W 250 Pickup V8-5.9L VIN Z (1991)
Positive Crankcase Ventilation: Description and Operation
Positive Crankcase Ventilation (PCV) System
Positive Crankcase Ventilation (PCV) System
SYSTEM OPERATION
The purpose of the PCV system is to reduce hydrocarbon (HC) and carbon monoxide (CO) emissions created by engine blow-by. This system is a
closed crankcase ventilation system that consists of a PCV valve, a hose extending from the PCV valve to the throttle body, a crankcase inlet air filter,
and a hose connecting the filter to the air cleaner assembly.
The PCV system operates on manifold vacuum: Fresh air is drawn in through the air cleaner and crankcase inlet filter, into the engine, and the vapors
that come out through the PCV valve are blow-by gases. These gases are drawn through the PCV hose and into the throttle body, they mix with the
calibrated air/fuel mixture, and get burned and expelled with the exhaust gases.
