Wagoneer L6-258 4.2L VIN C 2-bbl (1982)
Spark Control System: Description and Operation
Dual Range Coolant Temperature Override (CTO) Valve
PURPOSE
This dual function valve replaces the function of the standard CTO valve until a specified coolant temperature has been reached, causing the valve
to switch ported vacuum back to manifold vacuum. The dual range CTO valve is installed in the same location as the standard valve.
OPERATION
When coolant temperature is below 149° F, manifold vacuum is routed through port 3, into port 2, allowing manifold vacuum to be applied to the
distributor advance unit. This improves warm-up driveability by providing full vacuum advance until coolant temperature reaches 149° F.
When coolant temperature is between 149° F and 220° F, port 3 closes and ports 1 and 2 are opened. Manifold vacuum is blocked and carburetor
ported vacuum is applied to the distributor advance unit. When coolant temperature reaches 220° F, port 1 closes and ports 2 and 3 open, applying
manifold vacuum to the distributor advance unit. Engine idle speed will now increase and engine cooling efficiency is improved.
