Lawn mower problems sputtering. 7 Reasons And 7 Fixes For Lawn Mower Sputtering

Reasons And 7 Fixes For Lawn Mower Sputtering

Regular maintenance regime is crucial to operate the mower properly, otherwise it can run into a number of issues and sputtering of fuel by lawn mower is just one of them.

If not serviced regularly, even the best of mowers like the Raptor, Craftsman, Dixon, Ariens, Simplicity, etc, can develop such an issue and die. It’s more common than you can imagine! That’s why, if your lawn mower sputters but runs, or won’t start, don’t cast out your mower as yet! It’s just a mechanical error and can be resolved with a few simple fixes.

“Your lawn mower sputters and dies, sometimes coughs, due to incorrect grade of fuel, clogged carburetor and fuel filters, dirty air filters, moisture in the fuel system and a faulty spark plug. It can also be caused by a clogged mower deck and a faulty fuel cap.”

With this article, you will learn

• What causes lawn mowers to sputter fuel ?
• Solutions to fix when the lawn mower sputters but won’t start
• Tips to prevent lawn mowers from sputtering fuel.

After finding out about the causes, decide whether it’s a DIY solution, or you would need some professional help!

Reasons Why The Lawn Mower Sputters When Running:

The engine (of your lawn mower) depends on the correct combination of fuel, air and the spark to combust and start.

So, if you’re figuring out,’ why is my lawn mower sputtering and backfiring?’ check all of these three i.e-the fuel, the flow of the air to the engine and the spark built on the engine. Any flaws in any of these can cause sputtering of fuel on the mower.

There can also be a few other reasons due to which the lawn mower sputters but won’t start. Let’s check them out.

Dirty Air Filters or Fuel Filters;

When the air filters or fuel filters are caked with dirt, the supply of air to the combustion chamber is blocked.

This is the biggest reason why the lawn mower sputters and dies because the fuel-to-air mix ratio in the combustion chamber shakes off!

The dirt can also settle on the opening ports of the filters and the carburetor and stop the fuel flow completely, which is another potent reason for sputtering on a lawn mower.

Old or Incorrect Grade of Fuel;

Most often, users find it convenient to fill the mower with the fuel available at a nearby gas station but this fuel has almost 10% ethanol. Yes, it’s cheaper than pure and premium gasoline but works best for cars, not the lawn mowers.

Ethanol burns very fast and can possibly melt the plastic parts of the engine which leads to sputtering in the mower.

Clogged Carburetor;

During combustion, the fuel releases hydro-carbons which leave gummy residue behind and clog the carburetor. This clogging blocks the apertures of the engine and the lawn mower will sputter but won’t start.

Also, incorrect blend of fuel and air makes the carburetor run roughly and the lawn mower sputters through the carburetor.

Faulty Fuel Cap;

If your lawnmower is sputtering and backfiring, the reason could be a faulty fuel cap with clogged vents or fits loosely on the tank.

If the vents of the fuel cap are clogged with dirt, air will not pass through it and reach the tank leading to the fuel becoming thicker and the engine will start smoking.

On the contrary, if the fuel cap is loose, the lawn mower will sputter but run. Then, it will keep leaking fuel and spill down on the blades along with parts of the ignition system and can cause a misfire.

Moisture in the Fuel System;

Moisture gets into the fuel system when condensation occurs. A loose fuel cap, as quoted above, is the reason for moisture in the fuel system. It can also occur if you use your mower on a rainy day. That is why, it is strictly prohibited to use the mower when it’s pouring or when the lawn is wet.

Due to moisture, the cylinder fails to ignite the fuel properly and no combustion takes place. Then, the lawn mower will sputter and won’t start.

Mower Deck Issues

This happens mostly when you mow a lawn with tall and damp grass. That makes the lawn mower sputter fuel due to caked grass on the deck.

Furthermore, check out my article for resolving more mower deck issues, along with tips to maintain a deck, that can occur on any lawn mower.

Faulty Spark Plug.

A faulty spark plug which is either broken or clogged with carbon, does not build spark to start the mower. The lawn mower sputters but won’t start if the firing pins of the spark plug are broken or the plug’s electrodes are too adjusted too wide.

Hence, this was about the reasons why your lawn mower sputters while running. Now, let’s learn how you fix these issues to avoid sputtering of fuel on the mower and prevent it from backfiring.

Solutions To Fix A Lawn Mower Sputters While Running

Check Whether the Fuel is Old or is Very Less;

• As explained above, the fuel stations have a fuel which has 10% ethanol, which is a big NO for a mower’s engine. So, invest in a non-ethanol fuel blend like VP Fuels.
• If your mower already has ethanol fuel or old fuel, drain the entire fuel out and fill in fresh fuel. Also, add in fuel-stabilizer to maintain fuel’s efficiency and performance.
• While you do this, check the fuel pump. Change the pump if it’s leaking fuel.

Fix Moisture Issues on the Mower.

• Remove the fuel cap and check for droplets of water. Before water gets into the tank, it will surface on the fuel container in the form of droplets.
• You can also identify water in the tank if the liquids in the fuel tank are separated or have different colours.
• If there is water, drain the fuel out and add in fresh fuel.
• To prevent moisture from getting into the tank again, change the loose fuel cap.

( Dispose off the disposed fuel carefully as it’s very flammable.)

Clean the Dirty Air and Fuel Filters;

• Sputtering can occur on any lawn mower, be it old or new. Be it a Briggs and the Statton lawn mower sputtering or the toro lawn mower sputtering, you can do two things- either clean the filters or change them with new ones.
• The mower’s filters can be cleaned if they’re moderately dirty.
• If your mower has filters made up of foam, wash them with warm water and gentle liquid soap. Dry them completely before you attach them again.
• But if the mower has paper filters, it’s better to change them.

Clean the Carburetor and Adjust it Correctly.

During regular usage, the carburetor builds up fuel gunk over it and clogs up. A clogged and incorrectly adjusted carburetor is one of the reasons why a lawn mower can sputter fuel.

• Clean the carburetor using a carb cleaner and make it a routine affair.
• After you remove the dirty carburetor and replace a clean one, remember to install and adjust it correctly.
• To rebuild the carburetor, either refer to the mower’s manual, or for this, you can seek professional help.

Change the Spark Plug if it Doesn’t Build Spark;

• Clean the spark plug’s firing tip using a wired brush.
• Set the correct gap between the electrodes and the metal on the spark plug. Refer to the mower’s user manual to learn the recommended gap but ideally, it should be between 0.028-0.031 inches.
• If the spark plug has broken porcelain housings, it’s best to change the spark plug.

Check if the Fuel is Sputtering Out from Cracked Fuel Lines;

• If the lawn mower sputters while it runs, check the fuel lines for any cracks.
• When the fuel lines become brittle, they can crack down easily. Change the fuel lines if they have any tiny holes or cracks.
• Also, check that the fuel lines are securely closing on the fuel tank otherwise they can keep spilling tiny amounts of fuel, which can cause a misfire on the engine.

Clean the Caked Grass on the Dirty Mower Deck.

Your lawn mower can sputter fuel when a lot of grass builds up on the deck. Mostly, it happens when you mow a wet lawn.

• If your mower has a side discharge system for the grass, like the one Ferris ISX 3300 has, caking of grass clogs the exit and the mower will leave clumps of grass, instead of even cutting patterns.

• Few mowers have a bagger discharge system like the Cub Cadet XT1 series, the Ultima ZT1 50 lawn tractor. These baggers have an upper limit for grass and when this limit is exceeded due to clogged baggers, the lawn mower sputters grass.

• If you have a mulching expert like the Husqvarna MZ54 mower, caked grass deposits above the blades. This results in very poor quality of cutting and can also cause steering issues on the mower.
• Disconnect the spark plug, turn the engine off and Inspect the bottom side of your mower.
• Now, take a basic scraper and scrape off the excessive caked grass from the deck.

Most of the solutions mentioned above can be included in the regular maintenance regime of your mower, like keeping the mower deck clean, cleaning the filters, preventing moisture from getting into the tank and changing fuel regularly. These tips will certainly help your lawn mower from sputtering and backfiring.

Frequently Asked Questions

Q1. Why does my lawn mower sound like it’s chugging ?

Answer – If your lawn mower makes chugging sounds, the fuel supply is blocked. Check the fuel lines to fix this issue. Other reasons can be clogged filters and carburetors, a bad spark plug or old fuel.

Q2. Why is my lawn mower engine not running smoothly?

Answer – Dirty and clogged filters, old fuel and a clogged carburetor is the most common reason for an engine’s rough performance. Clean the filters, the carburetor and change the fuel.

Q3. Why does my lawn mower sound like it’s revving?

Answer – The lawn mower starves for fuel when the airflow to the engine is blocked. It happens due to clogged air filters and blocked fuel lines. It can also happen if the vents of the fuel cap are clogged. It stops the exchange of air with the fuel tank and the ratio of fuel-to-air mix is imbalanced. That is when the carburetor starts running rich, burns more engine oil and the engine starts smoking and revving.

Q4. Why does my lawn mower sound like a helicopter?

Answer – Most of the time, you can identify with the sounds a lawn mower makes but if your lawn mower starts sounding like a helicopter, there is an issue with the blades. The blades might be incorrectly installed or broken. That is why they make this sound while the grass is cut. Hence, check the blades, change the broken blades and install them correctly.

Q5. Why does the engine of my mower sound like a propeller?

Answer – The engine sounds like a propeller when the bearings of the wheels have fallen out. Check the wheels, remove all the debris and replace the misplaced bearings.

Conclusion

There is no dearth of issues that occur on a lawn mower, as it can happen to any machine and it’s very easy to identify when a lawn mower sputters fuel.

As you have learnt above, most of the causes of sputtering on a mower can be avoided with simple maintenance practices.

To prevent your mower from sputtering, you must clean the filters and the mower deck regularly, after each mowing session. If debris settles on them like forever, the repercussions can be seriously damaging.

Plus, never compromise on the quality of fuel and always choose a premium and non-ethanol gasoline for the mower’s engine. Replace the spark plug if it’s faulty and change the fuel cap if it sputters fuel.

With all these tips, I am sure, you will be able to fix your mower if it sputters fuel and will also be able to avoid it in future.

Lawn Mower Engine Surging – Check this easy fix first!

Lawnmower engine surging is a right pain in the Jacksie; it’s an engine that runs erratically and revs up and down by itself uncontrollably. In some cases, it may only happen under certain conditions, for example, only after the mower gets hot or only when the fuel level gets low.

So what causes the lawnmower engines to surge? The most common reason for a surging lawn mower engine is a blockage in the fuel supply, but there are other possibilities:

Often you’ll find playing around with the throttle helps or applying some choke. You are not on your own; this is a regular complaint. In this guide, we will cover the diagnosis, likely causes, and solutions.

Try the easy fix first – replacing/cleaning gapping the spark plug before attempting carburetor work. If your mower engine is a Honda or Kohler, the fix is simple. Honda and Kohler’s surging is commonly caused by a blocked idle jet see “Gas starvation” towards the end of the page.

If you need more help, check out the “How to fix a surging mower video.”

If your surging mower is a Honda, check out the “Honda mower surging video.”

For many mowers, the fix is to replace the carburetor, and as carburetors are inexpensive, it just makes sense to swap it out and save a ton of messing around. You can check out the quality carburetors available and conveniently delivered to your door by Amazon.com.

Need more info on the fuel system, carburetor components, and how they work, you can check them out here.

Briggs Stratton Surging

Surging BS Classic 450, 500, or 550Some engine types are famous for surging; the Briggs Stratton 450, 500, and 550 series engines are fitted with a metal fuel tank and priming bulb-style carburetor. If you have one of these types of engines and it’s surging – You’re in the right place.

If you don’t have this type of carburetor, skip this section and jump to “Surging Test” below. These engines are fitted with a metal fuel tank and carburetor combination. The gasket sandwiched between the tank, and carburetor distorts over time, allowing a vacuum leak.

The vacuum leak causes the surging; replacing the gaskets and cleaning the carburetor/tank will leave it like new, I promise. In this tutorial, we’ll remove the tank/carburetor unit, clean it and replace the gaskets. Just some basic tools are needed, but get yourself a can of carburetor cleaner; it makes the job a lot easier.

In the workshop, I use WD40 carb cleaner, and you can check out all the tools and parts I use here on the “Small engine repair tools” page.

Tools You’ll Need

Here’s a short list of tools you’ll find useful to complete the task of fixing your surging mower. These tools aren’t essential, but they do make the whole job a ton easier; you’ll need:

Fuel treatment – Every small engine owner should use gas treatment. Most people don’t know gas goes off, and gas left in small engines can cause real problems, as you already know.

Using a gas stabilizer will keep the gas in your mower and your gas can fresh for up to two years.

Carburetor gasket – If you’re fixing the BS Classic engine, then you’ll need this gasket set.

Complete carburetor – As an alternative to replacing your BS Classic carburetor gasket, replace the complete carburetor instead; it includes the replacement gasket.

Manifold – This will only be needed if you have confirmed it has failed. Note there are a few different types of manifold pipe, so be sure to check before ordering.

You can check out all these tools on this page “Carburetor Surging Repair Tools.”

This carburetor style is fitted to a few engines and is prone to gasket failure. The job of replacing is simple and will solve the surge. The process is as follows:

Remove the spark plug wire – prevents the mower from starting.

Remove – Remove and clean the air filter and filter housing – Clean it using soapy water, and when dry, smear some engine oil over the surface of the foam. This helps trap dirt.

Remove tank bolts – They hold the fuel tank to the engine.

With fuel tank bolts removed – pull the tank unit straight out gently and remove the governor control link.

Remove the black rubber elbow crankcase breather pipe. Remove the manifold seal and keeper ring. Sometimes they will come loose and get stuck on the manifold pipe.

Remove – Remove carb screws from the carburetor and set aside.

Using a can of carburetor cleaner – clean all the ports on the surface of the fuel tank.

Empty the tank and rinse it out with fresh gas.

Pull the Siphon from the carburetor; they can be stubborn. Remove both gaskets and use carburetor cleaner to clean the siphon metal filter and all ports of the carburetor. Check the primer bulb for damage; mice like to eat them.

Spray – Spray the carburetor with carb cleaner.

Remove – Remove old gaskets and discard them.

Careful of this spring; it lives under the gaskets, and it can drop off and be tricky to find, as I know only too well.

The gasket is a two-part kit; the rubber-type gasket faces the tank. (carb fitted here for demo only)

The Siphon pushes back into the carb with a click. If you don’t hear the click, it’s not right – try again.

Refit the carburetor to the tank. Don’t over-tighten the screws, as this will distort the gasket. Fit manifold seal and keeper. Smear a small amount of oil on the seal; it helps it seat.

Clean the intake manifold. The grey tube in this shot is manifold. Inspect it for any signs of damage; they are prone to cracking. This will also cause a surge.

To fully inspect the pipe, you need to remove the pull assembly.

I would only do this if there was obvious damage to the manifold or if I had replaced the carburetor gasket and the engine was still surging.

This manifold is cracked and will cause a surge.

Before refitting the tank, fit the keeper ring and O-ring seal. Lube the seal before refitting the gas tank.

Offer the carb/tank unit up to the manifold and attach the governor link and spring. Now push the unit firmly onto the manifold. Fit both bolts.

Refit the air filter and spark plug wire. Use only fresh gas; make sure your gas can is clean. Gas older than three months is stale.

If, after fitting the gaskets, you still have a surge – Replace the Manifold.

Surging Test

As you know, gas starvation causes an inconsistent flow of fuel which in turn causes erratic running. And you also know a vacuum leak will cause erratic running, but it is a much less common cause; however, some carburetors are prone to vacuum leaks.

As engine manufacturers strive to make their engines more efficient, they have also made the carburetors more likely to clog; this has become a common issue.

To quickly diagnose which problem you have, a clogged carb or vacuum leak, follow this simple test.

You will need a helper to hold the bail lever or improvise with duct tape. CAUTION careful where you place your fingers and toes; the engine will be running, so the blade will be spinning.

Your mower will have a Manual choke, Auto choke, or a Primer bulb. Identify which type your mower has; the test is slightly different for each.

If you have a manual choke – apply half choke with the engine running.

If the engine now runs without surging – Gas starvation is the likely fault. If it runs just the same – A vacuum leak is a more likely fault.

If you have an Auto choke – Remove the air filter cover and filter – place a clean rag over the intake while the engine is running.

If the engine now runs without surging – Gas starvation is the likely fault.

If the engine runs just the same – A vacuum leak is the more likely fault.

If you have a primer bulb – you can still do the test – while the engine’s running (need a helper); give it some extra gas by pressing the bulb.

If the engine now runs without surging – Gas starvation is the likely fault.

If it runs just the same – A vacuum leak is a more likely fault.

Gas Starvation

If the test revealed gas starvation, it also showed that your problem is likely a dirty fuel jet in the carburetor, or the gas may be stale or contaminated by water.

Cleaning the main jet usually does the job.

Idle Jet Surging – Honda and Kohler use a relatively easy-to-access idle jet that clogs up and causes surging. The Kohler is easier to access than the Honda.

The Kohler is easier to access than the Honda.

Briggs has fitted a plastic carburetor to a range of engines which also clog up and cause surging.

All of these carburetors can be repaired by cleaning, which I’ve covered previously in videos (links below). Videos cover step-by-step removal, cleaning, refitting, and adjusting your carb.

Fixing this is not difficult. Sometimes you can get lucky by just draining and cleaning the gas bowl, which only takes a few minutes.

I have written a complete guide to Carburetor cleaning with pictures; it includes the gas bowl clean-out, which, as said, is worth trying first.

If cleaning doesn’t work out for you, go ahead and swap out the carburetor for a new one. Check out “New lawn mower carburetors page,” here, I’ve listed good quality replacement carburetors for all the most popular engines.

Carburetors aren’t expensive; messing around with them doesn’t make sense.

You might find this page helpful too – “Carburetor repair tools” I’ve listed some really useful tools that make the job easy. Some of these tools I’ll bet you already have some.

But do try cleaning the gas bowl before removing the carburetor.

Finding a Vacuum Leak

Air that enters the combustion chamber without passing through the carburetor is un-metered. This means the fuel-to-air ratio is unbalanced and, in turn, causes erratic engine performance.

When air sneaks in like this, it causes the engine to run lean (lacks gas). A lean engine runs hot, which isn’t good for an engine, especially an air-cooled one.

Vacuum leaks usually occur because of damaged gaskets. Gaskets are sealing materials fitted between the mating surfaces of engine components. Their function is to create an airtight seal.

They are commonly made from paper, felt, cork, Teflon, neoprene, metal, and rubber. The material type is dependent upon where the gasket is to be used.

Gaskets wear out and break down, and that causes surging.

Extreme Caution – You need to be careful, the engine will need to be running, and so the blade will be spinning when running this test.

A vacuum leak check is performed with the engine running and a can of carburetor cleaner; WD40 works, too, (is there anything WD can’t do?)

Spray the cleaner around all carburetor gaskets anywhere the carburetor meets the engine. The trick is to hear an instant change in engine note; that’s the sign of a vacuum leak.

This can be challenging; you must train your ear to notice the instant change in engine note (and not the surging).

Just do a small section at a time; this will allow you to pinpoint the failure area. Jumping the gun and replacing gaskets without finding the actual leak may work out for you or leave you with the same problem after the rebuild.

You’re right in thinking carburetor gaskets usually cause the problem, but other components, such as manifold pipes, can crack or become loose, causing surging.

Fixing A Vacuum Leak

If a leak is detected, replace all carburetor gaskets, and as you have the carburetor removed, go ahead and clean it. Replacement gaskets are available online; you will require the make and model numbers from the engine.

All manufacturers will have a model number printed on a sticker placed on the body or on the engine. Have a poke around; you’ll find it. Most engine manufacturers will stamp the model numbers in an accessible area. Briggs Stratton stamp their numbers on the metal engine cover.

A new carburetor comes with new inlet gaskets; I like to fit original parts where I can; they fit and are guaranteed.

If, after replacing the carburetor gaskets, the engine still surges, you’ll need to go a little further and replace the manifold intake and gasket.

It’s not a big job, and they don’t give a lot of trouble, but they do crack as they get older. I wrote a step-by-step guide showing you everything you need to know – “Briggs Manifold Replacing.”

Related Question

Honda lawn mower surging fix? To fix a surging Honda lawn mower engine, clean the carburetor, gas tank, and fuel filter. Use fresh regular gas or e10. What causes a lawnmower to run slowly? The most likely cause is a throttle linkage bent out of shape by bumping into the shrubbery or a throttle spring has detached itself.

Hey, I’m John, and I’m a Red Seal Qualified Service Technician with over twenty-five years experience.

I’ve worked on all types of mechanical equipment, from cars to grass machinery, and this site is where I share fluff-free hacks, tips, and insider know-how.

And the best part. it’s free!

Riding Lawn Mower Sputtering? Fixes that Work

A faulty lawn mower can change a busy day set aside to mow your lawn into a garage session of fixing the problem. A sputtering sound indicates a mechanical problem with your lawn mower. So, why is your riding lawn mower sputtering?

A riding lawnmower may sputter due to old or contaminated fuel in gas tank, clogged fuel filter, blocked gas cap, faulty spark plug, carburetor issues and dirty air filters. Proper diagnosis can help to identify and fix the exact problem.

Why is my Riding Lawn Mower Sputtering?

Riding lawnmowers from longer storage come with many problems. If you haven’t tuned it up, your riding lawn mower won’t start at all or will sputter. Here are reasons why your lawn mower is sputtering and how to fix them.

Old Fuel in the Gas Tank

Allowing fuel to stay in the gas tank for more than a month can cause problems. It evaporates leaving behind sticky substances that clog the fuel filters, fuel lines, and carburetor components. The clogs prevent the free flow of fuel to cause the sputter.

This is why lawn mower sputtering is common in the spring after a long winter season break. Using cheap fuels that contain a high amount of ethanol can also cause your lawn mower to sputter.

How to Fix

If fuel has stayed in the tank for more than 30 days, discard it and refill the tank with fresh gasoline. When intending to store your lawn mower for a long period of time, be sure to add a fuel stabilizer to the fuel tank. Additionally, use the right type of gas for your lawn mower.

Presence of Moisture in Gas Tank

The presence of water in the gas lawn mower tank, fuel lines, and carburetor will cause problems in the engine. Moisture prevents proper ignition of fuel in the piston chambers and hence causes your lawn mower to sputter.

Water can enter the fuel tank through condensation or after leaving the gas cap loosely secured.

How to Fix

Check if there is water in the lawnmower gas tank. Drain off the contaminated fuel and let the tank dry completely before refilling it with fresh gas. Be sure to clean fuel lines, carburetors, and other components that might be contaminated with water.

Clogged Fuel Filter and Lines

Allowing fuel to stay in the tank for a long period of time will cause fuel filters and lines to clog. Using the same fuel filter for a while can also degrade its performance. The clogs can prevent fuel from reaching the carburetor and piston chambers for combustion.

Clogged fuel filters and lines are characterized by lawn mower sputtering, hard star, and an engine that runs and stops abruptly.

How to Fix

Use carburetor cleaner to unclog the fuel filters and lines. You might need to replace the filters and fuel lines in case they are damaged. Ensure the fuel is fresh and clean before refilling the gas tank.

Clogged Gas Cap Vent

The gas cap contains a tiny valve that allows air into the tank to facilitate the flow of fuel to the carburetor. If this valve is clogged, it will create a vacuum that prevents the free flow of fuels to the carburetor. This problem will cause your lawn mower to sputter.

How to Fix

Inspect the gas cap thoroughly to ensure it’s not clogged. Replace it if leaking or has cracks. Ensure the gas cap is tightly secured on the tank to prevent it from sucking in moisture to the fuel tank.

Faulty Spark Plug

A faulty spark plug can also cause poor engine performance. If a lawn mower is surging, the engine won’t start, or stops abruptly then you need to inspect the spark plug and its components.

The first part is the firing tip where a small metal bend to create a gap between the metal and the electrode. If the metal bend touching the electrode is broken, it will cause the mower to sputter. The second part is the housing which may be cracked.

How to Fix

The spark plug plays a key role in starting the engine. A damaged or loose spark plug can degrade engine performance. Replace the bad spark plug, if damaged or when exhibiting signs of wear and tear.

Clogged or Faulty Carburetor

Using the same lawn mower for a while without cleaning carburetor components can cause it to become filthy. Dust particles from the air and dirty fuel will cause the carburetor to clog over time. Such clogs with cause your lawn mower to sputter or experience a hard start.

Dirty or clogged carburetor components are simple issues you can fix on your own. However, there are other complex carburetor issues that can also cause your lawn mower to sputter. Such issues require professional help.

There are several jets on the carburetor that balances the amount of air that combines with fuel. If the jets are not set properly, they may cause the engine power to degrade.

How to Fix

Dismantle the carburetor carefully to clean and unclog its components. Use a carburetor cleaner to wash the carburetor bowl and other components that may be clogged. If you are not sure how to dismantle a carburetor, you can seek help from a professional.

Dirty Mower Deck

The buildup of dirt and grass in the mower deck may be the reason why your lawn mower is sputtering. It usually happens after cutting grass severally without cleaning the deck or after cutting wet grass in your lawn.

If you are using a side discharge mower, clogged grass in the deck disturbs the exit chambers causing the grass to clump instead of spreading evenly. The unnecessary pressure exerted on the blade will cause the engine to perform poorly.

How to Fix

Tilt your riding lawn mower on one side to expose the deck. Use a wood chisel to get rid of grass and other debris that may be clogging the deck. To prevent the deck from clogging, avoid cutting tall grass when it’s wet. It’s also important to clean your mower thoroughly after cutting grass.

Dirty Air Filter

Staying long without cleaning the air filter will cause the lawn mower to sputter. Dust and other debris from the air can accumulate and clog the air filters. Lawn mower takes in air through air filters which mix with fuel in the carburetor to cause ignition in the combustion chambers.

So, if the air filter is dirty, it will affect the free flow of air to the carburetor. Dirt can also accumulate in the part that leads into the carburetor to cause air obstruction.

How to Fix

A quick solution to this problem is simply to clean the lawn mower air filter with clean soapy water. Air it in the sun to dry completely before returning it to your mower. Replace it if damaged, be sure to choose one that is compatible with your unit.

Final Thoughts

It can be tricky to find out why your riding lawn mower is sputtering. However, some of the insights we have highlighted can help to identify and fix the problem. If the problem persists, it’s advisable to seek help from an expert.

There are few things more frustrating than when you’re trying to mow the grass and the lawn mower keeps dying. Luckily, there are a few causes that you can troubleshoot without having to buy a brand-new mower.

By Melissa Graham | Published May 31, 2023 1:30 PM

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Q: I’ve tried to mow my lawn multiple times this week, but the lawn mower keeps dying. What could be causing it to stop running? Do I need to call a professional or buy a new mower, or is this something I can fix myself?

A: Your mowing shoes are on, you’ve put on sunscreen, and you’re ready to tackle your overgrown yard. But instead of hearing the smooth sound of the engine running, the mower sputters to a stop. When a lawn mower keeps dying, it can prevent a homeowner from doing the necessary work to maintain the home’s curb appeal. The good news is that lawn mower repair can often be a DIY project. From how to clean a lawn mower carburetor to replacing a lawn mower’s battery, the steps below can help solve almost any lawn mower problems.

For those who lack DIY experience and would rather leave the repairs to a professional, one of the best lawn mower repair services will know why a lawn mower won’t start and how to solve the problem so it springs back to life.

A dirty carburetor or clogged carburetor bowl could cause a lawn mower to stop running.

If a lawn mower won’t stay running, a dirty or clogged carburetor could be the culprit. A carburetor mixes the air and fuel in the mower to create internal combustion. If the bowl gets clogged or fuel residue affects the inlet or outlet ports, the motor could stop running. Clogged carburetors also tend to result in the production of black smoke or sneezing and popping noises.

To resolve this problem, it’s possible to disconnect the fuel lines and apply a carburetor cleaner to get rid of any leftover slime from old fuel.

Old gasoline needs to be changed for the lawn mower to run properly.

When a lawn mower sits dormant for months without use, old fuel can evaporate and leave a sticky residue that prevents the mower from running properly. Old gasoline will also have a sour smell. If the lawn mower starts and then dies frequently, it may be necessary to drain the old fuel out of the tank and clean off carburetor ports before adding new fuel. This is especially true for mowers in cold climates, when conditions can lead to condensation inside the fuel tank.

Dirty or defective spark plugs can cause a lawn mower to stop working.

A spark plug ignites the fuel in the lawn mower’s engine, which is why a dirty or defective spark plug could be the reason a mower keeps dying. If the engine is turning over quickly but not starting, the lawn mower sounds weak, or it seems harder to pull the rewind on the mower, the spark plugs may be dirty or defective.

It’s first necessary to find and inspect the spark plug, which is typically positioned on the front of the mower. Here, it’s possible to see if the electrode and insulator have accumulated any buildup or become disconnected. If the plug is dirty, it needs to be disconnected and cleaned with a wire brush and specific spark plug cleaner. (Even if the spark plug doesn’t show significant buildup, it’s still wise to clean it.) The spark plug will then need to be reconnected to see if the mower starts and stays running. If the mower continues to die, it may need a new spark plug altogether.

Too much oil in the reservoir can cause lawn mower problems.

Even the best lawn mowers can experience issues if there’s too much oil in the reservoir. Excess oil in a lawn mower can force the engine to produce more heat, which could lead to the machine overheating. If the lawn mower is blowing white smoke after it’s started, that’s a good indication that there’s too much oil in the reservoir, and a lawn mower that stops running when it’s hot outside could be overheating from an overfull reservoir. Too much oil can also affect the crankcase by causing the oil sump to overflow and causing the crankcase to malfunction.

This issue can be resolved by unscrewing the oil tube and tilting the lawn mower on its side to release the excess oil into a container. At this point, it’s also best to change the oil filter after removing the oil to make sure it’s free from clogs. For those wary of troubleshooting a lawn mower, a lawn mower repair service can check out the machine and help with anything from riding lawn mower repairs to tips on regular maintenance.

A clogged fuel cap vent can make a lawn mower die.

A majority of mowers have a vented fuel cap that helps release pressure in the machine and allows fuel to flow from the gas tank to the carburetor. If the fuel cap vent becomes blocked or clogged, it could lead to excess gas fumes inside the mower, which stops the flow of fuel and could be why the lawn mower keeps dying. A needle or pin can be used to poke out any blockages from the breather hole. If the cap has any damage, it’s likely easier to buy a new cap altogether.

A professional repair service can solve any type of lawn mower problem.

When all of the options have been exhausted and you’re tired of tinkering with the mower, it may be time to throw in the towel and call a professional. The best lawn mower repair professionals have the skills and experience to identify problems right away and can often fix them on the spot so homeowners don’t have to keep running to the hardware store. The mower may also be experiencing an issue that only a professional can address, which is especially true if there is black smoke coming from the mower or if the mower starts vibrating or shaking once started.

Lawn mower maintenance can keep the mower running smoothly.

As with any appliance or machine, regular maintenance ensures a mower is in mint condition and won’t experience the many problems that can come with neglect. Regularly cleaning debris from air filters and mowing decks, removing any old gas from the tank, and replacing the battery when needed are all good practices to keep in place when it comes to lawn mower maintenance. The more a mower is taken care of, the less likely a homeowner is to experience issues such as a stalling lawn mower or lawn mower chugging.

Why is My Lawn Mower Smoking?

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Leaking oil from the exhaust is the usual cause of blue, white or black smoke from a lawn mower. Learn to assess and fix a sputtering, smoking lawn mower.

Gas-powered lawn mowers can be full of surprises. Perhaps the most startling one happens when you pull the mower cord and the engine sputters into action, only to be followed by clouds of smoke from the motor and under the mower deck. What’s going on and what should you do about it?

Why is My Lawn Mower Smoking?

There are several reasons your lawn mower could be bellowing out smoke. While it looks kind of intimidating, like something bad is about to happen, in most cases, it’s nothing to be worried about, and it’s not usually hard to fix.

Oil spilled onto the engine: If you changed your lawn mower’s oil recently or added more to the oil reservoir, some may have spilled out onto the engine. Mowing on a steep slope in the yard, or turning it over to adjust the blade, could also cause some oil onto the engine. When that happens, the oil will burn off, causing blue or white smoke. It’s best just to let it burn off, so when you start up again, the oil will be gone.

Overfilled oil reservoir: Too much oil in the reservoir can also cause a lawn mower to smoke. The lubrication systems in most mowers are not well sealed, and usually there’s an overflow oil reservoir with a relief outlet where excess oil can leak. Check the oil level in your mower, and if there’s too much in there, consult the manual for how to drain some out until it’s back at the proper level.

Mower burning too much gasoline: The carburetor regulates the ratio of gasoline and air in a lawn mower engine. If the carburetor isn’t getting enough air, that means the mix is heavy on gasoline, which can cause black smoke from the exhaust. Often times that’s caused by a dirty air filter, which is preventing enough air from getting to the carburetor.

Different Types and Colors of Smoke

If the smoke is black, there may be an engine problem behind the smoke. In such cases, your first step after the mower cools down should be to check the air filter. If it’s clogged, the combustion chamber may not be getting enough oxygen, resulting in a too-rich fuel mixture that will cause the engine to run poorly and even spew smoke. The solution is to change the air filter, a relatively easy task.

Blue and white smoke is the result of oil on the engine. If there’s too much oil in your oil reservoir, you may want to drain some of it out. If it’s just some oil spilled onto the engine, all you have to do is let it burn off.

When to Take a Smoking Lawn Mower to the Repair Shop

If your smoke problems persist, chances are the oil seals in the engine lubrication system or around the pistons are the issue, or you may even have a cracked crankcase. These are repair jobs for a small engine pro, unless you’ve got experience working on engines.

There is also a chance the smoke is simply the result of a carburetor that needs cleaning or adjusting. If you’re up for it, most owners’ manuals include instructions on how to adjust and clean the carburetor.

Remember, it’s important to tune up your lawn mower at the start of the season, which will help make sure it’s running properly and prevent potential problems like a Cloud of smoke following you around the yard.

Troubleshooting and Fixing the Mower

Mark Johanson is an experienced home and garden writer/editor/publisher. He has written several books and hundreds of magazine articles. He has edited and directed more than 400 DIY and gardening books, including the BLACKDECKER® Home Improvement Library series and two of the best-selling gardening books in North America. He is an experienced DIYer and enthusiastic gardener.