Riding Mower Stalls When Blade is Engaged: Why + How to Fix

You jump on your riding mower, fire it up and flip the lever to engage the blades and…NOTHING. The engine stalls. And it does that over and over again.

That’s obviously no good and can get old pretty quickly. But you’ll be glad to know that if your riding mower stalls when the blade is engaged there is often a simple explanation.

I’m going to talk you through a few of the most common causes of this problem and how you can fix it.

Riding Mower Stalls When Blade is Engaged: Common Causes

There are a few things that I’d recommend you check if your riding mower stalls when the blade is engaged, some more involved than others.

Something Stuck in the Blade

This might seem like a painfully obvious reason for your riding mower to stall, but it’s easy to overlook given you actually can’t see what’s going on in the deck unless you get off your mower and lift up the hood.

If you’ve got something particularly large in there, like a large stick or part of a branch, your blade isn’t going to go anywhere.

And if the blade isn’t able to move, the mower’s motor will come under more and more strain, trying its best to break the blade free, but when it can’t, it’ll stall.

This video highlights this issue perfectly:

 

Solution: All you need to do to fix this is to carefully remove the obstruction. Make sure your mower is definitely shut off and the blades are not set to “engaged” before you do anything.

You might need to use a small jack to lift one side of your mower up to make the obstruction easier to get at.

Safety Switch Under Seat Faulty/Not Properly Connected

There are a few different safety switches on most riding mowers. They’re designed to protect you against accidental injury, but when they’re not working properly, they can cause problems.

There’s one such safety switch located under the seat. It detects when you’re actually sat on the seat, and deems that it’s safe to engage the blades.

But when you step off your riding mower, this switch detects that and won’t let you engage the blades.

The reason being, if you’re off the mower and the blades are engaged, you could potentially be fiddling around with the deck and hurt yourself.

However, if this switch is faulty or the connection is loose, it may stall when you try to engage the blades even if you’re sitting on the seat. It’s simply not detecting that you are.

Here’s a good video to illustrate this:

 

Solution: You can access this sensor by lifting up the seat on most riding mower models.

The first thing would be to pull it out of the connection and then blow on it. It could be dust or dirt causing the problem.

Plug it back in and see if that fixes the issue. If it doesn’t, you might need to replace this switch.

Bent/Damaged Spindle Pulleys

Your riding mower relies on a series of spindle pulleys and a drive belt to turn the blades.

If you’ve ever had problems with either of these parts – a mower deck belt that keeps coming off, for example – you’ll know both how vital they are and what a pain in the ass they can be when something goes wrong.

If any of the spindle pulleys are bent out of shape or are not spinning properly, the belt won’t be fed around the deck properly, and this could cause the engine to stall.

If your belt has been coming off frequently or worse yet, your lawn mower belt keeps breaking, this is a pretty clear indicator that something is wrong, and the pulleys need to be checked out.

Solution: Shut your riding mower off completely and raise the deck or disconnect it and remove it.

You need to be able to get at the pulleys to test them. You’ll also need to remove your mower belt for this.

Sometimes damage will be obvious at a glance. But you should work your way around the deck and test each of the pulleys to make sure that they’re spinning correctly.

If you find that any of them are damaged, they may need replacing.

Exposed Wiring

If any of the electrical wiring that’s used on your riding mower has had the insulation worn off and this comes into contact with metal, it will ground out the engine and cause it to stall.

As you’re having issues with the mower stalling when the blade is engaged, it might be worth checking any wiring that this lever could come into contact with.

Solution: This will require you to play the role of detective and may take a bit longer than some of the other fixes that you’ll find on this list.

As I just mentioned, I would start by looking for any wiring that could come into contact with the blade engagement lever.

If you do find any exposed wiring, cover it up with some electrical tape.

You Need a New Battery

If a riding mower stalls when the blade is engaged, one of the most overlooked things is to check on the condition of the battery.

Lots of people get fixated on the fault being mechanical, but as you can tell from this list, it can often be electrical.

If you’ve had the battery for a good length of time and it’s shown signs of struggling in the recent past (maybe issues with slow starting), it may be causing the engine to stall when you engage the blades.

Here Rob Douthit explains this issue very well:

 

Solution: The solution here is very simple; you need to buy a new battery. It’s also worth asking a pro what the recommended battery is for the specific riding mower model that you have.

It could be that your current battery was already underpowered (fewer cold cranking amps) and that has further compounded the issue.