Lawn Mower Engine Makes Popping Sound: Reasons and Fixing Tip

Did you hear the Lawn Mower Engine Popping Sound? Well, this could seem dangerous. Relax because the backfiring or popping sound made by your mower engine is not serious but it does point to other issues that need to be addressed immediately.

So what exactly is this popping sound and why is it caused? Also, what can be done to fix it? Get all the information in this article.

What is Popping Sound on Lawn Mower?

A popping noise or a backfire is caused when the gasoline ignites outside the engine’s combustion chamber. Your mower may be working properly with no trouble and then you unexpectedly hear the backfiring. This explosion can distress you but there is nothing to worry about. However, if left unattended, then the cause behind this backfire could get hazardous for your mower engine.

You must delve deep to figure out what caused the engine to backfire. Once you understand the cause, fix it so that your mower can work normally again.

The popping sound usually occurs when you turn the engine on or off. Having some basic information about the popping sound and ways to deal with it does help.

Why did My Lawnmower Engine Make a Popping Sound?

What is the engine popping noise

The mower engine is a small combustion engine placed internally. Power gets produced in this combustion engine through the air-fuel mix combustion. This power production can take place in the 2-stroke and the 4-stroke engine. In both cases, it is the air-fuel mixture combustion that creates a spark to ignite the moisture which causes an explosion and releases energy.

The fuel combustion takes place in the combustion chamber in a controlled environment. If the fuel burns elsewhere then this causes a popping sound.

The popping or the backfire sound is heard when the fuel comes in close contact with the spark outside of the engine combustion chamber. The sound could be caused because of a problem with the fuel or the engine.

1. Fuel Related Issue and Fix

Fuel related issue and fix

There is fuel in the engine combustion chamber that needs air or oxygen to burn. Every engine is designed to get the right mixture of air and fuel in the combustion. All the strokes need to be perfectly timed for complete fuel combustion, smooth operation of the machine, and maximum release of energy. If there is an incorrect proportion of the air-fuel mixture then this causes many problems like the engine burning up smoke.

The timing of all the processes in the combustion chamber is important. If a process happens early or late then this causes problems. If there is an incorrect proportion of air-fuel mixture then this disrupts timing.

If there is a lot of air in the combustion chamber the engine does not create a spark because there is enough power to ignite the fuel for some time. The ignition is delayed but the other processes occur in their regular way. This makes the fuel pool in the low spots with the exhaust. The fuel gets ignited outside of the combustion chamber that produces an explosion or a popping sound.

At times the fuel escapes the engine’s cylinder before the valve closes. This could also occur during the exhaust stroke and then the fuel enters the exhaust or the engine. If there is a good amount of unspent fuel that enters the engine and comes in close contact with the spark then this makes it ignite and causes the engine to make a small popping sound.

In a nutshell, if the fuel combustion occurs anywhere apart from the combustion chamber in the engine or the exhaust then this will cause the popping sound.

How to fix it?

If the air-fuel mixture has more amount of air then this is called the low-pressure fuel. If the mower engine is backfiring then this could be because the low-pressure fuel is getting pumped into the combustion chamber of the engine. An old fuel pump or fuel filter could be causing low-pressure fuel.

All that you need to do to rectify the problem is to replace the old fuel filter and repair the fuel pump. If the problem was caused because of the low-pressure fuel then this will fix the issue.

2. Engine Related Issues

engine relating issue

The timing of the engine processes is crucial so that the mower functions smoothly. If there are some issues with the engine that mess with the correct timing then this will cause a popping sound.

Check the timing of the motor to see if the engine is backfiring. If there is an issue with the timing of the motor then this will cause the engine to ignite the fuel even though the internal valves are open.

After using the engine for a long there could arise a problem with the timing of the valve and the engine that could get disrupted. This could also occur because of a simple and basic chemical malfunction.

The problem should be fixed without delay so that the exhaust and engine do not get damaged further to become unrepairable.

How to fix it?

  • An engine tune-up restores the valves and the engine to its correct time setting. This will let both the valves open and close at the right time that and not let the fuel burn in the engine.
  • Spark plug cleaning or replacement helps. Just clean the plug chamber or the plug wire which will ensure the right timing of ignition thus preventing the backfiring sound.
  • Keep the fuel filter clean and replace it each year. Take guidance from your owner’s manual to understand which fuel is best for your mower.

Significance of Timing on Lawn Mower Popping Sound

Now that we have dealt with the issues that could cause an engine to backfire let us understand what significance does the popping sound timing hold.

During the start

LawnMower Start

If the lawnmower makes a popping sound when you start it then this indicates a damaged mower. Many mower parts safeguard the expensive parts. Like the flywheel will take damage to protect the expensive crankshaft. If your mower runs on a large rock then this can cause the flywheel to break and fail to engage causing the engine to make a popping sound when you start the mower.

A mower that has its flywheel broken will not start automatically. If the mower backfires then this indicates damage and you should take it for professional repair.

During the shut-off

Shutting LAwnMower Off

Sometimes you may hear the pop sound when you turn off the engine or when your mower is just lying idle. This happens when you slow down the engine fast. The speed of the engine builds up when it is in operation and when it is slowed down quickly then it pushes the gas in the muffler. This gas gets ignited and causes the popping sound.

To reduce the chances of such popping sounds you should reduce the mower speed gradually and let the motor stand idle for around 15 minutes before you turn the engine off.

Engine overheating is another reason why your mower is backfiring when you shut it off. Increasing the flow of air to the engine can reduce it from overheating. If you hear the popping sound during the shut-off and you feel that it could be because of an overheated engine then get in touch with a professional who will increase airflow to your engine.

After shutting the engine off

If your mower makes a popping sound after you have shut off the engine then this could be a problem with the muffler or the carburetor.

To fix it check the carburetor for any incorrect settings. Check the muffler if it is constructed wrongly. Rectifying these issues could solve the problem.

Also if you use the incorrect gasoline then this can cause the mower to backfire after it is shut off. Gasoline with alcohol will ignite differently than the one that does not contain alcohol. When the gas that contains alcohol gets ignited in the muffler then these causes backfire. In this case, switch to gas that contains low alcohol content or uses gas that does not contain alcohol at all and save yourself from the trouble.

Installing Anti-Backfire Equipment

anti-after-fire solenoids

There is special equipment that is attached to many mowers that prevent backfiring when the mower is shut down. These are called anti-after-fire solenoids. It is a great idea to install them that let you turn the engine off irrelevant of the speed and do not let the fuel shoot the muffler.

Final Thoughts

It sounds dangerous when your engine makes a popping sound. However, this is not something that you should be bothered about. Using the information provided above, you can figure out what caused the mower to backfire and then follow the recommended fix. It is however important to act fast to not cause any permanent damage to the mower.

However, if you have been noticing issues with your lawn mower for a long period, then read this article to know if you should repair or replace your mower: When to Replace Lawn Mower Or Should You Just Repair?

About Jennifer Igra

Growing up in Brooklyn, New York City known for it’s green gardens. Jennifer, a 30 year old gardener and green living fanatic started Igra World to share her gardening journey and increase gardening awareness among masses. Follow Igra World to improve your gardening skills.

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