While we spend quite a bit of time discussing how to get our mowers moving and keep them running properly, we rarely think about the idea that at some point, our mower might decide to not stop running when we want it to. When this happens it can cause a bit of a panic – when they don’t run, you just have to figure out how to get it going. When they don’t stop you have a dangerous piece of machinery on your hands.
Bring it to an Immediate Stop
Once you’ve calmed yourself down and realized that your mower won’t cut off, you’ll want to kill the engine as soon as possible. If you know the engine is low on fuel, letting it out of gas is your safest bet. If you’ve got quite a bit left, you’ll need to open the hood or engine cover and use a wooden stick to pop the spark plug connector wire off of the spark plug terminal.
Make sure not to use anything other than a wooden stick, and it needs to be a dry stick – you are using it to break an electrical process, so you need to make sure that what you use will not conduct electricity.
Diagnose the Problem
The next step is to make sure that this doesn’t continue to occur.
If you have a mower with an ignition switch, that’s the best place to start. The most likely culprit is that the ignition switch is failing to ground properly. This is most likely due to poor connection. Clean the wires and connections, then try again, If it still doesn’t stop, you’ll need to replace the ignition itself.
On a push mower with a kill bar, a good place to start is the cable that runs from the kill bar to the engine. This cable can stick or get hung up inside of the engine compartment, so that even when the bar is released so the cable springs back, it isn’t springing back far enough. This causes the kill switch to fail to engage. Check the cable for corrosion, stretching, or notches. Lubricate or replace the cable.
In both types of mower, throttle issues can cause the engine to continue to run. The throttle feeds the engine, so if it sticks open, gas will continue to flow. Check and make sure that the return spring on the carburetor is not broken or weakened, and that the throttle body is properly lubed.
Checking these points will fix the problem 99% of the time. If you have gone through these steps and your engine still won’t stop when necessary, it’s time to seek professional help. Make sure to follow all safety precautions as you try and solve the problem, as the moving parts of a running engine can be dangerous.