Dodge RAM 1500 1998 Owner's Manual page 2580

DR
PCV VALVE (Continued)
Fig. 14 PCV VALVE/HOSE - 5.9L V-8
1 - PCV VALVE
2 - PCV VALVE HOSE CONNECTIONS
OPERATION
The PCV system operates by engine intake mani-
fold vacuum (Fig. 15). 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.
Fig. 15 TYPICAL CLOSED CRANKCASE
VENTILATION SYSTEM
1 - THROTTLE BODY
2 - AIR CLEANER
3 - AIR INTAKE
4 - PCV VALVE
5 - COMBUSTION CHAMBER
6 - BLOW-BY GASES
7 - CRANKCASE BREATHER/FILTER
EVAPORATIVE EMISSIONS
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.
When the engine is not operating or during an
engine pop-back, the spring forces the plunger back
against the seat (Fig. 16). This will prevent vapors
from flowing through the valve.
Fig. 16 ENGINE OFF OR ENGINE BACKFIRE - NO
VAPOR FLOW
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. 17). In this position there
is minimal vapor flow through the valve.
Fig. 17 HIGH INTAKE MANIFOLD VACUUM -
MINIMAL VAPOR FLOW
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. 18).
Fig. 18 MODERATE INTAKE MANIFOLD VACUUM -
MAXIMUM VAPOR FLOW
25 - 19