Positive Crankcase Ventilation: Description and Operation

PCV Flow:

DESCRIPTION
The crankcase ventilation system is used to provide more complete scavenging of the crankcase vapors. Fresh air from the air cleaner is supplied to the crankcase, mixed with blow-by gases and then passed through a crankcase ventilation valve (1) into the intake manifold.

The primary control is through the crankcase ventilation valve which meters the flow at a rate depending on manifold vacuum.

PCV Valve:

OPERATION
To Maintain idle quality, the valve (1) restricts the flow when intake manifold vacuum is high. Whenever abnormal operating condition arise, the system allows excessive amounts of blow-by gases to back flow through the crankcase vent tube into the rear air duct to be consumed by normal combustion