Positive Crankcase Ventilation: Description and Operation

Crankcase Ventilation Flow:

DESCRIPTION
A crankcase ventilation system is used to provide more complete scavenging of crankcase vapors.

OPERATION
Fresh air from the air cleaner through a filter is supplied to the crankcase, mixed with blow-by gases and then passed through a crankcase ventilation valve into the intake manifold. The primary control is through the crankcase ventilation valve, which meters the flow at a rate depending on manifold vacuum. To maintain idle quality, the crankcase ventilation 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 cleaner to be consumed by normal combustion.