F 250 4WD Pickup L6-300 4.9L (1982)
Electric Assist Choke: Description and Operation
Fir. 38 - Typical Electric Assist Choke Installation
Fig.39 - Electric Assist Choke Wiring Schematic
Purpose
Most 1973-82 models are equipped with an electric assist choke to reduce hydrocarbon (HC) and carbon monoxide (CO) emissions during starting
and warm-up--choke on--period.
The electric assist choke is designed to give a more rapid choke opening at temperatures of about 60° to 65° F, or higher. It also provides a slower
choke opening at temperatures below this point.
Operation
Current is constantly supplied to the ambient temperature switch. The system is grounded through a ground strap connected to the carburetor body.
At temperatures below approximately 60 degrees, the switch opens and no current is supplied to the ceramic heater located within the thermostatic
spring. Normal thermostatic spring choking action then occurs.
At temperatures above approximately 60-65 degrees, the temperature sensing switch closes and current is supplied to the ceramic heater. As the
heater warms, it causes the thermostatic spring to pull the choke plates open within 1-1/2 minutes.
The electric assist choke system does not change any carburetor service procedures and cannot be adjusted.
