Isn’t it frustrating when you try to start your mower, and it refuses? It would be best to postpone your lawn care routine until you get it running. However, this is a challenging task, as there might be multiple reasons why a lawn mower won’t start.

You might think it’s all mechanical issues related to the mower engine. Yet there are electric and hydraulic components responsible for this complex issue.

If you are experiencing the same starting failure problem, keep reading this blog post. We’ll delve deep into the possible causes and remedies for this annoying problem. So, read on!

Why your Lawn Mower Won’t Start?

A lack of proper care and maintenance often leads to recurring starting difficulties or failure. And honestly,  regular changing of fluids and filters and constant inspection of internal parts seem like daunting tasks. However, these tedious precautions may spare you this major problem.

Now let’s dive deeper into the causes of the starting failure problem:

1. A Clogged Air Filter 

The air filter protects the engine and carburetor from debris and dust. Grass clippings will easily reach the engine without this component due to constant airflow.

Eventually, these fine or heavy particles will damage the engine, leaving a malfunctioning, dirty carburetor behind. You’ve probably guessed that the cost of repairing such damages is expensive.

That said, a clogged air filter will lose its efficiency at blocking dirt particles and debris. Also, dirty air filters will prevent necessary airflow from reaching the engine. So, the vital component of the combustion process will be missing. Subsequently, the engine won’t be able to start at all.

2. Check the Condition of the Plug Wires

As with any electrical wire, the wires of a spark plug can become loose or torn. These wires transmit current from the ignition coil to the plug by default. Bad wires will interrupt the transmission of electrical current. Therefore, the ignition of the air and fuel mixture won’t happen.

3. Inspect the Plug 

Have you checked and fixed the issues with the air filter, and nothing has changed yet? Then it is time to look at the spark plug. This component is essential for igniting the fuel and air mixture inside the engine. A spark plug is small in size, but it generates the necessary spark required for starting the motor.

Spark plugs are light gray by default, but this color might change when they go bad. A bad spark plug usually turns black. This color change results from carbon deposits on the insulator tip.

4. Check the Fuel cap 

Checking the cap is helpful for both starting failure and power loss issues. A fuel cap vent is standard in various lawn mower models. This small component allows the hot fuel to vent and cool down.

A vented cap prevents the formation of a gassy vacuum inside the tank. If this vent malfunctions, the vacuum volume will significantly increase. Eventually, the fumes will restrict the flow of gas. This makes the mower unable to start or suddenly lose power.

5. Take a Look at the Deck

The mower deck prevents the cut grass and sharp blades from reaching the rider or the motor. Aside from securing the engine from dirt and clippings, the mowing deck is also designed to protect the blades from clipped grass.

While efficiently performing its function, there is nothing to protect the deck from grass and debris. So the deck gets more frequently clogged with cut grass. This makes the blades unable to rotate and cut. A jammed lawn mower deck usually results from cutting wet grass.

A clogged deck will not only prevent the mower blades from cutting, but it will also prevent the engine from running. The clogging in the deck will make the starter rope jammed and impossible to start. Subsequently, the engine of your lawn mower won’t start.

6. Check the Safety Bar

As with any outdoor power equipment, such as chainsaws, an emergency safety feature stops the machine immediately; in saws, this feature is known as the chain brake, but in mowers, it is known as the safety bar. When this bar is squeezed, the engine should run. And the engine stops when you disengage or release the bar.

This bar will prevent the engine from starting if it remains in the release position.

7. Inspect the Fuel Level

Let’s admit it, fuel levels are always taken for granted. You might be trying very hard to start the engine and looking for complex reasons for this issue. However, you may never consider checking the gas levels inside the tank. 

The tank could be running out of gasoline. Moreover, the tank could be filled with dense or dirty fuel. All these possible scenarios can make the mower’s engine unable to start.

8. Take a Look at the Flywheel

In a lawn mower’s engine, a flywheel keeps the motor spinning. Moreover, it stores excess energy to keep the engine running. This component contains a brake that controls the rotational motion of the cutting blades and the engine.

If the flywheel brake is engaged, the engine will stop. It will not run in the first place if the flywheel key is pulled.

9. Check the Battery

A battery is not only a mainstay in battery-powered lawn mowers. It is essential for running petrol mowers too. The source of electrical current is required for starting the engine. A mower’s battery can stop working for different reasons. It might die or suffer from improper cleanliness.

10. See the Fuel Filter 

A fuel filter prevents debris from reaching the carburetor. So, simply put, it purifies the flowing gas from any contaminant particles. Fuel won’t pass through and get to the engine when this component is excessively clogged. 

How to Fix a Lawnmower That Won’t Start?

The numerous causes of starting failure in a lawnmower can be fixed in many easy ways. Usually, these simple solutions work for different types of gas-powered mowers. However, if none of these workout, you should seek expert advice.

1. Change the Air Filter 

You should always clean your filter to keep the engine and carburetor free of debris. Most lawnmower manufacturers recommend cleaning paper filters every 25 hours of running. If cleaning fails to free the filter from clogging, you must replace it. You should replace this paper component every 90 days.

As every model of mower has its design, you might be confused about replacing the component for the first time. But generally, you should shut off the engine and remove the spark plug.

2. Troubleshoot Loose Wires 

You can always tell there is a problem with the spark plug wires with your eyes. Their appearance reveals their condition. They are not the issue if they look correctly connected to the plug. You will need replacement wires if they appear torn, loose, or with broken terminals.

3. Clean the Spark Plug 

If you suspect a problem with the spark plug, you should first do some cleaning. You will suspect a problem with this plug when you spot it covered in soot. Also, the engine of your lawn mower won’t start. So, a black spark plug needs proper cleaning.

To correctly clean it, you must remove the plug from the cylinder. It would help if you started by disconnecting the spark plug wire. Then, it would be best to use a scrench to unscrew the plug from the machine.

To easily remove stubborn buildup, apply some carburetor cleaner to the plug before soaking it in water and gasoline for a few minutes. All this can loosen tough debris. Finally, try to scrape the stains with a knife or use a wire brush to ensure ultimate cleanliness.

Before returning the plug to its original location, ensure it is completely dry. If this does not work out, you should get a replacement. These spare parts are cheap and easy to find online and in land-based hardware stores.

4. Replace the Cap

The gas tank cap is the main culprit in different lawn mower engine issues. It contributes to difficulty starting, starting, and dying, and even fuel tank leaks. However, it is often disregarded when one of these issues occurs. In the case of starting difficulty, the cap might be faulty, more specifically, its vent.

In this case, there are no possible repairs other than getting a new cap. Remember that these caps are not completely universal, but some can be used interchangeably, provided they have the correct fitting.

5. Ensure the Deck’s Cleanliness

A clean deck contributes to smooth and problem-free engine starting. After each mowing session, you should clean the deck. Luckily, this part is easy to clean. All you should do is roll the machine on one of its sides. This allows you to see the deck more clearly. Bring a small trowel along to remove stuck debris easily.

6. Squeeze the Safety Bar

The emergency safety bar is often overlooked when a lawn mower engine fails to start. So, you must ensure that the bar is squeezed and disengaged. If nothing is wrong with the engine, this action should get it to start smoothly.

7. Refill the Tank

If you find insufficient gasoline in the tank, refill it with the appropriate type. Also, if the condition of the gasoline is not as it should be, it must be replaced. You should drain the tank completely and refill it with fresh liquid per the manufacturer’s recommendations.

To correctly clean the tank, you should use a syphon pump. Adding a fuel stabilizer is a recommended step to prevent gasoline evaporation.

8. Disengage the Flywheel

An engaged flywheel won’t let the engine run. This component in the engaged position will not allow you to pull the cord. So, make sure to readjust its position to deactivate the brake.

9. Replace the Battery

Replacing is the ideal solution for a dead battery. However, it would be best if you fully charge it first. Also, cleaning corroded battery terminals might be a good solution. You can also tighten the loose battery cables if you find them.

10. Clean the Fuel Filter

A clogged filter should be cleaned first. If cleaning does not work, you should throw it away and get a new one.

5/5 - (6 votes)