Positive Crankcase Ventilation: Description and Operation

PCV Flow:

PURPOSE
The Positive Crankcase Ventilation ([1][2]PCV) system is used to provide more complete scanvenging of the crankcase vapors. Fresh air from the air cleaner is supplied to the crankcase, mixed with blow-by gasses,and then passed to the intake manifold.

PCV System:

OPERATION
The primary control is through the PCV valve is the which meters at a rate depending on manifold vacuum. 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 gases to back flow through the crankcase vent tube into the air inlet duct to be consumed by normal combustion.