Positive Crankcase Ventilation: Description and Operation

CAUTION: Do not remove any part of the engine emission control system. Operating the engine without the engine emission control system intact will reduce fuel economy and engine ventilation. This will weaken engine performance and shorten engine life.

The Positive Crankcase Ventilation (PCV) system:
^ uses intake manifold vacuum to ventilate blow-by fumes from the crankcase.
^ returns the fumes to the intake manifold for combustion.

The Positive Crankcase Ventilation (PCV) valve:
^ varies the amount of blow-by gases returned to the intake manifold based on available engine vacuum.
^ prevents the entry of combustion backfiring into the crankcase.

The PCV system consists of:
^ Crankcase Ventilation Tube
^ Positive Crankcase Ventilation Valve
^ Crankcase Vent Oil Separator
^ Crankcase Pressure Relief Hose and Valve Assembly

PCV System Flow Schematic:

Typical PCV Valve:

Typical PCV Vacuum Connector:

The Positive Crankcase Ventilation (PCV) System cycles crankcase gases back through the engine where they are burned. The PCV valve regulates the amount of ventilating air and blow-by gas to the intake manifold and prevents backfire from traveling into the crankcase. The PCV valve should be mounted in a vertical position. On some applications, the PCV system is connected to the evaporative emission system (refer to the VECI decal).

CAUTION:
Do not remove the PCV system from the engine. Removal of the PCV system will adversely affect the fuel economy and engine ventilation and result in shorter engine life.