When a mower is working correctly, releasing the bail lever turns off the mower. If your mower doesn’t have a bail lever, then the throttle lever doubles as the on-off control. However, a mower that just won’t turn off is actually quite common, the solution is usually simple, but first, we’ll need to kill the engine.
So, how to turn off a lawnmower? The fastest way to turn off a mower that won’t stop is to remove the spark plug wire. The wire carries voltage, so you’ll need insulated pliers.
Other options include:
- Apply Full Choke
- Turn Off Gas Tap
Most mowers come with what’s known as the dead man’s lever, you may know it as the Bail lever and as you know you must hold it to start the mower and release it to shut it down. Check out “How to start / stop a lawn mower”. The dead man’s lever doesn’t give much trouble, but if the wiring has come loose at the engine, the mower may not shut down.
Other mowers may simply employ a cable-operated lever to turn the mower on/off. These types of controls are usually fitted to mowers that also have a blade engage control lever. Anyway, I’ll show you three options to shut off your mower, and then we’ll take a look at what could be causing the problem.
Bail Lever – Releasing the bail lever kills the engine.
Stop/Start Lever – Move the lever to stop position kills the engine.
Shut Down The Engine
You have three options to shut down a mower with a faulty on/off switch. The fastest way by far is to pull the plug wire, but wow, not so fast, you’ll need a pair of insulated pliers.
The other options work for most mowers, but they may flood the engine with gas and so the engine might not restart for 30 minutes or so until it dry’s out, but it won’t hurt the engine any.
Choke – Apply full choke, this will cause the engine to get too much gas and it will likely stall.
If your mower has an auto choke or a primer bulb you won’t be able to apply the choke manually so instead remove the air filter cover and air filter.
Using a clean cloth, cover the mouth of the carburetor, this restricts airflow and chokes the engine.
Gas Tap – Most lawn mowers will have a gas tap, it lives usually beside the carburetor and when turned to the off position, kills the gas flowing to the engine. Need help finding your gas tap, click here.
Turning the gas off won’t take effect right away, it may take a minute or two before the engine starts to stumble and eventually stalls.
If you don’t have a tap, you can stop fuel flowing to the carburetor by pinching the gas line with pliers or vice grips.
Plug Wire – The plug wire carries voltage and will shock if you just grab it, it’s not enough to kill you but if you have a heart complaint it could. It’s quite safe to pull the plug wire while using plastic-handled pliers.
The plug wire is a push-on pull-off fit and is pretty easy to remove, sometimes, however, they can be on pretty tight, so twisting while pulling helps. Be mindful, the mower will move towards you if not secured, you don’t want your toes going under the deck.
Be smart about this, move the mower so that the front wheels face a wall, then yank on the wire.
Why Won’t The Engine Turn Off?
Faulty wiring is the common reason a mower won’t shut down, the wiring as you expect is simple. Banging into fences and cutting under hedges and shrubs can cause small components to come loose.
Other common causes include:
- Loose wiring
- Cable out of adjustment
- Faulty flywheel brake
- Faulty on / off switch
How’s it Work?
The coil and flywheel create the energy that the plug needs to fire. At its simplest – the positive charge travels from the coil through the plug wire to the spark plug. The positive energy is always looking for the shortest path to negative/ground (engine casing), and since its only option is to jump the spark plug gap, it does so and creates a spark in the process.
But if you offer the coil a more direct path to negative/ground it will bypass the spark plug and send the voltage to the ground instead. This is exactly what happens when you switch off the mower. The most common reason the mower won’t shut down – the small single ground wire has become detached or is making poor contact. The mower will run just fine without this wire, it just won’t shut off.
Look for any obvious signs of loose wiring, you might find this post helpful “Toro won’t shut off”.
Spark – Voltage passes down the plug wire through the plug and jumps the gap causing the spark. If the coil is given a more direct path, it won’t travel down the coil wire to the plug.
Turning the mower off offers the coil a shorter path, it does this by connecting a ground wire to the coil.
Lever On/Off Switch – The Bail lever is a common way to turn off a mower engine. It has 4 components bail lever, cable, brake assembly, and on/off switch.
Other mowers may have a throttle lever and stop-start unit combined. These types of setups will have a cable that will need adjustment from time to time.
Brake Assembly – When the bail lever is released or throttle lever set to stop, depending on which type you have, a brake is pressed against the flywheel and a direct ground path is given to the coil through a switch and or single wire.
This, as you know, stops the flow of volts to the spark plug, if it’s disconnected it won’t divert voltage and so your engine won’t turn off.
The black switch seen here with a single wire push-on the connector is the on/off switch.
How does a small engine kill switch work? The small engine kill switch sends the coil a direct path to the ground. The stored voltage in the coil is then discharged, instead of firing the plug. To start the engine, the kill switch simply takes away the coil path to the ground.
How do I start my lawnmower with a choke? First, check the oil and make sure the gas is fresh.
- Check gas level
- Put choke full on
- Pull start engine
- When running, move choke to half
- After 30 seconds turn choke off
- About the Author
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John Cunningham is an Automotive Technician and writer at Lawnmowerfixed.com.
He’s been a mechanic for over twenty-five years and shares his know-how and hands-on experience in our DIY repair guides.
Johns’s fluff-free How-to guides help homeowners fix lawnmowers, tractor mowers, chainsaws, leaf blowers, power washers, generators, snow blowers, and more.