Positive Crankcase Ventilation: Description and Operation

PCV Valve.:

Positive Crankcase Operation.:

Purpose:
The primary control is through the PCV valve which meters the flow at a rate depending on manifold vacuum.

Operation:
To maintain idle quality, the PCV valve restricts the flow when intake manifold vacuum is high. If abnormal operating conditions arise, the system is designed to allow excessive amounts of blow-by gasses to back flow through the crankcase vent tube into the air cleaner or clean air tube and to be consumed by normal combustion.

A positive crankcase ventilation (PCV) system is used to consume crankcase vapors in the combustion process instead of venting to atmosphere. Fresh air from the air cleaner assembly or clean air tube is supplied to the crankcase, mixed with blow-by gases and then passed through a positive crankcase ventilation (PCV) valve into the intake manifold.