C 2500 Truck 2WD V8-305 5.0L VIN M SFI (1997)
Positive Crankcase Ventilation: Description and Operation
Crankcase Ventilation Valve Cross Section
EVAP System
DESCRIPTION
A crankcase ventilation system is used in order to provide a more complete scavenging of crankcase vapors. The air cleaner supplies fresh air
through a filter to the crankcase. The crankcase mixes the fresh air with blow-by gases. This mixture then passes through a crankcase ventilation
valve into the intake manifold.
The primary control is through the crankcase ventilation valve (1), which meters the flow at a rate depending on the manifold vacuum. In order to
maintain an idle quality, the crankcase ventilation valve restricts the flow when the intake manifold vacuum is high. If abnormal operating
conditions arise, the system is designed to allow the excessive amounts of blow-by gases to back flow through the crankcase vent tube into the air
cleaner in order to be consumed by normal combustion.
OPERATION
