Depending on the size of your lawn, having a riding lawn mower is essential to keep your space tidy. However, if your sit-on lawn mower won’t start fixing the issue could take some time. Luckily, I have made a simple-to-follow guide on finding the problem and repairing it to help you get back to mowing as soon as possible.

There are eight main categories why your riding lawn mower might not start. These categories include the following:

  1. Fuel problems
  2. Faulty spark plugs
  3. Oil problems
  4. Malfunctioning battery
  5. Problems with the air filter
  6. Choke problems
  7. Problems with the ignition switch
  8. Operating procedures

Though the more common problems with starting your riding lawn mower can be placed into just eight categories, there are many things you need to consider. The process might take some time, so following a list could help you find the solution to your problems.

If none of the explanations can help you, you might need to consider calling a professional.

Riding Lawn Mower Won’t Start – Possible Causes

As seen in the list given above, there are plenty of reasons why your riding lawn mower might not be starting. Below are the most common reasons placed into sections to simplify the process of troubleshooting.

Fuel Problems

There are numerous reasons why your riding lawn mower might not start because of fuel.

Two of the most commonly found issues are that the lawnmower is out of fuel or that the fuel is too old or the wrong kind. These problems are usually easy enough to solve.

  • Out of fuel. As with any other machine that uses fuel, it is essential to check the fuel levels now and again. Ensuring that your riding lawnmower has gas is naturally the first step to determining why it won’t start.
  • Wrong or old fuel. There are different types of fuel on the market today, which is why making sure you have the right sort of fuel for your lawnmower is essential. Most riding lawn mowers use unleaded fuel but check before filling the tank. Whichever fuel you use, it is also more effective in the first 30 days. Be sure to use fresh fuel for the best result.
  • Blocked fuel lines. There is also the possibility that your fuel lines are blocked if dirt somehow entered your gas tank or you were using old fuel. To check if this is the problem, see if the inline filter is wet or dry. A dry filter shows that your fuel is not coming through. At the same time, you can check if your filter is blocked or causing a blockage.

Faulty Spark Plugs

Another reason why your riding lawn mower might not be starting is due to faulty spark plugs.

To check if your spark plugs are still in working order, you will have to remove them and inspect them to see any carbon buildup or cracks on other parts of the plug itself.

Oil Problems

If you do not check your oil level regularly, there is a chance that a low level of oil could be causing your lawn mower not to start.

Usually, this will happen with smart machines with safety features that don’t allow you to start unless you have enough oil.

Some systems protect your mower if there is too much oil, so be sure to check if that might be the issue.

Malfunctioning Or Flat Battery

If you are trying to start your riding lawnmower with a faulty or wrong battery, you will not be getting anywhere.

The easiest way to see if your battery is the problem is to listen to how your mower sounds when you try to start it.

If the engine clicks, does not crank, or cranks slowly, the chances are that you need to replace your battery.

Problems With Air Filter

Since engines work with flammable fuel and need air to operate, it is possible that your air filter is blocked and the cause of your mower not starting.

To check if your air filter is the problem, you can either take it out and try to start the mower without it or hold it up to the light to see if it is dirty.

Be sure not to operate the mower without an air filter.

Choke Problems

Like most modern cars, most recent riding lawn mower models have an automatic choke system.

However, if you own one of the older models or your mower is known to have a manual choke, you might be operating it in a way that does not allow your mower to start.

Problems With Ignition Switch

If your ignition switch or coil is faulty, you might also not be able to start your riding lawnmower. You will need an ohmmeter tool to check if this is your problem.

Once connected, you will see a connection between the b terminal and the s terminal. If there is no connection, it means that your Ignition switch might be the problem.

Operating Procedures

Riding lawn mowers come with many built-in safety features and operating procedures that you need to follow to start and use your mower correctly. If you do not follow the guidelines, many mowers will not start to prevent any harm. One of these features includes a sensor that ensures you sit on the seat properly.

Riding Lawn Mower Won’t Start – Fixing The Problem

Once you have found why your riding lawn mower is not starting, you will be able to solve most of the common issues relatively quickly.

The following are the ways to get your mower back up and running put into sections to simplify the process.

Fuel Problems

For the most part, fixing issues related to fuel is relatively straightforward.

If your mower does not have any gas in, it does not take a lot of effort to simply fill your tank again. Other problems might take longer, but the fixes are still easy to do yourself.

Wrong or Old Fuel.

If you have absentmindedly put the wrong fuel in your mower, the easiest way to fix the problem is to drain the fuel out of your tank.

If your mower was left standing with fuel for a while, it is also possible that the fuel has gotten too old to ignite correctly. You can also drain the old fuel from your machine.

Draining the fuel can be done by siphoning it using gravity or a particular pipe. If your fuel line runs across the bottom of your mower, you can also disconnect the pipe to let it drain out naturally.

Blocked fuel line.

If you have found that your fuel line is blocked, the easiest way to fix this problem is to disconnect sections of your line one by one.

If the piece of pipe you have detached is the problem, fuel will be unable to travel through it. You can either replace the part of the line or clean it by using a wire or a thin pipe brush.

Faulty Spark Plugs

lawnmower spark plug

You have found that your spark plug is causing your riding lawn mower not to start. You have two choices based on the exact problem.

If there is carbon buildup, you can clean the plug’s tip with a wire brush. However, if your spark plug has a crack, you will have to replace it with a new plug altogether.

Oil Problems

Like fuel problems, oil problems are also relatively easy to fix. If there isn’t enough oil in your riding lawn mower engine, you should fill it up to the instruction manual’s specifications.

If there is more oil in your mower than is needed, you will need to drain some of the oil out to ensure it is below the maximum recommended capacity.

Malfunctioning Or Flat Battery

For the most part, fixing your battery problems are straightforward. If there are wires that are not connected, you should connect them and attempt to start your mower again.

If it is still not starting and you have found the battery to be the problem, you should purchase and replace the battery.

Do not just throw the battery away, instead hand it over to professionals or people who can dispose of it properly.

Problems with Air Filter

If your air filter is clogged, you can simply take it out and wash it to clean it off. You can use a soft brush and water with soap to clean your filter and, after allowing it some time to dry.

Alternatively, you can purchase and replace the filter if your riding lawn mower’s air filter is beyond the cleaning point.

Choke Problems

If you are uncertain of how to use the choke on your riding lawn mower, you can usually find instructions in the manual. If you do not have a manual, the most common way to use a choke is to enable it fully when first starting your mower’s engine. Once the engine is idling, you can readjust the choke.

If there are other problems with your choke, I recommend that you get in touch with a professional to ask for help.

Problems With Ignition Switch

When repairing your ignition switch, you will want to look for loose or corroded wires. If there are old or loose wires, you should replace, reattach, or fix them if possible and if you are comfortable with that.

If there is still no connection when using the ohmmeter, you should look for the help of a professional.

Operating Procedures

When buying a sit-on lawnmower, there are usually instructions for use in a manual. Be sure to use the given guidelines in the manual to ensure your mower’s safe and continued use.

Some of the operating procedures that might cause your mower not to start are as follows:

  • The mower must be in neutral gear to start. Putting your mower in neutral might seem like a given, but there are plenty of times when an issue like this passes overlooked.
  • You must be seated correctly for the lawnmower to switch on. This feature ensures extra safety. Ensure that you are sitting as recommended to allow the engine to start.
  • There are safety switches on some models of sitting lawn mowers to prevent children or others from getting injured. If your mower model has a safety switch or trigger, be sure to use it correctly for your lawnmower to start.

Other Reasons Why Your Riding Lawn Mower Might Not Start

As with any other machine or vehicle, there are many aspects to consider when the engine isn’t starting or working as it should.

Other problems might prevent you from starting your mower, and most of these may require a professional to help you.

Faulty Charging System.

If you have had to replace or charge your mower’s battery frequently, there is a chance that your mower has a faulty charging system. The charging system is supposed to charge your battery while the lawnmower operates.

If this system is defective, you should see a professional to help you solve the problem and prevent further battery loss.

A Blown Fuse.

There is also the possibility that one of the lawn mower’s fuses has blown. If you are comfortable replacing it yourself, you should find the fuses close to the battery’s location.

If you have replaced the fuse, but it continues to cause problems, you should consult a professional to help you fix the issue.

Faulty Fuel Pump.

Another issue you might have to consider is that the fuel pump of your riding lawn mower is faulty or broken.

If you have found that this is the case, I recommend allowing a professional to replace it rather than doing it yourself.

However, if you have done such a task before, have the know-how, and have the right tools, you can do this yourself.


There are many reasons why your riding lawn mower might not be starting. Luckily, most common problems are easy to find and fix yourself.

However, if you are not comfortable fixing or working on your riding lawnmower yourself, it is recommended that you see a professional for help.

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