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Tips For Troubleshooting a Malfunctioning Lawnmower Engine

We don’t think about it much, but our lawn mower is a complicated device.  Luckily, most of the time we don’t need to understand what’s going on “under the hood:.  Rather, we take it out of the garage, start it up, and get our work done.

That’s not always the case though. 

Sometimes, you pull the starter cord and you hear nothing. No signs of life. This could be caused by various issues, which we’ll discuss below and the steps to be followed to fix them.

Safety Precautions

Before you dive into the steps of finding a solution as to why your lawnmower isn’t operating, there are some safety hazards to take into consideration.


As you’ll be interacting with various substances (such as gasoline and engine oil)  and generally, using your hands a lot while fixing your mower, protecting them is a good idea. Types of gloves include latex, vinyl, and nitrile rubber. Choosing the right glove is essential as some have high resistance to gasoline/oil while others don’t.

Read the Manual

It’s highly recommended that you read the lawnmower or the engine’s manual before fixing/removing any parts to prevent injury and damage to your equipment.

Remove Flammable Items

Gasoline/petrol are flammable substances so make sure you eliminate all items that can ignite. Having proper ventilation also helps get rid of the vapor that builds up.

Disconnect the Spark Plugs

A spark plug is the part in the lawnmower that creates a spark to ignite the mixture of air and fuel that was delivered to the cylinder by the carburetor. Disconnecting it is very important, alongside waiting for a hot engine to cool (if you’d been previously using it) to prevent accidental spinning of the blade while it’s being cleaned.

Empty the Gas Tank

This will prevent the fuel from dripping out if the fuel level is too high when the mower is flipped on its side. The extra gas can be collected using a siphon pump in an appropriate container. If the gas level is low, disregard this precaution.

Problems and Solutions

Now that you’ve gone through all the safety precautions required, it’s time to find out why your lawnmower might not be starting and how to fix it.

Starting the Mower

A common cause why your lawnmower isn’t starting is that you may not be starting it the right way. People believe that as soon as they take their mowers out of storage, and pull the starter cord, the mower will be up and running. However, there’s a right way to ensure the proper start of your mower.

  1. Load the gas tank with the help of a funnel
  2. Run an oil level check
  3. Add new fuel to the mower
  4. Make sure the choke (the device that concentrates the vapor pulled into the engine to aid starting) mechanism works
  5. Press the primer (the pump that absorbs the fuel from the tank into the carburetor) button 5 times
  6. Pull the starter cord until the engine starts
  7. Once the engine starts, turn off choke mechanism (if not automated)

Water in the Tank

This could be due to exposure to moisture during storage or from faulty fuel that was mixed with water. To fix this issue, use a torch to see the droplets of water at the bottom of the tank and soak them up using a sponge or a small piece of cloth tied to a long screwdriver.

Clogged Air Filter

The primary function that the air filter serves is removing dirt and grime from the stream of air entering the engine to avoid clogging and overconsumption of fuel. This requires that you continuously clean the filter or annually replace it.

Smoking Engine

If the smoke coming out of the lawnmower is black, this may be due to the oil chamber being too full or having a leak if tilted. Check for this issue once the engine cools. However, if the smoke is white, this may indicate a more serious problem that requires inspection by a professional.

Engine Slows Down

This may be due to damage or dislocation in the drive belt. If you find that it’s loose, reattach it and if it’s damaged, replace it. If the engine is powered by batteries, check the battery to make sure it’s not malfunctioning.

Carburetor Maintenance

The carburetor (carb) should be removed and checked for any signs of clogging within its holes. If clogged, these holes can be cleaned using a wire brush. Soaking the carb in lemon water then brushing it will accelerate the process. Also, check all parts of the carb to ensure their proper functioning or if they need to be replaced.

Lawnmower Hibernation

When it’s time for your lawnmower to go back into the storage, it’s highly recommended to follow a few steps for smooth running next time you decide to use it.

  1. Clear the fuel in the engine by running it till it cuts out.
  2. Put a few drops of oil into the spark plug hole to prevent corrosion.
  3. Remove grass clippings from the blades as these can become acidic over time and erode the metal.
  4. Place the mower in a dry, covered space.

Healthy Lawnmower, Healthy Garden

Taking good care of your lawnmower and knowing how to fix it, ensures that it lasts a long time and reduces the expense of hiring a professional. Now whenever your engine starts sputtering, you’ll know what to do.

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