5 Easy Fixes for a Lawn Mower That Won’t Start

If you can't get your lawn mower up and running, it's time to start troubleshooting. Chances are, one of these quick fixes will put it back to work.

By Tony Carrick and Manasa Reddigari | Updated Aug 13, 2021 11:17 AM

Lawn Mower Won't Start

istockphoto.com

Lawn care can be tedious, but once the grass starts growing in the spring, mowing becomes a fact of life in most neighborhoods. When you finally muster the strength to tackle that first cut of the season, there are few sounds as disheartening as that of an engine that turns over but doesn’t start.

Before you drag the mower in for repairs or invest in costly replacement parts, first make sure that a clogged air filter, soiled spark plug, damaged safety cable, clogged mowing deck, or contaminated gas isn’t to blame. Work through the following steps, and you may be able to get your puttering grass guzzler up and running again in no time.

Replace the Filter

Your lawn mower’s air filter guards the carburetor and engine from debris like grass clippings and dirt. When the air filter becomes clogged or too dirty, it can prevent the engine from starting. To keep this from happening, replace paper filters—or clean or replace foam filters—after every 25 hours of engine use.

The process for removing the filter depends on whether you are operating a riding or walk-behind lawn mower. For a riding mower, turn off the engine and raise the parking brake; for a walk-behind mower, pull the spark plug wire from the plug. Then, lift the filter from its housing.

The only choice for paper filters is replacement. If you’re cleaning a foam filter, wash it in a solution of hot water and detergent to loosen grime. Allow it to dry completely, and then wipe fresh motor oil over the filter, replace it in its housing, and power up the mower—this time to the pleasant whirring of an engine in tip-top condition.

Lawn Mower Won't Start

istockphoto.com

Tighten or Replace the Spark Plug

Is your lawn mower still being stubborn? The culprit may be the spark plug, which is responsible for creating the spark that ignites the fuel in the engine. If it’s loosened, disconnected, or coated in water or carbon residue, the spark plug may be the cause of your machine’s malfunction.

Locate the spark plug, often found on the front of the mower, and disconnect the spark plug wire, revealing the plug beneath. Use a socket wrench to unscrew the spark plug and remove it.

Check the electrode and insulator. If you see buildup, spray brake cleaner onto the plug, and let it soak for several minutes before wiping it with a clean cloth. Reinstall the spark plug, first by hand, and then with a socket wrench for a final tightening. If the problem persists, consider replacing the spark plug.

Replace the Dead Man’s Control Cable

Your lawn mower’s reluctance to start may have nothing to do with the engine at all but rather with one of the mower’s safety features—the dead man’s control. This colorfully named safety bar must be held in place by the operator for the engine to start or run. When the bar is released, the engine stops. While this mechanism cuts down on the likelihood of horrific lawn mower accidents, it also can be the reason the mower won’t start.

The safety bar of a dead man’s control is attached to a metal cable that connects to the engine’s ignition coil, which is responsible for sending current to the spark plug. If your lawn mower’s engine won’t start, check to see if that cable is damaged or broken. If it is, you’ll need to replace it before the mower will start.

Fortunately, replacing a broken control cable is an easy job. You may, however, have to wait a few days to get the part. Jot down the serial number of your lawn mower, then head to the manufacturer’s website to order a new cable.

Lawn Mower Won't Start

istockphoto.com

Clear Out the Mowing Deck

The mower’s deck prevents grass clippings from showering into the air like confetti, but it also creates a place for them to collect. Grass clippings can clog the mower deck, especially while mowing a wet lawn, preventing the blade from turning.

If the starter rope seems stuck or is difficult to pull, then it’s probably due to a clogged deck. With the mower safely turned off, tip it over onto its side and examine the underbelly. If there are large clumps of cut grass caught between the blade and deck, use a trowel to scrape these clippings free. When the deck is clean again, set the mower back on its feet and start her up.

Get a New Fuel Cap

The mower started just fine, you’ve made the first few passes, then all of a sudden the mower dies. You pull the cord a few times, but the engine just sputters and dies. What’s happening? It could have something to do with the fuel cap. Most mowers have a vented fuel cap. This vent is intended to release pressure, allowing fuel to flow from the tank to the carburetor. Without the vent, the gas fumes inside the tank begin to build up, creating a vacuum that eventually becomes so strong that it stops the flow of fuel.

To find out if this is the problem, remove the gas cap to break the vacuum, then reattach it. The mower should start right up. But if the mower won’t stay running and cuts off again after 10 minutes or so, you’ll need to get a new gas cap.

Fill Up the Tank

An obvious—and often overlooked—reason your mower may not be starting is that the tank is empty or contains gas that is either old or contaminated with excess moisture and dirt. If your gas is more than a month old, use an oil siphon pump to drain it from the tank. (It’s important to be careful as spilled oil can cause smoking. Check out this article to find out what to do if the lawn mower is smoking.)

Lawn Mower Won't Start

istockphoto.com

Fill the tank with fresh fuel and a fuel stabilizer to extend the life of the gas and prevent future buildup. A clogged fuel filter is another possible reason for a lawn mower not to start. When the filter is clogged, the engine can’t access the gas that makes the system go. If your mower has a fuel filter (not all do), check to make sure it’s functioning properly. First, remove the fuel line at the carburetor. Gas should flow out. If it doesn’t, confirm that the fuel shutoff valve isn’t accidentally closed. Then remove the fuel line that’s ahead of the fuel filter inlet. If gas runs out freely, there’s a problem with the fuel filter. Consult your owner’s manual for instructions on replacing the filter and reassembling the mower.

Assuming that one of these five fixes helped your mower run, a broken lawn mower is no longer an excuse to not mow. Go back out there and get your grass in shape for summer!

How’s your lawn care IQ? If you’re like many homeowners, you’re probably making one or two serious mowing mistakes. Take a look at our video to learn how you can improve your lawn care routine.

FAQs About Why Your Lawn Mower Won’t Start

If you’re wondering why your gas lawn mower won’t start or if you’re looking for tips for starting a lawn mower, then read ahead for answers to some popular questions. One of these answers may be exactly what you need to get your lawn in shape.

Q. Why is my lawn mower turning over but not starting?

The most likely reason is bad gas. Gas that sits for many months during the off-season will eventually break down, gumming up the fuel line and carburetor in the engine and preventing it from starting.

Q. How do you start a stubborn lawn mower?

If a mower is hard to start, it may be the result of a dirty carburetor and/or a clogged air filter. Use a screwdriver to remove the carburetor and clean any dirt out of it with a rag. Clean the air filter or replace it if it’s disposable.

Q. Why has my electric lawn mower stopped working?

The most common reason for an electric lawn mower to stop working is damage to the cord. Electric cords are typically pulled and flexed while the lawn mower is in use, which can cause damage to the inside of the cord, eventually preventing it from carrying the electric current needed to run the mower’s motor.

Final Thoughts

It can be extremely frustrating and backbreaking to repeatedly pull a lawn mower starter cord and then only hear the motor sputter and die. While your first instinct may be to haul the lawn mower off to the repair shop or even leave it by the curb for bulk trash pickup day, the mower may require only a simple repair you may be able to handle yourself. Before opening up your wallet, open up your tool box and give one these easy and cheap fixes a try.