Choke Thermostat/Heater: Testing and Inspection

To determine the proper operation of the electric choke system, perform the following operational checks:

CHOKE VALVE AND FAST IDLE CAM OPERATION CHECK:

Fast Idle Cam: Normal Idle State:

1. Before starting the engine, the throttle valve should be in the normal idle opening state for cold engine operation and the engine coolant must be below 65~F (18~C).

Fast Idle Cam: Cold Idle State (After Pedal Is Depress):

2. Before starting the engine, depress the accelerator pedal to the floor, and the fast idle cam will turn clockwise. Release the accelerator pedal, and the lever will ride on the fast idle cam and the throttle valve will open.
3. When the engine starts, the intake manifold vacuum is applied to the choke breaker to slightly open the choke valve to the first stage position, preventing an over rich air-fuel mixture.
NOTE: When the engine temperature passes 65~F the thermovalve should close, supplying vacuum to move the choke breaker to the second stage position.

Fast Idle Cam: Cold Idle State (During Fast Idle Warm-up ):

4. Shortly after engine start, the bimetal spring is heated by its PTC heater and it expands to open the choke valve gradually, which pushes down the stopper lever. The stopper level is attached to the fast idle cam with a pivot and spring and does not move the fast idle cam, unless the throttle level is lifted to release the pressure on it. At this time the engine speed increases gradually.

Fast Idle Cam: After Fast Idle Kick-down:

5. Depress the accelerator pedal, to lift the throttle lever, and the fast idle cam will turn counterclockwise. Release the accelerator pedal and the lever will ride on a lower step of the fast idle cam closing the throttle valve slightly and decreasing the engine speed. After warming up the engine for awhile depress the accelerator pedal again and the throttle valve will be further closed. By repeating this procedure, the fast idle cam is released and the throttle valve comes to have a normal idle state.

CHOKE OPENER OPERATION CHECK:
To properly check the choke opener operation the engine coolant must be below 65~F (18~C) temperature.

Choke Opener Operation:

1. As the thermovalve closes, when the engine coolant temperature rises to 149~F (65~C ), the intake manifold vacuum acts on the choke opener.
2. The choke opener forces the fast idle cam to turn counterclockwise so that the lever will rest on the lowest detent of the cam, closing the throttle valve and decreasing engine speed.