Eagle L6-258 4.2L (1982)
Spark Control System: Description and Operation
Fig 36 EGR CTO Switches, 1973-81
Fig 37 EGR CTO Switches, 1982
On some models, vacuum spark advance operates on carburetor ported vacuum after engine has reached operating temperature. While engine is
warming up, driveability can be improved by operating the distributor vacuum spark advance with manifold vacuum while engine is cold. On
4-151 engines, the CTO switch is threaded into the bottom of the thermostat housing. On 6 cyl. models except Eagle, the CTO switch is located in
the heater hose CTO fitting on models less A/C and in the heater valve on models with A/C.
On Eagle models, the CTO switch is located at the left rear of the cylinder block. A thermal sensor switch is in contact with the engine coolant.
Depending on engine coolant temperature, the CTO switch, Figs. 36 and 37 will permit either manifold vacuum or carburetor ported vacuum to be
applied to the distributor vacuum advance unit.
On 4-151 engines, when coolant temperature is below 120 °F, manifold vacuum is routed through switch port 1 into port D allowing manifold
vacuum to be applied to the distributor vacuum advance unit.
On 6 cyl. engines, when coolant temperature is below 160° F on models except California or 165 °F on California models, vacuum is routed
through switch port 1 to port D allowing manifold vacuum to be applied to the distributor vacuum unit. On 4-151 and 6 cyl. engines, when coolant
reaches the specified temperature, port 1 closes and port 2 is connected to port D applying carburetor ported vacuum to the distributor vacuum
advance unit.
