Positive Crankcase Ventilation: Description and Operation

PCV System:

PURPOSE
This system returns blow-by gas to both the intake manifold and air inlet tubes.
OPERATION
The positive crankcase ventilation (P.C.V.) valve is provided to conduct crankcase blow-by gas to the intake manifold.
During partial throttle operation of the engine, the intake manifold sucks the blow-by gas through the P.C.V. valve. Normally, the capacity of the valve is sufficient to handle any blow-by and a small amount of ventilating air. The ventilating air is then drawn from the air inlet tubes, through the hose connecting air inlet tubes to rocker cover, into the crankcase. Under full-throttle condition, the manifold vacuum is insufficient to draw the blow-by flow through the valve, and its flow goes through the hose connection in the reverse direction. On vehicles with an excessively high blow-by some of the flow will go through the hose connection to the air inlet tubes under all conditions.