, the spring forces the plunger back
Engine
Fig. 10 PCV System Hoses/Tubes—4.7L Engine
1 – FRESH AIR FITTING
2 – CONNECTING TUBES/HOSES
3 – CRANKCASE BREATHERS (2)
4 – RUBBER HOSE
5 – AIR CLEANER RESONATOR
against the seat (Fig. 11). This will prevent vapors
from flowing through the valve.
Fig. 11 Engine Off or Engine Pop-Back—No Vapor
During periods of high manifold vacuum, such as
idle or cruising speeds, vacuum is sufficient to com-
pletely compress spring. It will then pull the plunger
to the top of the valve (Fig. 12). In this position there
is minimal vapor flow through the valve.
During periods of moderate manifold vacuum, the
plunger is only pulled part way back from inlet. This
results in maximum vapor flow through the valve
(Fig. 13).
Flow
DN