Why Does My Lawn Mower Shut Off When The Blades Are Engaged?

Thanks to modern lawn mowers, yard maintenance has become a manageable weekly chore. Unlike the old days when people would trim grass using a scythe, this machine allows you to cut grass without breaking your back.

A lawn mower is the ultimate time-saver for gardeners. It can be a significant investment, but it’s worth the price. There’s nothing like relaxing in your garden surrounded by perfectly manicured grass. A lush, green lawn is also guaranteed visitors and neighbors alike.

But what if your lawn mower suddenly stalls when the blades are engaged?

Don’t be too hasty in getting a replacement. Check out these common reasons why your lawn mower bogs down while cutting grass.

Why Does My Lawn Mower Shut Off While Mowing?

Fuel Problems

When did you last fill up your fuel tank? If you have an empty or near-empty fuel tank, don’t be surprised if your lawn mower suddenly dies in the middle of yard work.

It takes less than a month for fuel left inside the tank to deteriorate. This “bad” fuel will become a sticky residue that clogs up the fuel filter. Make sure you replace any long-standing fuel and clean the fuel filter regularly.

Loss of Air

Going through tall or thick grasses can cause lawn mower engines to stall. If your lawn mower suddenly sputters on the job, check if the engine has enough airflow. Fuel can’t combust without sufficient air, so your lawn mower loses power.

Make part of your yard maintenance routine to clean the air filter thoroughly. It should be free of grass, dust, and other debris.

Faulty Carburetor

A lawn mower’s carburetor is responsible for setting the rate of your mower’s fuel consumption. Carburetors need frequent adjustments to ensure that the amount of fuel matches the engine speed. Adjusting carburetor screws has a significant impact on your engine, so it is best left to the professionals.

Similarly, your carburetor might need a thorough cleaning. Any impurities can block the carburetor and stop a lawnmower in its tracks.

Faulty Carburetor

Damaged Switches

Another possible reason why your lawn mower loses power is a faulty safety or power takeoff (PTO) switch.

Your lawnmower has safety switches designed to shut the mower automatically in case a roll-over happens. This prevents the operator of the machine from getting seriously injured by the mower’s blades.

How do I know if my PTO switch is bad? Check if the safety switch is securely plugged in. This switch is located under the seat. If it is broken, then you would need to have it replaced. Consult a professional for this sort of issue.

The repair shop will pull out the switch and see if it is broken. They may use a multimeter to go through the wiring for a possible short.

If your engine dies when the PTO is engaged, a weak battery or a faulty clutch may also be at fault.

Pulley Issues

The engine’s drive belt drives its crane and cranks, which in turn rotates the spindles. If your pulley is unable to spin completely, your engine will likely die every time the blades are engaged.

Getting into the mower deck and manually testing the pulley can help you identify the issue. A piece of debris or accumulated grass might be interrupting the cycle. Since the pulley is a moving part, it may have become warped or broken over time. This one reason why your riding lawn mower shuts off when its blades engage.

Incorrectly Routed Belt

You also need to see if your belt is improperly routed. Depending on your lawn mower’s make and model, you must consult the owner’s manual to verify the correct routing. Rerouting the lawn mower belt can resolve this issue.

When Should I Get My Lawn Mower Serviced by a Professional?

When your lawn mower fails to work properly, you have the option of either DIY troubleshooting or taking your machine to a repair shop. Which is the best option?

If you are mechanically inclined and have the time to do repairs, you can solve simple lawn mower issues yourself. Cleaning the air filter or blades, replacing parts, changing the oil, and refueling can all be done at home.

For your safety, you should consult an expert for more serious issues like:

  • smoke coming from the engine
  • severe vibrations
  • unusual noises coming from the engine
  • oil leaks or black exhaust fumes
  • excessive fuel consumption

Consulting an expert can also help you save money and time, as you are assured that the problem will get fixed the first time around. Your warranty may also require you to get the machine serviced according to a set schedule.


Now, you have a better idea why your lawnmower is shutting off when the blades are engaged. Hopefully, these pointers will allow you to identify the problem quickly and reach a solution that won’t break your budget.