Positive Crankcase Ventilation: Description and Operation

Crankcase Emission Control:

Crankcase Ventilation Valve:

PURPOSE
The crankcase emission control system vents crankcase gases back into the intake system.

OPERATION
The crankcase emission system is a closed system. No gases are vented to the atmosphere.

When manifold vacuum is low, the emission control valve opens fully to allow vapors to enter the intake manifold.

When intake manifold vacuum is high, the diaphragm in the control valve is pulled down, reducing vapor flow to the intake manifold.

An orifice in the control valve allows crankcase vapors to enter the intake manifold at idle and deceleration.

NOTE: When checking or adjusting CO content, disconnect and plug the control valve hose.