Riding Mower Turns Over But Won’t Start: 6 Ways to Fix

My lawnmower isn’t that old, so you might be wondering why it keeps trying to turn over but won’t actually start.

If your riding mower turns over but won’t start, it could be due to a variety of reasons including old fuel or problems with fuel supply, clogged carburetors, and even spark plug problems, which could be to blame.

This article will discuss some of the most common reasons a riding lawn mower turns over but doesn’t start and suggest troubleshooting procedures.

Riding Lawn Mower Turns Over but Won’t Start

What Causes Riding Mower Turns Over but Won’t Start?

When the engine of your lawn mower turns over easily but won’t start, you will need to figure out what’s wrong. So, riding lawn mower engines work because of three important parts: the air intake, the spark, and the gas. If any of these things are broken or missing, the engine probably won’t start.

1. Old Gas

Old gas can be a common cause for a riding mower not starting. Over time, the gasoline loses its effectiveness, and the fuel can become stale and clog the carburetor or fuel lines.

Gasoline can go bad after about 30 days and become contaminated with water or other contaminants that can cause the mower not to start.

Occasionally, the fuel bowl can become clogged with old gas, preventing fuel from entering the piston.


You’ll need to get a fresh supply of gas. Don’t mix the bad gas with the good gas. First, use a siphon to get rid of the old gas. Then, put the new gas in.

2. Bad Spark Plug

If the spark plug isn’t working properly, there won’t be a spark to ignite the fuel in the engine, and the mower won’t start. If your mower isn’t receiving a spark strong enough it is tough to start the engine.

It’s possible that the spark plug is broken, corroded, or clogged. When a mower’s plug wire comes unplugged, it’s not uncommon for the mower to stop working.

You may possibly be unable to get your mower started because the spark plug wire isn’t making a solid connection with the spark plug’s terminal.

Spark Plug
Spark Plug


The spark plugs should be inspected. To do this, the spark plug boot should be removed and the spark plug should be unscrewed and inspected for signs of wear or damage.

If you find a bad spark plug, clean or replace it. Check the electrode, ceramic coating, and wire terminal to determine which mowing option is best.

Your problem may be caused by a damaged coating or a burnt, shortened, or absent electrode. Replace the spark plug.

If the spark plug tip is dusty, you can clean it with a little brush and a light solvent to restore spark and wire connection.

Your problem may potentially be caused by the spark plug wire not making touch with the starting mechanism.

  • Pushing the rubber wrap down around the plug may tighten it.
  • The wire should be visible and exposed enough to establish contact inside the shroud.
  • If the rubber shroud is ripped or worn, replace the spark plug wire or shroud.

3. Dirty Air Filter

The air filter is responsible for preventing dirt and debris from entering the engine; however, if the air filter becomes clogged, it can limit the flow of air and make it impossible for the engine to start.

If the filter is covered in dirt, grass, or some other contaminant, this may be the reason for your lawn mower turning over but not starting.

Air Filter
Air Filter


The combustion process requires enough air. Clean and inspect your air filter every 25 hours.

If your air filter is covered in sand, dirt, grass, leaves, or anything else, blow it out to get it running again. Tap the air filter upside-down to remove big debris.

Blow out with an air compressor. This will release many filter-trapped tiny particles. If neither technique works, replace the air filter.

4. Safety Switch Issues

Mower won’t even start if safety switch isn’t engaged, like the seat or emergency brake. However, there is a remote possibility that a switch is functioning intermittently because it is dusty or the contacts are not making good contact.

Your riding mower might try to turn over, but not actually start, if this happens.


Shifting your weight to different areas of the seat and trying to start the mower will help you determine whether or not the switch is functioning properly.

It’s possible that the switch under the seat is broken if nothing else seems to be wrong.

As a second step, make sure the emergency brake switch is making contact; if it isn’t, the mower won’t start even when the brake is applied.

5. Clogged Carburetor

A lawnmower’s engine may turn over but it will not start if the carburetor is dirty or blocked with debris. In order for the engine to function correctly, it is the job of the carburetor to combine the air and fuel in the appropriate proportions.

It is possible for the carburetor to become clogged, which will impede the flow of fuel and make it impossible to start the engine.


Clean the carburetor to fix this. Find your mower’s carburetor near the air filter. Disconnect the carburetor’s hoses and wiring. Remove the mower carburetor.

After removing the carburetor, clean it. Spray the carburetor with cleaner. This loosens dirt and detritus. After that, scrub obstinate particles with a little brush. Vacuum any leftover dirt and debris,

Reassemble and run the mower after cleaning the carburetor. Replace the carburetor if it won’t start.

6. Fuel System Not Working

The gasoline system may have a few culprits. The carburetor may get gummed up if gas has been left in the mower for a long time.

If the gasoline filter is full of debris or the clear container around it is completely dirty, this may be the problem.

You must exclude the other two variables to test the fuel system. If the air filter is clean and the spark plug is intact, spray starting fluid directly into the chamber. If the mower starts this way or begins and stalls, it’s a fuel supply issue.


If you find that your gasoline filter is really clogged, you may be able to change it without assistance.

To replace the fuel filter, just disconnect it from both ends and reconnect it in the same manner. In order to contain any fuel that may leak from the lines as you disconnect them, use a bucket.

You can either clean the gummy carburetor or replace it if you think this is the case.

If your mower has a fueling system problem, check the choke system too. The choke restricts carburetor airflow to improve fuel mixing. Before starting, switch your choke lever to full choke.

Related Post: Riding Lawn Mower Stopped Running While Mowing: (Reasons & Fixes)

Frequently Asked Questions (FAQs)

Will low oil cause lawn mower not to start?

The answer is yes- low oil level can sometimes make a lawn mower fail to start.

What is gas shot test?

The gas shot test is a good place to start as fueling difficulties cause most riding mower starting problems. 
Start this test with fresh gas and no air filter. Spray starting fluid or gas into the carburetor. Start your mower normally. A fueling issue caused your mower to start. If your mower didn’t try to start, it’s likely a spark issue.

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