4 Signs That Your Lawn Mower Engine Is Blown (+Fix)

We all need a lawn mower machine to maintain a well-decorated garden. However, using the lawn mower for more than a year can cause some problems with the engine. If you notice smoke releasing from the engine or a burning smell of the fuel, the lawn mower engine is blown.

If your lawn mower engine is blown, you will notice the following signs:

  • The tailpipe will release a whitish/bluish smoke.
  • Oil leakages in the engine.
  • Lack of sufficient power and pressure in the lawn mower.
  • Poor compression assessment.

Understanding why a lawn mower engine blows is essential to fix the machine and prevent this problem in the future. This article will discuss each of the signs and causes in detail. So, read carefully.

Lawn mower engine repair 3

What is meant by a mower head gasket?

Many people may not know how a combustion engine works and haven’t heard the word gasket.

The head gasket is a seal that is made of layered metals.

It is compressed between the engine head and the block. 

The gasket will prevent fluid leakages and ensure no pressure is coming out from the engine compartment. 

Various factors, like poor quality fuel, damaged spark plug, greasy air filters, etc., can cause a blown gasket head. 

Any of these factors will cause high pressure in the cylinders and serious harm to the head gasket.

What are the effects of a blown lawn mower engine?

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A blown lawn mower engine will cause various problems to the machine, like pressure leakages, oil seepages, ignition issues, etc.

If the blown engine is not replaced timely, then the running cost of the lawn mower will increase. 

The expense will be further increased by adding the cost of the burned oil. 

When the engine blows, the piston head and the spark plug get damaged, and the engine becomes unsteady and requires a complete replacement.

What are the signs of a blown lawn mower engine?

Lawn mower repair 3

The lawn mower’s engine gives power to the blade, which enables the cutter to trim the grasses effectively.

The engine draws air and fuel as it moves and spin.

The spark plug ignites the mixture of air and fuel, producing electrical currents from the flywheels.

If, for some reason, the engine blows, the ignition will not occur.

As a result, the mower will not get the power to run and will stop working.

If the engine of your lawn mower is blown, you will notice the following signs:

1. Smoke from the tailpipe

Smoke is one of the most common signs indicating a problem with the combustion system.

The tapeline of the lawn mower starts releasing white or bluish smoke when the engine blows out.

The smoke is a sign of partial combustion that the fuel has yet to burn completely.

2. Oil leakages 

There will be oil leakages if the lawn mower engine blows.

The head gasket isolates the space between the engine and the cylinder, restricting the creation of a vacuum required for ignition. 

If the gasket leaks, there will be a line of oil where two components are held together.

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3. Poor compression assessment

There will be low compression if the engine blows.

Compression is the term used for the pressure in the piston chamber where the fuel and air get mixed. 

Due to this pressure, the piston chamber moves outwards, spinning the crankshaft. 

The cylinder will be filled with air spaces if the engine blows, leading to poor compression.

4. Loss of power and pressure from the lawn mower

If the engine blows, the lawn mower will be left with less power and pressure.

If the lawn mower is not starting and there are oil leakages, the gaskets are blown. 

It indicates that the mower has lost the power to carry on with the combustion.

What cause a lawn mower engine to blow?

Lawn mower engine repair 4

It is important to ensure that the engine always functions well.

The awareness regarding the failure of the engine will help you prevent any such problem in the future. 

1. Greasy air filters

The air filters keep the lawn mower clean by not allowing dirt and debris to enter the engines.

However, if the air filter becomes dirty, the dirt will enter the engine and cause various problems reducing the machine’s lifespan. 

The dirt and debris will restrict the fuel and air from reaching the engine. 

As a result, the lawnmower engine blows due to insufficient oxygen for ignition.

2. Low or greasy oil levels

The oil travels to the lawn mower’s parts, lubricating them and reducing friction.

If the lawn mower is left with less oil, the components will not remain lubricated, due to which the engine will start heating. 

As a result, the pistons will fuse, and the engine will seize. You might hear knocking sounds from the engine. 

But if the oil is greasy and dirty, it will lose all detergents and cooling particles, causing huge destruction to the engine.

3. Damaged spark plug

Lawn mower spark plug fix

In a lawn mower, the spark plug can ignite the fuel in an engine.

However, if the spark plug has any problem, the engine will stop working, and the ignition will not occur.  

Any damage to the spark plug will lead to huge engine gas consumption, causing it to blow.

4. Using a poor-quality fuel

The gasoline used for producing power in the lawn mower usually starts deteriorating within 1 to 2 months from when you pumped it into the gas station.

The gasoline has ethanol that pulls moisture, hence making it watery. 

Similarly, using old oil will prevent the engine from starting and running smoothly. 

Also, the fuel’s moisture content will cause engine corrosion.

Hence, the fuel can damage the lawn mower completely.

5. Incorrect blade position

The blade in the lawn mower is used for trimming the garden grass.

The lawn mower will start shaking if the blade starts to bent or lose. 

If you don’t address this problem within time, the shaking will ultimately damage the crankshaft, causing the engine to blow up.

Remember, any disruption in the blade will not help you to maintain a beautiful lawn.

Also read: Is It Better To Sharpen Or Replace Mower Blade?

How to maintain a lawn mower at its best?

Regular checks and maintenance will keep your lawn mower in the best condition and will help in its effective operations.

Besides, the lawn mower’s maintenance cost is very low compared to the repair cost after its damage. 

Following the above points will help you to maintain your lawn mower in good working condition. 

Furthermore, it will enable you to find and solve minor issues until they become major ones.

1. Replace the oil

The engine oil is required to smooth all the moving parts.

The oil is also a cooling agent for the engine’s internal components. 

Therefore, oil replacement is important to run the machine effectively.

Experts recommend changing the oil every 25-50 hours, depending on the engine’s performance and how frequently you have used the lawn mower. 

Ensure you always add oil correctly to keep your lawn mower in the best condition. 

The engine will suffer from severe damage if it has low oil levels. 

Also, if you add the oil in excess amount, the lawn mower will start releasing smoke as it burns the extra oil.

2. Change the spark plug

Lawn mower spark plug

The spark plug has electrodes that should be kept sharp and clean to produce the spark for combustion.

As you use the lawnmower, the spark plug will start to wear and tear. 

Therefore, changing the spark plug once every year or as your manufacturer directs to run the engine is essential.

3. Change the air filters

Experts advise cleaning the foam air filters every 25-50 hours after you have used the lawn mower.

However, if you use paper air filters, you can replace them once every mowing season or after 300 hours of using the lawn mower. 

But, if your lawn is dusty, you will need to frequently clean or change the air filters. 

Check your foam air filters regularly for any sign of yellow stains or breakdowns, as these indicate that it’s the correct time for their replacement. 

Make sure the new air filter will be suitable for your lawn mower.

4. Periodically sharpen the blades

Lawn mower fixing blade

Blunt blades can cause the motor of the lawn mower to overwork.

Looking at their tips, you can easily identify whether the blades are shark or blunt. 

If the blade is blunt, you will notice the ends are brown and rugged. 

Before sharpening the blade, check whether it is warped, chipped, or bent. 

If the blade has no problem, sharpen it to keep it in good condition.

But, if you find any defect in the blade, replace it with a new one. 

However, the blades need a repair service if you notice any vibrations while operating the lawn mower.

Also read: 9 Ways To Sharpen A Lawnmower Blade Without Removing It (+Mistakes To Avoid)

5. Clean the deck

Keep a check on the deck for any grass clippings.

The grass clipping can accumulate in the mower deck and cause rusting. 

If you like washing the deck after mowing, dry it after rinsing. 

You can use a blower to remove the grass clippings in inaccessible areas.

6. Replace the fuel

Lawn mower gas refill

It is advisable to replace the fuel after every few months.

If you don’t change the fuel and let the old gas sit in the engine, the old gas will degrade in the carbonator and clog it. 

The old fuel, which isn’t replaced for months, will damage the seals and fuel lines.

You can drain the old fuel from the lawn mower during the mowing season, as it will not cause any damage to the machine.

Also read: Will Mixed Gas Hurt A Lawn Mower? (5 Mistakes People Make)

7. Use a fuel stabilizer

Fuel stabilizers can be used to slow down the process of gasoline oxidation.

If you rarely use a lawn mower, you can add a fuel stabilizer to prevent it from breaking down. 

Consider adding a fuel stabilizer to a new gasoline instead of the old gasoline that stayed in the lawn mower for more than a month. 

If your lawn mower has old gasoline at the end of the mowing season, remove it, fill it with new gasoline, and add a fuel stabilizer.

Final words

A well-functioning lawnmower will help you to maintain a well-manicured lawn. Knowing the reasons that caused the engine to blow will enable you to stop possible damages through proper maintenance.

Furthermore, you can also detect other issues with the lawn mower, if any. It is recommended to allow the lawn mower to rest for a few hours after use. Also, ensure the lawn mower is kept in a cool place.

After the mowing season, drain the old fuel to prevent the engine from rusting. Keep an eye on the symptom of head gasket problems to save your time and money.

Reference: Lawn Mower Technology, Lawn Mower SafetyLawn MowingLawn CareMowing your lawn.


Hello everyone, My name is Richa and I am here to make you a better gardener by creating an in-depth and helpful resource for all the fellow gardeners out there. If I could help even a few people understand their plants better then I call it a success for my efforts.

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