House Grail is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Why Won’t My Lawn Mower Start After Sitting? 11 Possible Reasons

man checking lawn mower battery

A lawn mower is an important tool for maintaining your lawn, but its many moving parts can wear out and cause it to be difficult to start, especially after sitting for several months. If you are having trouble with your mower, keep reading as we look at several factors that can be causing it and explain what you can do to get it running again.

divider 4

How Does It Work?

A lawn mower is a fairly simple device that houses a long blade inside the deck or body of the machine. An engine on the top of the machine spins the blade quickly so it can chop the grass as you push it. Many machines enable you to adjust the blade’s height and the speed that it rotates. Some will use the engine to add a self-propelling feature, and others will dispense the clippings into an attached bag or mulch it into fine particles so it can add nutrients back into the lawn. Other features can include an electric starter, an electric motor, and more.

What Are the Different Types of Lawn Mowers?

gas and battery powered lawn mower in the garden
Image Credit: Sergey and Marina Pyataev, Shutterstock

The most common type of mower is the walk-behind mower, which you push over the grass to cut it. Another type is the riding lawn mower, which allows the user to sit and ride it like a tractor. Several brands make electric walk-behind mowers that you need to plug into an outlet while you use them, and rechargeable battery-powered mowers are also becoming popular.

divider 1

Walk-Behind Mowers

Where Are They Used?

The walk-behind push mower is extremely common, and you can find it maintaining lawns of residential homes anywhere in the world. While riding lawn mowers are becoming more popular, the walk-behind mower is still the king.

Advantages of Walk-Behind Lawn Mowers

man using lawn mower
Image Credit: Roman Zaiets, Shutterstock

Walk-behind lawn mowers are relatively inexpensive and easy to use. The powerful gasoline engines have more than enough power to cut through dense vegetation, and they often last many years before you need to replace them. These mowers are lightweight and easy to control, and many have a self-propelling feature that takes out much of the work of pushing them. Many also have bags to catch the clippings, so you don’t need to rake afterward.

Disadvantages of Walk-Behind Lawn Mowers

The primary downside of walk-behind lawn mowers is that most start by pulling the starting cable, which can be difficult for many people. It puts a great deal of strain on the back, and some people just don’t have the strength to pull it hard enough to start the motor. Another disadvantage of these mowers is that you have to push them, so a large property can require several miles of walking to get all the grass.

divider 7

The 11 Reasons Your Lawn Mower Won’t Start After Sitting

1. No Gas in the Tank

You might be surprised at how many people forget to check how much gas is in the tank before they try to start it! Luckily, this is an easy fix, as you will just have to add more fuel to get it going.

2. Bad Gas in the Tank

Gas can go bad if you let it sit too long without adding a stabilizer. If you forgot to do so, there is a good chance that the gas is no longer good. Bad gas will not fire properly, preventing you from starting the mower. You will need to pour the bad gas out of the machine carefully into a suitable container and take it to your local recycling plant to dispose of it. Refill the tank with fresh gas, and add a stabilizer to help keep the new gas fresh and clean out any contaminants that the old gas left behind.

3. Clogged Fuel Cap

A clogged fuel cap won’t allow air to enter the tank as you use the fuel, which will create a vacuum that restricts fuel flow, causing the machine to stall. If you didn’t check your tank to see if you have fuel, there might still be a vacuum in the tank preventing the gas from reaching the engine, so it won’t start. To fix this problem, you can either replace the cap or use a thin wire to clear the clogged holes.

4. Bad Spark Plug

Replacement of the spark plug of lawn mower_Alexsander Ovsyannikov_Shutterstock
Image Credit: Alexsander Ovsyannikov, Shutterstock

The spark plug in your lawn mower takes a great deal of abuse, so you should change it frequently. If it’s been a while since you changed it and you’re having difficulty getting the mower started, it might be time to replace the spark plug. Remove it with a pair of pliers or a socket wrench, and take it to your local auto parts store to get a new one.

5. Clogged Air Filter

The clogged air filter will prevent air from reaching the engine, and the gas won’t be able to fire to start the engine without oxygen. If you think that the air filter is clogged, you can clean it using dish soap and warm water. If that doesn’t work, you must purchase a new one to run the machine.

6. Clogged Fuel Filter

A clogged fuel filter can prevent fuel from reaching the engine, causing it not to start. Unfortunately, you cannot clean the fuel filter, so you will need to replace it to get the motor running again.

7. Bad Fuel Pump

The fuel pump pumps the gas into the engine, and if it fails, the engine will stall and will not start again until you replace the fuel pump.

8. Blocked Fuel Lines

man fixing lawn mower engine
Image Credit: Douglas Cliff, Shutterstock

A blocked fuel line isn’t as common as some other issues on this list. However, if you recently found bad gas in your mower, it’s a real possibility because bad gas tends to gel and can easily clog a fuel line. To clear it, you can remove the gas line and use compressed air or a carburetor cleaner to blow it out.

9. Dirty Carburetor

A dirty carburetor is a common reason that many lawn mower engines won’t start. Contaminants from the fuel buildup in this area can prevent fuel flow, causing the engine to stutter and be hard to start. The best way to remove the contaminants is to use a carburetor cleaner to get them out.

10. Bad Battery

If your mower has a battery, it can be difficult to start it if it goes dead. Loose connections and corroded terminals can also cause starting problems. Charge the battery, or replace it if you find that it won’t hold enough charge to get the mower running again.

11. Bad Starter or Coil

If your lawn mower has electronic ignition, there’s a chance that the component went bad and will need replacing before you can get the machine started. Even mowers that require you to pull the starting cable will use a coil to start the motor that can go bad.

divider 1


The most common reason that a lawn mower might not start after sitting a while is that the gas went bad because a stabilizer wasn’t added before the mower was stored. You’ll need to empty the gas and replace it to get it running again. Other common issues include a dirty carburetor and a bad spark plug, so we recommend starting there. After eliminating those problems, you can go down the list until you find the real problem and get your machine running again.

Featured Image Credit: ALPA PROD, Shutterstock


Related posts

OUR categories

Project ideas

Hand & power tools