The carburetor switch is located at the end of the antidieseling solenoid. The primary purpose of the switch is to inform the computer when the engine is at idle or off-idle. When the carburetor switch is closed at idle, the computer cancels the spark advance and the idle control circuit adjusts the air/fuel ratio.
Grounding carburetor switch eliminates all spark advance on most systems.Switch
- With ignition key in OFF position, disconnect 10-way connector from Spark Control Computer.
- With throttle completely closed, check continuity between pin 7 of disconnected 10-way connector and a good engine ground. Continuity should exist.
If continuity does not exist, check the wiring between the ESC computer and carburetor switch.
If continuity does exist, proceed to the next step.
- With throttle open, check continuity between pin 7 of disconnected 10-way connector and a good engine ground. There should be no continuity.
- If the switch fails to perform as specified, replace the switch and retest.
Antidieseling solenoids are also referred to as "throttle stop" or "idle stop" solenoids.
- Turn the ignition key ON and open the throttle. The solenoid plunger should extend (solenoid energized).
- Turn the ignition OFF . The plunger should retract, allowing the throttle to close.
With the antidieseling solenoid deenergized, the carburetor idle speed adjusting screw must make contact with the throttle shaft to prevent the throttle plates from jamming in the throttle bore when the engine is turned off.
- If the solenoid is functioning properly and the engine is still dieseling, check for one of the following:
- High idle or engine shut off speed;
- Engine timing not set to specification;
- Binding throttle linkage;
- Too low an octane fuel being used.
Correct any of these problems, as necessary.
- If the solenoid fails to function as outlined in Steps 1-2, disconnect the solenoid leads; the solenoid should be de-energized. If it does not, it is jammed and must be replaced.
- Connect the solenoid to a 12V power source and to ground. Open the throttle so that the plunger can extend. If it does not, the solenoid is defective.
- If the solenoid is functioning correctly and no other source of trouble can be found, the fault probably lies in the wiring between the solenoid and the ignition switch or in the ignition switch itself. Reconnect the solenoid when finished testing.