Why Does My Lawn Mower Sputter When Blades Are Engaged?

Upgraded Home Team
by Upgraded Home Team

Lawnmowers, for many homeowners, are like a best friend. They’re tools we rely on! That’s why a sputtering mower can be a nightmare for people who get attached to their lawncare equipment.

If a lawnmower sputters when blades are engaged, the most common issues include low gasoline levels, damaged belts, stuck pulleys, and broken safety switches.

Though it’s common to worry about a favorite mower being “beyond repair” due to this issue, the truth is that most lawnmower problems are reparable—this one included. Here’s what you need to check for when you notice a sputtering issue.

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What Causes A Lawn Mower To Sputter?

Whether blades are engaged or not, there’s only one real portion of a lawn mower that can cause sputtering to happen. That area is the motor, which means that the reason for your mower’s malfunction lies somewhere in the motor.

How Common Is This Problem?

Generally speaking, seeing a motor that sputters out isn’t that uncommon. Though sputtering the moment blades engage is somewhat uncommon, it’s still not that unusual compared to other motor problems you could encounter.

The vast majority of these situations happen with mowers that are several years old or older. This often signals to people that it may be time to get a new mower.

The Most Common Culprits

Most lawn care experts note that a lawnmower that sputters and shuts down the moment blades are engaged has a motor that’s dying. In many cases, it boils down to one of four main issues.

Low Gasoline Levels

One of the less common (but easiest to fix) reasons why a motor might sputter out during its lawn trimming time deals with fuel. Many mowers are designed to sputter and shut down if there isn’t enough fuel to handle the work needed to cut the grass.

If you haven’t refueled your lawn mower recently, add some fuel before your mowing session. If that doesn’t work, then you might have a more difficult problem on your hands.

Bad Belts

Both tractor mowers and push mowers can have belts that go bad. Here’s what to do:

  • To check for this issue, lower your mower’s deck to the lowest setting and remove the belt guard. Referring to your mower’s manual can help you open it up.
  • If your belt is stuck, worn out, broken, or poorly routed, replace your belt. Your manual will show how to re-route a belt, if that’s the issue. If your belt shows signs of damage, you will need to order a replacement.

Broken Motor Safety Switches

Motor safety switches are there to help prevent serious accidents from happening. When the switch is tripped, the motor immediately gets the signal to shut down. It’s pretty clear how having a bad safety switch can cause a motor to sputter out when blades are engaged.

If you have reason to believe that the safety switch is the culprit, open your mower and check to see if the switch is properly plugged in. If it is, inspect it from damage. If it looks worn out, replacing it can fix the issue.

Broken or Worn Pulleys

Still not having much luck? Check your lawnmower’s pulleys, which should be located close to the belt. Much like the belt’s positioning, having poorly positioned or faulty pulleys can easily cause a motor to sputter the moment a mower hits grass.

The Less Common Culprits

Though “the Big Four” are the most common reasons for a sputtering motor, there are other causes that could make a motor run foul. Some of these causes can include…

Clogged Mower Parts

Sometimes, motors just get a lot of buildup from all the grass, mud, dirt, and grime they push through. Though there are measures to prevent grime from getting into key parts of your mower, it’s possible for grit to still show up from time to time.

Did you recently mow through some dust or some particularly sticky weeds? In many cases, thorough cleaning of the mower can get rid of the stalling and sputtering problems you’re experiencing.

Dirty Air and Fuel Filters

In a lot of ways, troubleshooting a mower is a lot like troubleshooting a car. In both cases, people tend to forget how important it is to keep filters maintained. Those filters aren’t just for keeping things environmentally friendly; it’s also a matter of ensuring that your mower can run.

Though it’s rarely the primary reason why motors die, it can be a contributing factor.

Improper Use

If you’ve been using your lawn mower regularly for the past couple of years, it’s safe to rule this potential cause out. However, if you are new to a mower, it could be that you’re operating it in a way that triggers an automatic shutoff or that places undue stress on its motor.

When Should You Call In A Professional?

It’s worth pointing out that most lawn mower problems are fixable, so there’s no need to buy a new mower if you don’t want one. However, not all mowers are going to be fixable on a DIY basis. If any of these are true, you may need professional help:

  • You tried all the troubleshooting tips and you still have trouble keeping your mower on. If you’ve already tried everything you can think of, asking for some additional help could be the only way you can get it fixed.
  • There’s something caught in the mower that you can’t remove on your own. This can happen, and when it does, having a pro look at it is the best move. It’s better to pay a professional to remove it rather than pay for a new mower if you break it.
  • You hear an alarming grinding or squealing noise when your mower sputters. This suggests that the actual gears in the motor could be dying. Replacement might be necessary if it’s not professionally fixable.
  • The mower that you have is heavily computerized. Several professional-grade mowers are now equipped with computers that control the lion’s share of the mower’s functions. If it’s a computer or electronic issue, you will not be able to fix it without taking it to a professional shop.
  • Convenience is an issue. If you don’t have the time to fix it, getting someone else to do it for you just makes sense.

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Our Final Take

Having a lawnmower that sputters out the moment blades start being put to use is annoying, but it’s a common and fixable issue. We wrote a guide about what to do when your mower’s blades won’t engage.

In most cases, you can expect it to be an issue involving maintenance, belts, safety switches, pulleys, or just a clogged mowing area. Most of these causes can be easily fixed through DIY repair means—if you want to fix it.

However, there’s always a chance that it could be a more advanced problem. If your troubleshooting hasn’t worked out, or if you notice additional problems that require attention, calling a professional is a smart move.

Of course, it’s worth pointing out that many people take this as a sign that it’s time to start looking for a new mower. So, if you’re not too attached to your mower, maybe it’s time to check out what new models would work for your home’s needs.

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Upgraded Home Team
Upgraded Home Team

We are a team of passionate homeowners, home improvement pros, and DIY enthusiasts who enjoy sharing home improvement, housekeeping, decorating, and more with other homeowners! Whether you're looking for a step-by-step guide on fixing an appliance or the cost of installing a fence, we've here to help.

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