Dear Sirs,
I have an old fashioned carburator on my boat and it seems that the choke is not operating. How does an electrical choke operate anyway??? Does the voltage( from primary side of coil) heat the spring element in the choke housing to make it expand and contract??? Or does it do this by turning the spring electrically by change in resistance as the engine warms up?? I am assuming that it knows when to choke or not by getting a voltage from the water temp. sensing unit. What happens to it from the sensing unit out?? There are two wires plugged into the center of the choke housing unit and it has a ground wire connected to one of the screws. Thanks, JoeA.

 

Electrical chokes were a simple device. The coiled element was a spring made from a bi-metal, two layers of different metals fused together. The spring action closed the choke so that when the engine was cold, it was choked properly. The bi-metal of the spring could expand and contract with temperature changes, winding and unwinding the spring. The purpose of this was to uncoil the spring and open the choke by passing an electric current through the spring coil to heat it, or heating an electric heater next to the spring. Generally, current was supplied when the ignition switch was turned on.

To work properly, first the choke must be set properly. Generally there were marks to which the choke housing (containing the spring element) was rotated and aligned with. Small adjustments could be made + or -. Then the electric choke element needs to be in good electrical condition. There needs to be continuity between the two side terminals which will show there is a good circuit through the spring or heater element and connecting wire(s) in the housing. Then the choke needs electrical power and a good ground.

 

Dear Mr. Formula,
How was the electrical choke told at what temperature the engine is?? Thanks JoeA