Lawn mower slowly dies. Lawn mower backfires then dies

Why My Lawn Mower Stops Running After A While? Expert’s Interview

The lawn mower market is huge, and it is expected to exceed 23 billion dollars by 2023 globally. The maintenance of lawn mowers is an important task for gardeners. Unfortunately, gardeners often experience several problems while using this cutting tool. Have you ever wondered about this question: why does my mower keep dying?

Why my lawn mower stops running after a while?

Three things are necessary to run a lawn mower smoothly: fuel, air, and a spark. If your lawn mower lacks any of these three things or you failed to mixed them appropriately (not too much nor too little), your lawn mower may stop running after a while.

• Why My Lawn Mower Stops Running After A While?

• Grimy Or Damaged Spark Plugs
• Mower Running On Old Gasoline
• Choking Issue
• Faulty Gas Cap
• Clogged Or Dirty Carburetor
• Excessive Amount Of Oil
• Dirty Air Filter
• Power Supply Issue
• Mower Blockage Issue
• Defective Or Lack Of Sharpness Blades
• Compression Issue

• Fixing Carburetor Issue
• Fixing Gasoline Issue
• Fixing Spark Plug Issue
• Fixing Excessive Oil Issue
• Fixing Battery Powered Lawn mower

• Systematize Your Work
• Never Run Your Mower Without The Blade
• Follow The Instruction Manual

Why My Lawn Mower Stops Running After A While?

Why does my lawn mower shut off while mowing? It depends on various reasons as per your lawn mower. Here are them:

Grimy Or Damaged Spark Plugs

A spark plug does the job of igniting the air/fuel mixture in your engine by producing a “spark.” When spark plugs become grimy or damaged, it fails to do this function properly.

A dirty or damaged spark plug may prevent your lawn mower from starting or die after running for a while.

Mower Running On Old Gasoline

You can operate your lawn mower without gasoline. However, you can’t overlook the quality of the gasoline too.

When the gasoline has not changed for a long time, or the machine sits idle for several months, a damaging residue has probably been created due to evaporation.

Your mower becomes clogged by the residue left by this process. As a result, the gas can’t flow smoothly and freely.

It makes the machine die after running a short period every time you start it. Sometimes, you may even fail to run it even after trying to switching on it.

Choking Issue

Almost every lawn mower comes with a choke to alter fuel-to-air combination. As the mixture warms up, the engine runs continuously.

As long as there is no cooler temperature for some time, it is better to turn off the choke to stop the engine from being overfilled with the incorrect combination of fuel.

However, if you keep the choke idle for a long time, the combustion chamber might be overflowed with fuel. It will ultimately make it frozen and stalls.

Under this situation, you want to leave the lawn mower idea for a few hours. Fuel drains from the combustion chamber when it sits idle.

Turn off the choke and restart it, and check out whether you can run the mower smoothly.

Faulty Gas Cap

Another possible reason could be a faulty gas cap. Though several types of gas caps are available, vented gas caps are most common for lawn mowers.

Using a vent, the gas fumes in the tank can escape while air is allowed to enter. Occasionally, you may see the check valve is not working properly, and it doesn’t support the air to go through the tank. But you will not face any issue running the lawn mower normally.

As you know, mowers run through fuel. Without sufficient fuel, it can’t run for long. So a vacuum slowly forms in the fuel tank as the level of fuel falls. When the fuel is consumed, space is filled with air.

With 15-20 minutes, the vacuum becomes pretty hard. No fuel flow will occur to the carburetor, which will ultimately cause the lawn mower to stop after running a while.

Clogged Or Dirty Carburetor

Sometimes, the carburetor of your lawn mower can be the reason for this question: why my lawn mower stops running after a while?

It is a common scenario in colder areas, where your machine sits idle for several months. As a result, during the warmer months of the year, your mower will work harder.

Whatever the reason, you want to take care of the carburetor properly.

Without the right amount of air and fuel, you can’t run your mower smoothly, and a carburetor ensures this accurate mixture.

If the carburetor becomes dirty or has some clog-up issues, it fails to do its function. Therefore, your lawn mower may stop running after a while.

Excessive Amount Of Oil

Oil is necessary to run a lawn mower smoothly. But that doesn’t mean you will keep more than needed oil in the tank.

So, what is the possibility to determine you have kept too much oil or not? When you do not see any of the reasons mentioned above, it can be associated with this problem.

The engine will emit white smoke when it is overheating due to excessive oil. It’s possible that the mower maybe works if smoke is evaporating in significant quantities.

However, you can only run the machine for a few minutes, and it will stop after a while. Excessive oil breaks down the function of the machine and stops it from working smoothly.

Dirty Air Filter

When you want to know why my lawn mower stops running after a while, the dirty air filter can be one of the reasons too.

You want to make sure the right level of air enters inside the gasoline for the ignition process. Unfortunately, when the air filter becomes excessively dirty, you can’t expect unrestricted airflow.

Power Supply Issue

Sometimes, the question of why does my lawn mower shut off while mowing may be related to a battery-powered lawn mower.

Do you always keep the mower plugged in a while using it or only use it after giving it full charge? Whatever the reason, you want to ensure there is no power as you are not using fuel to operate it.

Mower Blockage Issue

A lawn mower may stop after a while if there is any blockage issue by long grass or grass clippings.

Sometimes, the blades of the lawn mower can be clogged up by grass clipping. When you run the machine for several minutes, grass clippings prevent the blade from cutting grass. It ultimately stops the machine from working.

Similarly, excessive long grasses can also block the mower from running and even break it down.

Defective Or Lack Of Sharpness Blades

Cutting thicker grass requires sharp blades for mowers. If there is no sharpness on blades or they have become defective, you can’t cut the grass properly. As a result, the machine will stop after cutting for a while.

This could also happen if blades are loose. So make sure you attach the blades before cutting the grass.

Compression Issue

Are you still wondering about this question: why my lawn mower stops running after a while? When your lawn mower doesn’t have any of the issues mentioned above, it might have a compression problem.

Under this situation, the mower gets hot, a slight change occurs in the valve’s shape and reduces the engine’s efficiency.

Not everyone can figure out this issue because you need professional knowledge to find out the compression issue.

So, these are all the possible reasons when you want to know why my lawn mower stops running after a while.

How Do You Fix A Lawn Mower That Won’t Stay Running?

Fixing a lawn mower is essential to ensure optimum performance while cutting the grass. You can’t use a lawn mower that often stops while cutting.

So, you have already known what would cause a mower to start but not stay running. Now, let’s find the answer to this question: how do you fix a lawn mower that won’t stay running.

Here one thing you should remember that different lawn mower has different issues. So solutions will be varied based on the problem. That’s why we are going to disclose all possible solutions on what would cause a mower to start but not stay running.

Fixing Carburetor Issue

You have already learned that carburetor may become dirty or clog up. In order to deal with the dirty carburetor, you can use a carburetor cleaner such as WD-40 for super cleaning.

First of all, unscrew the carburetor bowl and then clean each part of it by spraying the solvent on the surface. After spraying the cleaner, use fabric to clean out dirt, grease, or any carbon contaminants.

Fixing Gasoline Issue

Mixing new gasoline with the old gasoline may make formula impure if the old gasoline has a larger quantity than new gasoline. So, you want to add fresh gasoline.

One of the best things you can do is buying a stabilizer to overcome the jamming up of the issue. You will find a wide range of stabilizers are available in the market. You can use the Star Tron Enzyme Fuel Treatment or a decent one you prefer.

over, it will cost less than 10 while using it for up to 2 years. Finally, don’t forget to go through instructions to find the balance between the fuel and stabilizer in your mower.

Fixing Spark Plug Issue

Spark plugs are a handy tool, which you will easily find in nearby hardware shops. If your lawn mower spark plug becomes excessively dirty, you can use a decent cleaner with a stiff brush to clean them. However, avoid using any shot-blasting cleaner as it can lead to serious health issues.

On the other hand, if a tangled heap of carbons appears on your mower’s spark plug, replacement may be a better option. They are low-price and easily accessible, and you shouldn’t struggle to replace a new one.

Most experts suggest replacing the spark plug for each season or at least after two seasons. It will ensure you are using a trouble-free lawn mower.

Fixing Excessive Oil Issue

When your lawn mower oil tank has excessive oil, you may face difficulty running it. In that case, the solution is hassle-free straightforward.

You just remove some oil from the tank using a siphon. One tip is to add oil gradually. Before overfilling the tank, check out the dipstick position and add oil slowly. If you fear overfilling it, avoid making it full.

Fixing Battery Powered Lawn mower

Are you using a battery-powered lawn mower? In that case, you want to ensure sufficient charging while cutting the grass.

For long-lasting charge, you can use a Smart charger. Plus, when you don’t use the mower for several months, remove the battery from the machine and keep it separately in a safe place.

Lawn mower Stops After A While: How To Know When To Hire A Professional?

We have already shared all the possible issues you may encounter on what would cause a mower to start but not stay running. Also, we included several solutions, and we are expecting you have solved the issue by trying each of them.

However, if you failed to deal with the issue, it is best to call for a professional. Some other possible problems could be a faulty choke, gas tank or gas line blockage, etc.

When the problems are too complicated, professionals are the best choice. Unless you are extremely handy, you may end up damaging another part instead of fixing them.

In addition, if your lawn mower has a warranty, don’t forget to seek the manufacturer’s help. After all, it will be cost-free, and you can relieve yourself of mess.

On the contrary, if there is no warranty left for the mower, contact a nearby local shop that is popular in the area. Tell them everything about the kind of problems you are facing.

How To Prevent Lawn Mower Issues?

You have already learned why my lawn mower stops running after a while and what the possible solutions you can apply are.

Though engines are supposed to show issues after a specific time, you still want to take care of them appropriately to delay the problems.

The following tips will help you avoid lawn mower issues.

• Use a carburetor cleaner spray to keep your carburetor clean and efficient.
• You can use an engine degreaser because cleaning your engine will be easier with it.
• The oil tank should not be overloaded. You can use a dipstick to eliminate the issue.
• Don’t forget to clean the air filter regularly to prevent blockage issues.
• Changing lawn mower spark plugs after each season or at least after two seasons is a better follow-up.
• Make sure the gasoline and oil inside the tank are not too old and dirty. Using a stabilizer is a better option to keep gas fresh.
• Always keep the lawn mower engine clean after cutting the grass. It will prevent grease and dirt build-up.
• Make sure no screws or nuts are loose for any parts of the mower.
• It is best not to cut wet grass as it may cause clogged issues.
• As per your cutting frequency, it is better to sharpen the blades for smooth cutting.

Systematize Your Work

Before following a particular solution, you want first to figure out why my lawn mower stops running after a while. If you failed to figure out the type of issues you are having, you might follow the wrong solution.

Nevertheless, you are free to try each solution to remove the issues though it is time-consuming. In that case, apply the simple and straightforward solutions first and then go to complex ones.

You first want to tell yourself whether you are comfortable handling the situation of your own. As the procedure can be complicated, you may not be familiar with the basics. In that case, taking professional help is a better option to save time, effort, and hassles.

Never Run Your Mower Without The Blade

One of the most common mistakes many gardeners made is starting the mower without the blade. Aluminum flywheels are mainly used for lawn mowers, and the extra blade weight is part of the system that powers the flywheels.

As you know the basics of how a lawn mower works, the system will experience an increase in inertia due to this.

You will face difficulty starting the machine without blades due to a lack of spin momentum when switching on the machine.

Follow The Instruction Manual

Different lawn mower functions differently. You may need to follow a different method to take care of your mower.

In that case, following the instructions provided by the manufacturer is the best way to proceed. The more you stick to their guidelines, the better lifespan for the machine you can ensure.

Try to avoid any actions which are asked to. Following wrong guidelines may damage the mower or reduce the efficiency of the machine.

Conclusion

It is not a trouble-free job to maintain your lawn mower. But when you regularly do the maintaining job, you can prevent frequent occurring issues.

Ensure you always wear hand gloves while working on the mower engine to keep your skin safe from oil and gas.

Remember, if you don’t have enough knowledge of what you are doing, you shouldn’t do it. Consider getting expert help to solve the problem. Doing it yourself may damage some essential systems or parts of the mower.

Hopefully, you have gotten the answer to this question: why my lawn mower stops running after a while?

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Last update on 2023-01-28 / Affiliate links / Images from Amazon Product Advertising API

Lee Safin was born near Sacramento, California on a prune growing farm. His parents were immigrants from Russia who had fled the Bolshevik Revolution. They were determined to give their children a better life than they had known. Education was the key for Lee and his siblings, so they could make their own way in the world. Lee attended five universities, where he studied plant sciences and soil technologies. He also has many years of experience in the U.S. Department of Agriculture as a commercial fertilizer formulator.

Thoughts on Why My Lawn Mower Stops Running After A While? Expert’s Interview

Lawn mower backfires then dies

Lawn mower backfires then dies. A backfire in a lawnmower is just like a small blast. Mostly it is not threatening, but the reasons behind this blast are dangerous for the engine.

Backfires occur surprisingly and mostly when you are switching on the lawnmower or switching off it after completing the work.

It is very important to know the basic information related to the backfire problem and how you can deal with it properly. It generally happens when the fuel approaches the spark from outside of the engine burning chamber.

If enough amount of unused fuel runs to enter the engine and approaches to spark, then it will catch fire, producing a small engine blast.

There are many reasons behind the lawn mower backfiring, mostly when it is overheated. So without any wait, let us discuss all possible problems and how we can fix them to save our mower from backfiring.

Lawn mower backfires then dies

Normally, a mower backfires means that there is additional air in the gas mix, which will lead to unfinished combustion. The gas that is sent to the exhaust will still hold gas.

When it approaches the exhaust, the gas will exnight impulsively and makes a big sound which is called backfire.

Here I explain the main issues of the lawnmower when it backfires.

Decreasing the speed of the engine fastly

It is a very important fact that you are if you are running a mower for one hour, then lowering the speed of the engine fastly can cause a backfire because the mower is already very hot.

So its only and simple solution is that slowly decrease the speed of sound.

Lawn mower fix. (won’t start, backfires through carburetor)

Low-pressure fuel

Low-pressure fuel basically means that air is mixed in more amounts in the air-fuel mixture. If a mower is backfiring, then the reason behind it could be that the low-pressure fuel is pushed into the engine burning chamber.

Old fuel filters and faulty fuel pumps are the main causes of low-pressure fuel.

So you should change the old fuel filters and repair faulty fuel pumps. Your problem of backfiring the mower will be fixed if these are the causes behind this issue.

Backfire when switching on the engine

It is a very rare case to face a backfire when starting the engine. However, if it occurs, then possible it is an issue with the carburetor or with the Firewheel.

If the carburetor malfunction, then the engine will not start. The backfire will occur because of the flooding in the engine, and it is not hot to still catch fire in the exhaust.

If the engine of the mower still starts, then it influences the timing of the engine because the oil will start leaking because of the damage.

Clean the spark plug

If there is a clog in the spark plug, then clean its wires and chamber.

It will make sure that ignition will happen at the proper time and stops the backfires, which usually occur due to untimed ignitions.

Clean the fuel filter

It is also very necessary to clean the fuel filter of the lawnmower. If you have been using it for one year, then it is better to replace it.

Sticky valves

The basic purpose of the valves is to seal off the cylinder in the engine. Air and gas mixture is entered into the cylinder by opening one valve.

At the same time, the other valves are opened to exhaust gases to way out from the cylinder after the process of combustion.

Now, if these valves take some time to open, then these gases can backfire. These valves are an internal part of the engine, so it is not possible for you to repair or replace them.

So it is best for you to open and let this job be done by the professional who will open the engine and repair the valves.

Conclusion

The final thought on this topic is that the backfiring of a lawnmower is not a great thing to worry about because it is something like a small explosion.

If you want to prevent your mower from this troubleshoot,ing then take care of small things like slowing down the speed of the mower slowly.

There should be no fault or clog in the spark plug. If you can not be able to solve the problem, then hire a professional.

Related Guides

Lawnmower Won’t Start? Do this.

A lawnmower that won’t start, especially when taken from storage, is almost always due to one problem: bad gas.

Storing a lawnmower in the fall without adding gasoline stabilizer to the fuel tank can cause the fuel to break down and plug the fuel passages. If fixing that problem doesn’t help, there are a few others that can help fix a lawnmower that won’t start, as we explain here.

How to Fix a Lawnmower That Won’t Start

Replace the Bad Gas

Over time (like the six months your lawnmower sat in your garage over the winter), the lighter hydrocarbons in gas can evaporate. This process creates gums and varnish that dirty the carburetor, plug fuel passages and prevent gas from flowing into the combustion chamber.

The carburetor bowl below formed corrosion and deposits during storage, which can easily plug fuel passages and prevent the engine from starting.

Storing equipment without stabilizing the gas can lead to deposits that foul the carburetor or injectors.

Ethanol-containing gas can absorb water from the atmosphere, which can lead to phase separation, which occurs when ethanol and gas separate, much like oil and water. Ethanol that has absorbed enough moisture and has sat long enough can foul the fuel system and prevent the engine from starting.

No matter how many times you yank the pull cord and pollute the air with your advanced vocabulary, the lawnmower won’t start if it’s trying to run on bad gas.

In extreme cases, evaporation of lighter hydrocarbons can change the gasoline’s composition enough to prevent it from igniting. The gas may be fueling the engine, but it doesn’t matter if it won’t ignite.

Bad Gas in Your Lawnmower? Here’s How to Fix It

If you neglected to add gasoline stabilizer to the fuel prior to storage, empty the tank and replace with fresh gas. If the tank is nearly empty, simply topping off with fresh gas is often enough to get it started.

On some mowers, you can easily remove and empty the fuel tank. Sometimes that’s more trouble than it’s worth. In these cases, use a fluid extraction pump or even a turkey baster to remove the bad gas. You don’t need to remove all of it; but try to get as much out as possible.

Clean the Carburetor

You’ve replaced the fuel, but your lawnmower still won’t start.

Next, try cleaning the carburetor. Remove the air filter and spray carburetor cleaner into the intake. Let it sit for several minutes to help loosen and dissolve varnish and gums.

Remove the air filter and spray carburetor cleaner into the intake. Let it sit a few minutes to loosen deposits.

On some carburetors, you can easily remove the float bowl. If equipped, first remove the small drain plug and drain the gas from the bowl. Remove the float bowl cover and spray the float and narrow fuel passages with carburetor cleaner.

This kind of “quick-and-dirty” carburetor cleaning is usually all it takes to get the gas flowing again and your lawnmower back to cutting grass.

If not, consider removing the carburetor from the engine, disassembling it and giving it a good cleaning. Be forewarned, however: taking apart a carburetor can lead to nothing but frustration for the uninitiated. Take pictures with your phone to aid in reassembly. Note the positions of any linkages or the settings of any mixture screws, if equipped. If you’re at all reluctant, visit the servicing dealer instead.

Consider replacing the carburetor altogether. It’s a fairly simple process on most smaller mowers and it’s often less expensive than taking it to the dealer.

Direct compressed air from the inside of the air filter out to remove debris that may be reducing airflow and preventing the lawnmower from starting.

Clean/Replace the Air Filter

With the air filter removed, now’s the perfect time to clean it.

Tap rigid filters on a workbench or the palm of your hand to dislodge grass clippings, leaves and other debris. Direct compressed air from the inside of the filter out to avoid lodging debris deeper into the media.

Use soap and water to wash foam filters. If it’s been a few years, simply replace the filter; they’re inexpensive and mark the only line of defense against wear-causing debris entering your engine and wearing the cylinder and piston rings.

An incorrectly gapped spark plug can prevent the engine from starting. Set the gap to the specification given in the owner’s manual.

Check the Spark Plug

A dirty or bad spark plug may also be to blame. Remove the plug and inspect condition. A spark plug in a properly running four-stroke engine should last for years and never appear oily or burned. If so, replace it.

Use a spark-plug tester to check for spark. If you don’t have one, clip the spark-plug boot onto the plug, hold the plug against the metal cylinder head and slowly pull the starter cord. You should see a strong, blue spark. It helps to test the plug in a darkened garage. Replace the plug if you don’t see a spark or it appears weak.

While you’re at it, check the spark-plug gap and set it to the factory specifications noted in the lawnmower owner’s manual.

If you know the plug is good, but you still don’t have spark, the coil likely has failed and requires replacement.

Did You Hit a Rock or Other Obstacle?

We’ve all killed a lawnmower engine after hitting a rock or big tree root.

If your lawnmower won’t start in this scenario, you probably sheared the flywheel key. It’s a tiny piece of metal that aligns the flywheel correctly to set the proper engine timing. Hitting an immovable obstacle can immediately stop the mower blade (and crankshaft) while the flywheel keeps spinning, shearing the key.

In this case, the engine timing is off and the mower won’t start until you pull the flywheel and replace the key. It’s an easy enough job IF you have a set of gear pullers lying around the garage. If not, rent a set from a parts store (or buy one…there’s never a bad reason to buy a new tool) or visit the dealer.

My Lawnmower Starts But Runs Poorly

If you finally get the lawnmower started, but it runs like a three-legged dog, try cleaning the carburetor with AMSOIL Power Foam. It’s a potent cleaning agent designed to remove performance-robbing carbon, varnish and other gunk from carburetors and engines.

Add Gasoline Stabilizer to Avoid Most of These Problems

Which sounds better? Completing all these steps each year when your lawnmower won’t start? Or pouring a little gasoline stabilizer into your fuel tank?

Simply using a good gasoline stabilizer can help avoid most of the problems with a lawnmower that won’t start.

AMSOIL Gasoline Stabilizer, for example, keeps fuel fresh up to 12 months. It helps prevent the lighter hydrocarbons from evaporating to reduce gum and varnish and keep the fuel flowing. It also contains corrosion inhibitors for additional protection.

I have a five-gallon gas can in my garage from which I fuel two lawnmowers, two chainsaws, two snowblowers, a string trimmer, an ATV and the occasional brush fire. I treat the fuel with Gasoline Stabilizer every time I fill it so I never have to worry about the gas going bad and causing problems.

You can also use AMSOIL Quickshot. It’s designed primarily to clean carburetors and combustion chambers while addressing problems with ethanol. But it also provides short-term gasoline stabilization of up to six months.

Use a Good Motor Oil for Your Lawnmower

Although motor oil has no bearing on whether your lawnmower starts or not (unless you don’t use oil at all and seize the engine), it pays to use a high-quality motor oil in your lawnmower.

This is especially true for professionals or homeowners running expensive zero-turn or riding mowers.

Lawnmower engines are tougher on oil than most people realize. They’re usually air-cooled, which means they run hotter than liquid-cooled automotive engines.

They often run for hours in hot, dirty, wet conditions. Many don’t have an oil filter, further stressing the oil.

In these conditions, motor oils formulated for standard service can break down, leading to harmful deposits and reduced wear protection.

For maximum performance and life, use a motor oil in your lawnmower designed to deliver commercial-grade protection, like AMSOIL Synthetic Small-Engine Oil.

Its long-life formulation has repeatedly demonstrated its ability to safely exceed original equipment manufacturer (OEM) drain intervals in the toughest conditions. It provides an extra measure of protection when equipment goes longer between oil changes than is recommended by the OEM.

My Lawn Mower Starts Then Dies: What’s Wrong?

Affiliate Disclaimer: My content may contain links to products I use and love. As an Amazon Associate and participant in various other affiliate programs, I earn a small commission at no extra cost to you from qualifying purchases. I only recommend products I personally vetted!

We’re all guilty of leaving our lawns to become a little, shall we say… unkempt at times.

But, “It’s okay”, we tell ourselves, even as it verges on jungle-level overgrowth, because any day now, we’ll get a spare moment to unleash the mower and tidy things up.

And sure enough, we do eventually find time to give our yards some long-overdue TLC, but just as we reach the halfway point, with thoughts of a sudsy post-job cold one rattling around our brains, something else starts rattling… the lawn mower.

It sputters on for another couple of yards before giving up the grassy ghost, leaving us with half a putting green that Tiger Woods would applaud, and half a dense rainforest that not even Bear Grylls would dare enter.

Half a trimmed lawn is like half a haircut — not socially acceptable, and, frankly, terrible-looking. What are we supposed to tell the neighbors?

“Oh, yeah, sorry about this, Val, my erm… my lawn’s going through a bit of a punk rock phase at the moment” — Somehow, I don’t think that’s going to track.

Nope, the only option is to get that lawn mower going again, and to do that, you first need to identify the problem, and, secondly, fix it, which is exactly what I’m going to help you with today!

Why Is My Lawn Mower Betraying Me?

When your lawn mower starts up but cuts out before you have a chance to get anything done, the usual suspects are…

• A dirty carburetor or an obstruction in the carburetor bowl
• Stagnant gasoline
• Damaged or dirty spark plug(s)
• Excessive oil levels

That may seem like one hell of a line-up, but I’m happy to report that they’re all incredibly easy to fix, and I’m going to show you how.

Carburetor Chaos

Besides being incredibly difficult to spell, the carburetor is your lawn mower’s most important component, so when your grass-eating beast starts to misbehave, all eyes should turn to the carb.

I Thought Only Old Cars Had Carburetors. What Are They Doing in Our Lawn Mowers?

The carburetor in your lawn mower does the exact same thing it does in your car: Mixes precisely the right amount of gas with precisely the right amount of oxygen to facilitate combustion.

These tiny controlled explosions spark a chain reaction that gets the crankshaft spinning and the engine fired up, but if the fuel:oxygen ratio is off due to a buildup of dirt on the carburetor or a clogged bowl, it can throw the whole system out of whack.

Combustion will still be taking place, which is why your lawn mower fires up when you pull the cord, but it’s not a sustainable power source, which is why your mower chokes moments later.

Okay, So How Do I Fix It?

In this scenario, all you need to do to revive your lawn mower is give the carburetor a thorough clean, and what better to do that with than an aerosol can of specialized carburetor solvent?

I can personally recommend WD-40 Specialist Carb/Throttle Body Parts Cleaner. It’s super affordable, and takes care of both carbon contaminants and gumming. I’ve been using it for years, and it’s never let me down.

That said, it does have one shortcoming… it lacks a straw applicator for precision use, but that’s okay, as there are many alternatives that do, such as Gumout Carb and Choke Cleaner. I’d advise you to pick up a can of both, use the WD-40 for the heavy lifting, then switch over to the Gumout for precision spot cleaning.

Step 1. Open The Windows

Carb cleaner may be great for your carburetor, but it’s hell on the lungs, so make sure you’re working in a well-ventilated area.

Step 2. Finding The Carb

Your carburetor will either be bolted to the top or side of the motor. Found it? If not, check behind or below the air filter.

Step 3. Remove The Fuel Line

Detach the fuel tank from your mower (they usually slide out of place), then use a pair of needle nose pliers to shimmy the fuel line loose.

Step 4. Remove And Clean The Jet Screw

The jet that feeds fuel into the carb doubles up as a bolt that holds the bowl in place. Unscrew the jet from beneath your carburetor, and give it a generous spritzing with your carb cleaner.

I find it’s best to use the precision applicator for cleaning the jet channels, as the concentrated stream can help dislodge debris.

For the best results, you should consider using a carb cleaner kit, as they arrive with all the special brushes you need to rejuvenate your jet.

Step 5. Poke The Jet Channels

Take a piece of wire, or even just an unfolded paper clip, and poke it through the tiny holes in the jet screw, just in case the carb cleaner missed anything.

Simple-Why Your Mower Dies & Stops Running #BALDEAGLE242

Step 6. Remove And Clean The Bowl

With the jet removed, the carb bowl should pull free. Spray it with plenty of carb cleaner, and, if you have one, give it a good scrub with the brushes from your carb cleaning kit.

Step 7. Check The Gaskets

The gaskets are the black, rubber O-rings that seal the discrete sections of your carburetor. Check for any crumbling or blemishes. If you find any, replace them with fresh gaskets.

Step 8. Push The Float

When you removed the bowl, you revealed the carb float, a little disk attached to the rest of the motor. Gently push it up and listen closely. If you hear a quiet clicking sound, all is well. If not, you may need a specialist to look into the matter.

Step 9. Put It All Back Together

Okay, so now your carb is looking slick and shiny, it’s time to re-assemble. Be sure not to overtighten the jet screw, as you might strip the threads and disfigure the seal.

Step 10. Spray Some Carb Cleaner In The Intake Hole Of The Engine

The intake hole is usually behind the air filter. Give it a light spritzing, and when you start your mower up, it will be pulled through the system, giving everything one last clean.

Step 11. Take Your Mower For A Spin

With any luck, that quick maintenance session solved your mower mishap, and now you’re free to cut all the grass you want. If it didn’t work, don’t sweat it. We’ve got three more fixes to try.

Geriatric Gasoline

You may not realize it, but just like those plums shriveling up in your fruit bowl, gasoline has a shelf life. Over time, the volatile compounds essential to combustion thin out, which, understandably, can have a negative effect on engine efficiency.

When the quality drops below a certain threshold, it starts to damage the internal components of your motor. What’s more, it leaves gummy deposits on surfaces, which, if left unaddressed, can impede gas flow, leading to, you’ve guessed it… sudden mechanical failures.

Got it! But How Do I Fix It?

If you’ve got, say, less than half a tank left, you may be able to get away with diluting it with fresh gas, thereby strengthening the combustive properties. But if you’ve got more than half a tank left, I’m afraid you’re going to have to dispose of the contents (responsibly, of course).

See also my guide on the type of gas to use for your lawn mower

No matter which route you end up taking, my advice is to throw some sort of fuel stabilizer into the mix, and if you’re looking for a recommendation, in the past, I used STA-BIL 360 Protection Ethanol Treatment and Fuel Stabilizer. This stuff prevents corrosion and halts the buildup you’ll see using traditional fuel, ensuring your engine always runs buttery smooth!

Alternatively, you could do what I do now and use TruFuel-4-Cycle Ethanol-Free Fuel. Ethanol is the stuff that causes all the problems when fuel stagnates, so removing it from the equation is kind of a no-brainer.

A tank full of TruFuel will survive a long, cold winter in the shed, so when the warmer weather arrives, and your grass gets a growth spurt, you can break out the mower sans hiccups!

Cards on the table, TriFuel is a little more expensive than the standard gas/stabilizer combo, but in my opinion, the reliability and peace of mind it brings is well worth the premium. It gets my 140cc BlackDecker mower fired up with a single pull every single time — a real shoulder saver!

Spark Plug Panic

Once the carburetor has mixed the fuel and air, it’s the spark plug’s time to shine.

These incendiary little components provide the spark that ignites the fuel/air cocktail, thereby powering your mower’s engine

As a pivotal part of the combustion process, should they fall into disrepair or perhaps get a little dirty, it can cause the irritating start-stop mower behavior that brought you to this article.

And What About the Fix?

As long as your spark plug isn’t completely coated with a stubborn carbon build-up, you can simply remove it, give it a thorough clean, then replace it. Hopefully, that will smooth the combustion process out and return your mower to its former glory.

If you do find a lot of soiling on your spark plug, it’s best to call it quits and order a new one.

Step 1. Locating Your Sparky

Spark plugs are typically front and center on your mower, so they’re not difficult to find. Look for a component covered with black cabling at the front end of the engine.

Step 2. Removing Your Spark Plug

Removing your spark plug requires a socket wrench of a certain size, so have a quick thumb through your user manual, and see what info you can dig up.

Don’t worry if you’ve misplaced your manual, as you can purchase a universal spark plug wrench here.

Once you’ve got the necessary tool, pull the black cable free from the plug, and use the wrench to unscrew it from the engine.

Step 3. Cleaning Your Spark Plug

I use standard multi-use WD-40 and a small wire brush for cleaning my spark plugs.

Start by spraying the plug down with your cleaning solution, then leave the chemicals to work their magic for a few minutes. Next, take your small wire brush, and give your sparky a good scrub to dislodge any dirt or carbon residue.

Once the debris has been agitated, wipe it away with a soft rag to wrap this step up.

Step 4. Replacing your spark plug

If you’re refitting your old spark plug, simply insert it into the end of your wrench and twist it back into place (not too tight).

Things are a little more complicated if you’re fitting a replacement plug, but stick with me, and we’ll have it sorted in no time!

• First, you have to “gap” the plug, which essentially means that you are thinning or widening the gap between the two electrodes at the end of the plug to suit the requirements of your mower. To do so, you’ll need one of these handy CTA Tools spark plug gappers.
• Check the recommended plug gap in your user manual, then run your spark plug gapper in the space between the electrodes. Turn it until you feel resistance, then check the measurement on the face of the tool.
• If the gap isn’t quite large enough, you can use the hole in the gapper to pry the top electrode upwards, as if you’re cracking the cap on that cold one you were dreaming of earlier (and still are). To make the gap smaller, all you have to do is use the gapper tool to push down on the top electrode.
• Once gapping is complete, you can set the plug in place as normal. Take your time, and don’t force it. You need to get the threads in just the right place to secure it properly, and remember, it shouldn’t be too snug, as overtightening can damage the plug seal.

Spark Plug Advice For The Future

A good rule of thumb is to switch up your spark plug at least once every two years, but I like to bump it up to once annually as part of my standard maintenance schedule.

Oil Overload

If you’re anything like me, you felt the urge to fill your oil reservoir to the brim. “Gosh”, you think… “Aren’t I a responsible machine owner!”, but surprisingly, there is such a thing as too much oil.

You may have noticed that before your mower decided to take a siesta, it was spewing some white smoke, which is a dead giveaway that you did get a little overzealous with your oil.

The reason your mower seems to be working fine at first is that the excess oil is yet to drown out the engine, and I know “drown” is a strong word, but this isn’t as grave a situation as it implies. Let’s take a look at how you can make things right again.

Fixing Your Oil Surplus

The easiest way to solve this issue with a walk-behind mower is to simply pop the top of your oil reservoir, tip your mower on its side, and drain some of the contents; however, this can get pretty messy.

A much cleaner way to reduce your oil level is to use an oil extractor pump. These things allow you to siphon the oil away without spilling it, meaning (as long as it’s clean) you can use it again at a later date.

Be careful not to extract too much oil, though, as that can be even worse for your lawn mower than overfilling it.

Once you’ve sorted your oil level out, fire your mower up and keep an eye out for the dreaded white smoke. If it seems to be running clear, then you’ll know the problem has been rectified, and you can even out your wonky lawn post-haste.

How To Prevent This Oily Issue Repeating Itself

Now that your motor is feeling its old self again, take a break, check the oil with your dipstick, and note down the level. You can use this for future reference.

When the time comes to replenish your oil reserve, the trick is to take it nice and easy. Instead of pouring your oil into the reservoir willy-nilly, pour it in a little at a time, pausing every so often to check the level with your dipstick.

None of These Fixes Worked. What Do I Do?

Lawn mower still giving you grief after trying all four of these fixes? Dang!

Starting and dying shortly thereafter can be symptomatic of more serious mower issues. They’re incredibly tricky to diagnose, and even more difficult to fix.

So, I’m afraid it might be time to bite the bullet, contact a specialist, and have them take a look at your mischievous machinery. The problem could be…

A Defective Choke

If it’s allowing the passage of too much or too little air, the engine won’t be working efficiently, and, in some cases, combustion may not occur at all, causing the sudden mower death we’ve been trying to resolve today.

A Spent Carburetor

Sometimes, no matter how much you scrub your carb, the damage is already done, and a replacement is the only way to get your grass gobbler purring again.

If you’re particularly handy, you may be able to make the switch yourself, but, in my opinion, it’s best left to a professional.

A Blocked Gas Line Or Tank

Engines require consistent fuel flow to run efficiently. Even minor disruptions in the gas feed due to internal blockages can transform your lawn mulching monster into a wheezing mess.

It takes some pretty invasive snooping to identify a blocked gas tank or line, so I’d recommend consulting a pro and paying them to do it for you.

Wait, Wait, Wait… Professionals? This Is Starting to Sound Expensive

I know you’re probably bracing your bank account for a severe hit, but if your mower is covered by a warranty, you may be able to get the manufacturer to fix it for you for free — hooray!

Some companies will even send an engineer to your door to either fix the mower right then and there, assess the issue and order parts, or collect it for repairs at a company service depot. You won’t have to lift a finger!

If your warranty has elapsed, or you never had one to begin with, it’s best to look for a small, reputable repairs shop in your area. These modest outfits are often staffed with highly experienced workers, and the are far less scary than you might imagine.

Lawn Mower Maintenance: Prevention Is Better Than the Cure

Before we go our separate ways, I thought it’d be a good idea to discuss some pro lawn mower maintenance tips, as the best way to ensure you’re never stuck with this issue again is to take good care of your machine.

• Clean your air filter — It’s common practice to clean a mower’s air filter once every 25 operating hours, so if it takes you 2 hours to mow your yards, it should be given a good once over every 12 ½ mows.
• Replace your air filter — I replace my air filter once annually, but if you have quite a lot of ground to cover, and you hit 300 operating hours before the new year, don’t hesitate to switch it out earlier than scheduled.
• Clean your carb — It’s generally recommended that you clean your carb around three times a year. I give mine some TLC once a season, excluding winter.
• Stabilize your gas — Unless you’re taking the TriFuel route (a wise choice), be sure to mix your gas with a fuel stabilizer, especially before putting your lawn mower into storage for the winter.
• Degrease and clean your engine — If you’re often up against long or wet grass, you should degrease and clean your lawn mower motor once a season, but, in most cases, twice a year is plenty.
• Try not to overfill your oil reservoir — Remember, your dipstick is your best friend!
• Replace your spark plugs — As long as you keep them clean, your spark plugs should last for 2 years.
• Find suitable storage — Your mower needs to be kept in a dry location, protected from the weather, but if you have no other option but to keep it outside, be sure to elevate it and cover it with a durable tarp.

Summing Up

And that brings us to the end of my mower guide. If you’re still here reading this, thank you for your time, but a part of me hopes you never even made it this far.

With any luck, one of the fixes mentioned earlier will have resolved your issues, and you’re now busy tidying up your yard before your fussy neighbor, Val, catches a glimpse and crosses you off her Christmas card list.