Why Lawn Mowers Will Not Turn Over – Solved

Is your riding lawn mower having trouble turning over? This can happen if it has not been used for a long time. If you just took the mower out of winter storage and it will not run, you are not alone. I have seen this before, and in this guide I walk you through the solutions and how to prevent it.

If your riding mower refuses to turn over, old fuel is probably clogging the engine. If fuel is not the problem, clean or replace the spark plug. A dirty air filter can also cause the engine to stall.

Old Fuel

Lawn mower fuel should be replaced every 30 days. If you just let it sit there, the gas turns gummy and clogs the carburetor. Imagine if you left fuel in the tank for 2-3 months during winter.

Before going over the solution, I want to tell you there are two ways to prevent this from happening in the first place.

• Empty the fuel tank if you are going to store the mower for winter. Quick and easy.
• If you want to keep fuel in the tank, add Sta-bil Fuel Stabilizer. This will prevent the fuel from gumming up.

Now let us look at the solution if old fuel was left in the tank.

Solution

1. Open the fuel tank and drain of the gas as much as you can.
2. Put a hose or pressure washer in the tank and spray hot water. If you don’t have a hose or pressure washer, just pour hot water.
3. Put Star Brite or a cleaning detergent in the tank.
4. Use a small brush to remove debris on the tank walls.
5. Pour the liquid out into a pan. Dispose properly.
6. Dry the tank completely.
7. Pour fresh fuel.
8. Turn on the engine. Do not be surprised if it smells gassy thanks to the new fuel. That is normal.

Leaking Reservoir

A physically damaged tank can leak fuel. This could explain why your riding mower will not turn over, as there is not enough fuel left.

A small leak can be difficult to spot. At first you notice oil around the tank, then it spreads to other parts of the mower. If you notice that your mower runs out of fuel faster than usual, fuel might be leaking out.

Solution

Check the fuel tank for holes or tears. You have to either repair the tank or get a new one. If the leak is small, you can get it fixed. If the tear is a large one and the tank is old, better get a replacement.

Always check the reservoir when you replace the fuel. A small crack can spread if not repaired right away. Old fuel tanks are the most vulnerable so regular maintenance is a must.

Dead Battery

A riding mower with a dead battery is not going to run. Even if you fill the fuel tank, it still needs a battery to get the engine running.

Solution

The first step is to check the battery. Wipe it clean and use a battery tester to check if it is still working. If nothing happens, look for loose wires or signs of physical damage.

If the battery won’t carry a charge, it is probably dead. Use another charger if possible. If the battery still won’t respond, you need to replace it.

I want to point out that riding mower batteries last 3-5 years. But I have seen well-maintained batteries last 8 years. If the battery is misused, it can die in a year or less. So a lot depends on how well you manage it.

You should replace the battery if it is no longer working. Buy only the type that the manufacturer recommends to prevent complications.

Spark Plug Needs Replacement

A dirty or damaged spark plug is always going to cause an engine problem. This is true for cars and lawn mowers as well. Fortunately it is easy to fix this problem.

Solution

Disconnect the spark plug. Use a wire brush to remove the soot.

After cleaning, look for cracks or signs of burnout. Replace if damaged. If the spark plug looks fine, put it back and try the mower again.

If the mower still won’t turn over, try a spark plug tester.

You can also use the tester on lead that links the spark plug to the lawn mower. Take the spark plug out and set the tester on the lead. Position the other end of the tester on a working spark plug. See if it ignites the engine.

If the spark plug old, it might be worn out already. Riding mower spark plugs should be replaced once a year or after 30 hours of engine use. You should only use the spark plug recommended by the manufacturer to avoid problems.

Whether it is dirty or defective, spark plugs need to be in working condition. If there is an issue with it, even the pull cord will not work.

Related. Why Lawn Mower Pull Cords are Hard to Pull

Fuel Does Not Flow

Sometimes the problem is fuel does not make it to the engine. There are many reasons why this can happen. But based on my experience it is usually due to a clogged carburetor.

Solution

Make sure the choke plate moves smoothly. You can find this atop the carburetor throat. If it is not functioning properly, it needs cleaning. Spray some carburetor cleaner and try the mower again. If it still won’t work, the valve might be clogged.

If the entire carburetor is dirty, it is probably soot or oil sludge. Clean the carburetor and check for signs of damage too.

If there is a lot of oil residue, you might have to disassemble the carburetor. You should get a carburetor rebuild kit so you can replace any worn out parts. But if the carburetor is heavily damaged, it is better to buy a new carburetor.

Defective Fuel Filter

The fuel filter removes impurities in the fuel before it gets to the engine. If the filter is dirty, debris will reach the engine. Not only will it stop a lawn mower from starting, but debris can cause permanent damage.

Solution

A clogged fuel filter has to be replaced. It is good practice to replace the fuel filter at least once a year to prevent degradation.

The once a year frequency is the minimum. Replace the filter sooner if it no longer works or gets clogged. If the fuel in the tank looks dirty, the filter needs to be replaced.

You can find the fuel filter location in the manual. How you replace the filter varies from mower to mower. With some you have to empty the fuel tank first. With others you might need to clamp the fuel line.

When you see the filter, take it out. If it is more than a year old, install a new filter. If the filter is still new and has no damage, you might be able to clean and reuse it. Personally I prefer to just use a new fuel filter.

Blocked Air Filter

The air filter collects the dirt and prevents it from reaching the engine. Too much dirt and the filter gets clogged and prevents the lawn mower from turning over. This requires cleaning or replacement depending on the situation.

Solution

Riding mower air filters are usually near the engine. Lift the filter housing and take the filter out. Wipe the filter seating.

There are two types of air filters: foam and paper. A dirty paper filter is just that, covered with dirt. It has to be replaced.

Foam filters are reusable. Clean it under running water, dry and put it back on the filter seat. However you should replace the filter if it is damaged.

While foam air filters are washable, you should replace it every three months. If the filter gets too dirty, replace it sooner.