Positive Crankcase Ventilation Valve: Description and Operation

PCV Internal Drawing:

PURPOSE
The Positive Crankcase Ventilation (PCV) system uses intake manifold vacuum to ventilate blow-by fumes from the crankcase and return the fumes to the intake manifold for combustion.

OPERATION
The PCV valve varies the amount of blow-by gases returned to the intake manifold based on available engine vacuum. The PCV valve also prevents the entry of combustion backfiring into the crankcase.