Lawn Mower Won’t Start? Try These 8 Troubleshooting Tips

Uh oh. It’s finally the day you go to mow your lawn, and your lawn mower won’t start. What now? Before you rush out to buy a new mower or get used to the idea that your lawn is doomed to grow wild forever, try a little troubleshooting. Lawn mowers—whether they’re riding mowers or smaller push models—tend to have the same common problems. Most of the time, there’s an easy solution with an inexpensive fix. Here are some reasons and solutions for a lawn mower that won’t start.

How to Troubleshoot a Lawn Mower That Won’t Start

Once you start looking, you’ll probably find some clues as to why your lawn mower won’t start. Most of the time, you can solve the issue with a simple tune-up costing between $60 to $250.

1. Check the Gas Tank

If you leave your lawn mower outside or are pulling it out of its winter retirement, you may notice that the fuel has become contaminated with rainwater. To check the fuel tank:

• Examine the fuel level. Is there enough gas in the tank?

• Look to see if there are bubbles of water floating in the fuel (these are usually apparent on the bottom of the tank)

• If you’re still not sure, drain a little bit of fuel and check for water

• If you see signs of water, drain the old fuel completely, dry out the tank using compressed air, and refill it with new fuel

Make sure to detach your spark plugs so your mower can’t accidentally start while you’re checking it over. To prevent this problem in the future, store your lawn mower properly.

2. Check the Fuel Filter

If fuel isn’t reaching the engine’s combustion chamber during the ignition process, your lawn mower won’t start. Sometimes you can tap the side of the carburetor to push the fuel along. If that doesn’t help, swap out the fuel filter.

3. Test the Battery

Some lawn mowers (like electric riding mowers) use batteries. Similar to a car battery, it will degrade over time and struggle to hold a charge. You’ll eventually need to replace it, though most batteries last three to five years. If your mower won’t start, check the battery by:

• Looking at the headlights (dim headlights mean your battery is on its way out)

• Visually inspecting the battery for cracks, corrosion, and other damage

• Testing the charge with a device called a multimeter

4. Check the Oil Level

Lawn mowers need oil just like cars—and that oil can also become contaminated with rainwater. If your lawn mower won’t start, check to make sure you have enough oil. If the oil has turned milky white, it’s a sign that water has contaminated it. 

5. Check the Spark Plugs

Faulty spark plugs are one of the most common reasons a lawn mower won’t start. They can become loose, dirty, disconnected, or worn out. Before reaching for a replacement, clean and tighten the old plugs to see if it fixes the problem. You can usually find them on the back or side of your mower engine. 

6. Clean or Replace the Air Filter

Always check the air filter while troubleshooting. The manufacturer manual should tell you where to locate the filter. If it looks dirty, remove the air filter and try to get rid of some of the buildup. If that doesn’t work, replace it altogether.

7. Raise the Height of Your Mower

Has your mower ground to a halt? It might be tripped up by too-tall grass. Always adjust your mower height if you’re trudging through patches of tall grass, and make sure to cut grass to the correct height.

8. Clean the Underside of Your Mower

Sometimes the starter rope on your mower gets stuck or becomes really hard to pull. In this case, it could be an issue with your flywheel break or debris stuck in the underside of your mower. To check for debris:

1. Turn off your mower engine

2. Disconnect your spark plugs (for safety)

3. Examine the blade for debris

4. Remove dirt, grass cuttings, and anything else potentially stuck

If that doesn’t fix your problem, your mower may need a more serious repair.

When to Call a Professional

At the end of the day, the reason your lawn mower won’t start could be a problem that you can’t fix on your own. You might need a brand new part (like a starter motor), or you may have to go deep inside the engine to make a repair. These are not the best candidates for a DIY fix. 

Mowers have sharp blades. Their construction is highly technical. They’re heavy machinery—especially a riding mower. Attempting to fix issues on your own can be dangerous. The good news is that most homeowners with a small walk-behind mower pay less than $250 to have a professional repair their machine. 

If regular troubleshooting didn’t solve your issue, take your lawnmower to a local lawn mower repair shop. You can hire a local lawn care service to mow your grass in the meantime.