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OPERATION The PCV system operates by engine intake mani- fold vacuum. Filtered air is routed into the crankcase The PCV valve contains a spring loaded plunger. This plunger meters the amount of crankcase vapors 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 against the seat (Fig. 11). This will prevent vapors During periods of high manifold vacuum, such as idle or cruising speeds, vacuum is sufficient to com- During periods of moderate manifold vacuum, the plunger is only pulled part way back from inlet. This Fig. 9 PCV Valve/Oil Filler Tube (Housing)—4.7L Engine 1 – O-RING Fig. 10 PCV System Hoses/Tubes—4.7L Engine 1 – FRESH AIR FITTING Fig. 11 Engine Off or Engine Pop-Back—No Vapor Flow 25 - 28 EMISSION CONTROL SYSTEMS DN DESCRIPTION AND OPERATION (Continued) |