How to Fix a Lawnmower that Won’t Start

Lawnmower Won't Start

Spring is a wonderful time of year. The cold of winter is coming to a close and the trees and flowers are starting to show signs of life again. As the rain begins to fall and the sun shines more and more, your grass starts to grow. You look outside and decide that you need to mow your lawn. The only problem is that your lawnmower won’t start. No matter how mercilessly you pull the cord, all the mower does is sputter.

If your lawnmower won’t start, doing these things can help you get it running and prevent it from happening again:

  • Empty the gas before storing the mower
  • Clean or replace the air filter
  • Check the oil level
  • Start the lawnmower on a flat surface
  • Empty the old gas
  • Clean or replace the spark plug

Stubborn lawnmowers are a very common issue, especially if they haven’t been used for a couple of months. Although this is an incredibly frustrating problem, most of the time it is fairly easy to fix. Unfortunately, many people get rid of their lawnmower when it won’t start. I have seen people offer their lawnmowers for free online because it ran last season but won’t start now. They think something is horribly wrong with it, but all it needs is a few minutes of work.

Many times the work needed to get a lawnmower to start will take less time than unboxing and assembling a new lawnmower. All of the tools you will need can be purchased for very little money at your local hardware store. Here are a few things you can try to fix a lawnmower that won’t start.

Empty the Gas Before Storing Your Mower

Ben Franklin once said, “An ounce of prevention is worth a pound of cure”. This is true for many things, including lawnmower maintenance. One of the best things that you can do to avoid having trouble with a lawnmower that won’t start is to empty the gas out of it before you store it. Most people don’t mow their lawns very much, if at all, during the winter months. This means that the lawnmower could sit without being used for at least two or three months.

When the lawnmower sits for that amount of time, the gas becomes “stale”. While you should be able to store gas for up to two years without stabilizer, small engines can be a little finicky. This could be due to condensation mixing with the fuel as the mower sits. Because of this, it is a good idea to empty the gas out of the tank before you store your lawnmower for a long period of time.

Related: Build a Complete Prepper Tool Kit: Tool List and Tips

Clean or Replace the Air Filter

Lawnmower Won't Start
Be sure to clean your air filter before starting your lawnmower.

Before you even attempt to start your lawnmower, make sure that the air filter is clean. In order for the fuel to ignite, the lawnmower must be able to “breathe”. When a lawnmower has a dirty air filter, the amount of air flowing into the mower is greatly reduced.

Most of the time, you can clean the air filter by gently tapping it against a sidewalk or tree to remove most of the dust and grass trapped inside of it. If your filter is really dirty or damaged, you will need to get a new one. Just make sure you get the correct one. Look in your mower’s manual or online to find the correct filter. Also, take your old one with you when you go to buy a new one. You can compare it to the new one before you buy it as extra insurance you are getting the right part.

Check the Oil Level

Lawnmower Won't Start
The oil in my lawnmower is starting to darken. I will need to change it soon.

Another thing you should do before starting your lawnmower is to check the oil. Having a low oil level or dirty oil can cause the lawnmower to overheat. To do this, pull out the dipstick and wipe it off. Then, put the dipstick back in, close the cap, and then pull it back out. If the oil is above the dipstick’s fill line and has an amber color, then you are good to go. Add more oil if the oil has an amber color but is below the fill line.

If the oil is black, you need to change it. Before you do this, disconnect the spark plug wire to ensure the mower can’t start while you are working. You can empty the old oil using a siphon pump or using the mower’s drain plug. I don’t recommend tipping the mower to empty the oil because it is really messy and any gas that is in the mower will leak out. As you are emptying the oil, make sure it goes into an approved oil container. You can take the used oil to auto parts stores for disposal. After the old oil is removed, pour new oil into the mower.

Start the Lawnmower on a Flat Surface

Lawnmower Won't Start
Placing your lawnmower on a flat surface will make it easier to start.

If you are struggling with a lawnmower that won’t start, you will want to make the job as easy as possible. A good way to do this is to eliminate as much resistance as possible by attempting to start the lawnmower on a flat surface, such as a driveway.

When you pull on the lawnmower’s cord, you are basically performing a manual jumpstart. When you do this, the blade underneath the lawnmower turns. If the lawnmower is in tall grass, the grass will prevent the lawnmower blade from spinning. This makes the process much more difficult. When you place the lawnmower on a flat surface, you are drastically reducing the amount of effort it will take to pull the start cord.

Empty the Old Gas

Lawnmower Won't Start
Use a siphon pump to empty the lawnmower’s gas tank into a safe container.

If you left gas in your lawnmower over the winter, that may be the reason it won’t start. There are a couple of ways to remove old gas from your mower, but I prefer to use a siphon pump like this one. They are usually pretty inexpensive and are widely available at hardware and auto parts stores.

When using a siphon pump, one hose will go into the lawnmower’s gas tank and the other end will go into a separate container, like a gas can. Remove as much gas as you can by pumping the old gas from the lawnmower into the container.

After you have siphoned as much gas out of the lawnmower as possible, use a clean rag to wipe the inside of the gas tank. This will remove any remaining fuel as well as any condensation inside the tank. I like to wrap my rag around some long needle nose pliers to help me reach into as many areas as possible. When doing this, be sure to use a rag that won’t leave behind lint or fuzz balls.

After you have siphoned the old gas out of the tank and wiped it down, pull on the cord a few times to burn up any fuel that remains inside the lawnmower. After you have done this, you can pour your new gas into the gas tank without having to worry about it being contaminated by the old gas. I have used this process a few times, and it almost always works.

Clean or Replace the Spark Plug

Lawnmower Won't Start
A spark plug socket has a rubber insert to prevent damage to the spark plug.

If your lawnmower still won’t start even after all of the other steps, you need to take a look at your spark plug. To do this, unplug the spark plug wire. Then, use a spark plug socket and a ratchet to remove the spark plug from the lawnmower. You must use a spark plug socket. Using a regular socket could break the spark plug. After you remove it, inspect the gap of the spark plug. If there is any debris in the gap, remove it.

If your spark plug looks like it is cracked or burned, you need to replace it. Take your old spark plug to an auto parts store. They should be able to find a replacement based on the number on the spark plug’s body. Before you leave, be sure to inspect the spark plug to make sure it matches the old one.

Lawnmower Won't Start
Use a gap tool to adjust and measure the spark plug’s gap.

When you get your new spark plug, use a gap tool to set the gap to the proper size. This can be found online from the plug’s manufacturer. Once the gap is set, screw the spark plug in the mower, and tighten it. Be sure not to over tighten it, as this can damage the plug or your lawnmower. Reattach the spark plug wire and let her rip.


Hopefully, after completing these steps, your lawnmower will start and won’t have problems again for a while. Going through this process could save you from having to buy a new lawnmower or pay a bunch of money to have your lawnmower repaired.

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