Chain Saw: Can't Turn Engine Off

Like the ignition and kill switches, the lever in your chainsaw actuates the ignition switch to create or interrupt a circuit, which allows the chainsaw to run, and to shut off. When the ignition switch is set to the “on” or “run” position, the circuit remains open; no current is flowing through the switch. When you want to turn the engine off, the ignition switch is set to off, or a kill switch is depressed. This creates a circuit from the ignition coil straight to engine ground. Now, the circuit is grounded, and the spark plug no longer fires. This will cause your chainsaw to shut off. If your chainsaw will not shut down when the ignition switch is set to off, or the kill switch is engaged, and your chainsaw still won’t turn off, it could be the result of an issue with the lever. If the lever becomes damaged or malfunctions during operation, it will not allow the engine to turn off. A damaged lever may also result in your engine being unable to turn on, if the damage occurs while the machine is not running.

The ignition switch is turned on or off to control the ignition circuit. However, if your engine relies on the ignition switch to complete the circuit and shut down the engine, a damaged switch can cause the engine to run and not turn off. In either setup, the switch can still cause this symptom. If the switch is an on/off type, it will create a circuit to ground when it is off. When the switch is on, current will flow to the spark plug because the circuit is open. In a kill switch setup, the switch is normally not creating a circuit, which allows the engine to start and run. When you want to shut the engine off, the switch is depressed and held. This creates a circuit to ground which shuts off the engine.

The kill switch or ignition switch in your chainsaw are connected by wires, and if one of these wires is damaged or malfunctioning, it can prevent you from turning the engine off. When the wires break, it will typically occur at the connection to the switch or the ignition coil. As mentioned in our sections on levers and switches, a bad connection will not allow the circuit to be created or interrupted, and therefore you will not be able to shut down the chainsaw. If you have bad wiring, it will need to be replaced before this symptom is resolved.