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How To Tell If Lawn Mower Engine Is Blown

A lawnmower is essential if you intend to maintain a well-manicured lawn. However, many things can go wrong while using the machine, rendering the lawnmower inefficient. You may be wondering how you can tell if its engine is blown. We talked to the experts, and this is what we gathered.

If the engine of your lawnmower blows, you will notice either of the following signs:

  • White or bluish exhaust smoke billowing from the tailpipe.
  • Oil leak.
  • Failed compression assessment.
  • Insufficient power and pressure.

You now know how to identify a blown lawnmower engine. Nevertheless, it's essential to understand why the engine blows and how you can avoid this. Dive in as we will address each of these issues here.

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Lawn mowers cut grass. Garden work concept background, How To Tell If Lawn Mower Engine Is Blown

How to identify a blown lawnmower engine

Professional serviceman is repairing a lawnmower, unscrewing a spark plug. Man repairing a mower in a workshop

A lawnmower engine powers the blade, enabling the cutter to trim grass at a consistent height. As the engine spins, it draws in air and fuel. The mixture is then ignited by a spark plug which generates electricity from a flywheel that rotates with the engine. When the engine blows, combustion won't take place. Consequently, mechanical energy to power the mower will not be released.

To determine if the engine or the head gasket is blown, check for the following:

  • A cloud of white or bluish exhaust smoke spews from the tailpipe. Smoke indicates incomplete combustion since the fuel is not burned completely.
  • Inspect for an oil leak on the lawnmower. The head gasket isolates the space between the engine and the cylinder block to create a vacuum necessary to maintain combustion. If the head gasket blows, the oil will leak.
  • Conduct a compression assessment. Compression is the pressure in the piston chamber when air and fuel are squeezed. This pressure then moves the piston outwards and rotates the crankshaft. If the head gasket blows, there will be air spaces in the cylinder, resulting in low compression.
  • Observe if the lawnmower has enough power and pressure. If the engine is blown, there will be inadequate power and pressure.

Why does the lawnmower engine fail?

Mower components or lawn mower

The engine can easily pass for the most critical component in a lawnmower. Therefore, you should take care to ensure that it functions correctly. Understanding why the engine fails will help you avoid this pitfall.

Dirty air filter

The air filter prevents dirt and debris from entering the engine via the carburetor. When it is dirty or worn out, dirt will make its way to the engine causing potential start-up problems and reducing its lifespan. Dirt also prevents oxygen and fuel from reaching the engine. In the absence of enough oxygen for combustion, your lawnmower's engine sputters.

Low or dirty oil

Oil travels throughout the moving parts of your lawnmower, lubricating them and minimizing friction. When your lawnmower has no oil or the oil level is low, the engine components will not be lubricated, thus causing overheating. Additionally, you will hear knocking sounds in the engine. The pistons will fuse and seize the engine.

If the oil is dirty, it degenerates and loses its cooling agents and detergents, causing considerable damage to your engine.

Worn spark plug

The spark plug is tasked with igniting the fuel in your engine. If the spark plug fails, your engine will not start since combustion will not occur.

A damaged spark plug may also cause excessive gas consumption. Moreover, you may need to tug extra hard for longer than usual on the rewind. You may also notice that the lawnmower loses power as it moves.

Using old fuel

The gasoline used to power your lawnmower starts to degenerate within 30 to 60 days from the time it is pumped at your local gas station. It contains ethanol that draws moisture from the air, thus watering down the gasoline.

Old fuel can cause your lawnmower's engine not to start, hinder it from running smoothly, or even cause the machine to die during mowing. Furthermore, moisture absorbed can cause corrosion of the lawnmower's engine.

Wrongly positioned blade

The blade is responsible for cutting the grass. It sits within a deck that keeps grass and other objects from haphazardly flying when struck. The mower will shake if the blade is bent, loose, or sharpened unevenly. If the issue is not addressed, the shaking will eventually impair the lawnmower's crankshaft, causing possible engine failure.

Granted, if the blade is imbalanced, you will not maintain a well-manicured lawn.

Best practices for lawnmower maintenance 

Turning on the lawn mower by gardener

Regular maintenance ensures that your lawnmower is in peak condition and operates efficiently. Moreover, the cost of maintaining your lawnmower is minimal compared to repair costs incurred after a significant break-down. Performing these exercises often will keep your mower in good working condition longer. Additionally, it will enable you to detect and resolve minor problems before they metamorphize into significant issues.

Change the oil

Engine oil creates a buffer between the moving parts. It also acts as a cooling agent of the engine's internal components and keeps carbon and used oil from blocking oil passages in the engine. Changing the oil ensures that it has the right proportions to perform the expected duties.

It is advisable to change the oil after every 25-50 hours of use, depending on the engine's capacity and how often you use the lawnmower.

Ensure that you add the correct oil quantity to keep your mower in good condition. While low oil levels can cause irreversible damage to the engine, if you add more oil than the required quantity, your lawnmower will emit smoke as it burns the excess oil.

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Replace the spark plug

The electrodes on a spark plug should be kept clean and sharp to produce the required spark for ignition. However, the spark plug is subjected to wear and tear as you operate your lawnmower. It is advisable to replace the spark plug annually or as the manufacturer directs to keep the engine running.

Replace the air filter

It is recommended to clean the foam air filter after every 25 hours of using your lawnmower. Further, replacing the paper air filter once per mowing season or after 300 hours of operating the lawnmower is advisable. However, you may need to clean or replace the air filter more often if subjected to dusty conditions.

Regularly inspect the foam air filter for any signs of break-down or yellow staining as these may be telling indications that it is time to replace it. Check with the manufacturer's manual to find out the recommended type of air filter. Ensure that the replacement filter is suitable for your lawnmower.

Sharpen the blade

Lawn mower blade sharpening.

Dull blades cause the motor to overwork when turning the blades. You can tell whether the edge is sharp or blunt by observing the tips of the cut grass; if the cutter is dull, the ends will be brown and tattered.

Check whether the blade is chipped, warped, or bent before sharpening it. Sharpen the edge if it is in good condition; otherwise, replace it. It is essential to use the blades that the manufacturers recommend ensuring safety.

Please take note of any vibrations while operating the lawnmower since they may indicate that the blade requires some TLC.

Keep the deck clean

Ensure that grass clippings do not accumulate beneath the mower deck to minimize rusting. If you use water to clean your machine after mowing, ensure that you dry the deck after rinsing it. You can use a blower to remove build-up on hard-to-reach areas.

Change the fuel

It is recommended to change the fuel every few months. If you let the gas sit in the engine for more than a few months, the old gas can degenerate inside the carburetor, thus clogging it. The expired fuel can also damage the fuel lines and seals.

Running the remaining gas out of the mower or draining it at the end of a mowing season will protect your lawnmower from damage that might result from keeping old fuel in the mower.

Add a fuel stabilizer

Fuel stabilizers slow down the unpopular gasoline oxidation process. If you do not use your lawnmower regularly, it is suggested to add a fuel stabilizer to the fuel to slow down its break-down. 

It is advisable to add a fuel stabilizer to fresh gasoline rather than gasoline that has stayed for more than 30 days as it may already be stale. Therefore, it would still be important to run the gas left in your mower at the end of the mowing season, then fill the tank with fresh gas and add the stabilizer.

In closing

Mechanic working on lawn mower

A well-functioning lawnmower exponentially reduces the effort required to maintain your lawn. Knowing why the engine fails will help you prevent its potential failure through frequent maintenance. Additionally, you will detect any issues with your mower before it fails.

It is advisable to let the motor cool after use. Further, ensure that you store the mower in a cool place. Also, drain the fuel before storage to keep it from aging and rusting the engine.

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Can You Use Car Motor Oil In A Lawn Mower? 

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