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Reasons Lawn Mowers Won’t Start When Hot

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Does your lawn mower start and run fine when it’s cold, but performance dips when it gets hot? Or worse, the engine stalls? It can be frustrating since we use lawn mowers when the sun is out. As someone who has had to deal with this personally, I did a lot of research to figure out the causes and how to fix them.

The most common reason is a faulty spark plug. But it could also be due to an overheating engine, clogged carburetor or damaged coil.

Faulty Spark Plug

I will start with the most likely cause: a defective spark plug. If your lawn mower has trouble starting or stalls when it is hot, this is the first place to look.

There are many reasons why a spark plug goes bad: soot buildup, worn out, warping, burned out, cracked parts, etc.

Turn off the lawn mower and check the spark plug. If it looks burnt or covered with soot/dirt, replace it. It is possible to clean a spark plug, but you should be replacing it at least once a year. You can use a Flada Spark Plug Tester to determine if it is still working.

Spark plugs are cheap and widely available. Just make sure it is compatible with the lawn mower. Check the manual for the specific type of spark plug it needs. You must get an exact match.

Engine Problems

An overheated engine is one of the most common reasons why lawn mowers stall when it is hot. Intense heat has a negative effect on the engine and eventually it will stall or completely stop.

Lawn mowers have cooling fins which dissipate heat, allowing the engine to run continuously. As you mow, grass clippings, dust and dirt build up around the cooling fins and clog it.

The fins, which are supposed to cool the engine, does the opposite. The grass and dirt block the fins and trap heat inside, causing the temperature to rise. This forces the engine to shut down.

The solution is to clean the fins. Turn the lawn mower off, let the engine cool and remove the casing. Use a brush or clean rag to remove grass, dirt, twigs etc. Put the casing back on.

Turn the lawn mower back on and it will run normally. Clean the cooling fins regularly to avoid dirt buildup.

A Dirty Mower Deck

The deck keeps grass clippings and dirt from flying everywhere, but it does accumulate. If there is too much clogging, the blade will not be able to turn. This forces the engine to work harder to make the blade spin, causing it to overheat.

To test this, pull the starter rope. If it takes more effort than usual to pull (or is stuck), the deck might be stuffed with clippings and debris.

Turn off your lawn mower. After the engine cools, flip it over and inspect the deck. Odds are there will be a lot of debris, grass, twigs and other materials scattered. Use a trowel or similar tool to scrape them off.

I love the outdoors and all the tools for maintaining gardens, yards and lawns. The only thing I am more passionate about is sharing what I know about garden and outdoor equipment.

Riding Lawn Mower Stopped Running While Mowing: (Reasons Fixes)

Did your lawn mower stop running while cutting the grass? There can be several possible reasons if the lawn mower stops running. You can sort out the reasons and can fix them. But how to fix riding a lawn mower stopped running while mowing?

Firstly, identify the reasons why riding a lawn mower stopped running while mowing. It may occur due to low oil levels, debris around the air filter/fuel line, and the loose carburetor bolts. Check the oil level, clean the debris, and fasten the carburetor bolts to fix the problem.

Let’s know the in-depth process to troubleshoot the lawn mower that stopped running while mowing. Let’s come to the discussion.

Why Do Lawn Mowers Stop Running While Mowing? Top 3 Reasons

It is a confusing moment when your lawn mower runs fine but suddenly stops running with no warning. It mostly happens when the lawnmower overheats. Your lawn mower can be overheated because of any of the below-listed reasons:

Low oil level-

Lawn mowers also use engine oil like other big vehicles to protect them from overheating. Maybe your lawn mower engine oil level is low, which may cause overheating of the engine.

Grass or debris-

Grass or twigs particles and other debris can also cause blockage of air from reaching the engine. Debris in the engine shroud, side panels, or cooling fans can prevent air circulation that may overheat the engine.

Loose fasteners-

A lawn mower may also stop running when there is a problem with the carburetor bolts. Carburetor mounting bolts can cause blockage of air, which may overheat the engine.

How To Troubleshoot Riding Lawn Mower Stopped Running While Mowing?

Here we will guide you about troubleshooting a lawn mower that won’t start after hitting something and below fixing the lawn mower issues that stopped running while mowing.

Things you will need:

You should have the following essential tools and equipment to troubleshoot and fix the issue successfully. This list includes all the tools required for troubleshooting and fixing the above three issues.

You can use any of the available Gas for cleaning auto parts. But we recommend GARAGE BOSS GB310 Briggs and Stratton. It is best for cleaning all vehicle engines and other parts, from small engine vehicles to large trucks.

Solution 1 (Troubleshoot Low Oil Levels):

First, check the lawn mower oil level; maybe the oil level is low. Follow below simple steps to check the oil level.

The Easy 2-step Solution to Troubleshoot Low Oil Levels:

Step 1- Park your lawn mower on a flat surface

First, park your riding lawn mower on the flat surface. It is essential to be on a flat surface to check the right level of oil. Leave it for a few minutes to balance the oil level.

Step 2- Check the Oil Level

Now unscrew the dipstick and remove the dipstick from the oil tank. Do not check the oil level because the whole dipstick will be covered with oil.

Clean the dipstick with a clean cloth and insert it back into the tank.

Now take it out and check the oil level. You will see two holes on the dipstick bottom. If you see the oil level is between these two holes, it is okay. But if it is lower than the last hole, the oil level is low.

Briggs And Stratton Overheating Engine Valves

If the level is low, refill it with fresh oil. Before refilling the oil tank, ensure you have the recommended oil according to your lawn mower brand.

Solution 2 (Remove debris or grass particles)

You have checked the oil level is fine, okay, now you should check for debris or grass particles. After removing the debris or grass, you may be able to fix the lawn mower issue.

The Easy 4-step Solution to Follow to Remove Debris or Grass Particles

Step 1- Shut off the fuel valve

First, go ahead and shut off the fuel valve for safety. It will protect from leakage issues.

When you go ahead, see the junk around the motor, air filter, and other parts.

Step 2- Take gas in the tray

The next thing to do is to take the tray and put the little gas in the tray.

Step 3- Stroke with a brush

Now dip the brush in the gas and stroke it around the lawn mower’s parts. Try to move it forth and back for proper cleaning and removal of debris. It will also remove the dry grass particles.

Try to cover all small areas and ensure you have covered all the exposed parts, such as fuel lines or air filters. It is good to cover all the areas twice.

Once cleaned, take the rag and use it over the surface to clean the gas chemical.

Step 4- Clean the grass under the base

Now turn the lawn mower on one side to clean the grass particles under the base area. These particles also slow down the riding lawn mower if poorly stuck.

Once you have tilted the lawn mower, clean the under-base carriage. Cover the inner base where lawn mower blades, belts, and other parts are. It will remove the clogged grass.

Also, clean the sidewalls. You can use a screwdriver or chisel for easy cleaning of sidewalls.

Do it carefully, do not do this with bare hands because blades are so sharp that you may cut your hands. So wear safety gloves. Once you have done it, turn back the lawnmower side and test it.

Solution 3 (Fix loose fasteners)

Your lawn mower debris is cleaned, and the oil level is also okay, but still, it has the problem. You should check the carburetor bolts. If they are loose, fasten them to remove the problem.

Easy 2 Step-by-Step Solutions to Fix Loose Fasteners

Step 1- locate the Carburetor bolt

First, access to the carburetor of your lawn mower; it is located near the air filter. Check their bolts; if you see they are loose, you should fasten them.

Step 2- Fasten the bolt with the wrench

Are bolts loose? Take the wrench according to the carburetor bolt size. Fasten the bolts and make sure they are properly tightened. If you face some problem holding the bolt, you can also use another wrench to hold the bolt in place.

Once you have fastened the bolts, test the lawnmower to ensure the removal of the problem. I hope your problem will be solved.

But if you see the problem still exists, call for a professional service to fix the issue.

Frequently Asked Questions(FAQs):

How many fixings did the riding lawn mower stopped running while mowing

Generally, lawn mower fixing when stopped running while mowing can cost between 50 to 90 dollars. It includes the cost of gas, gloves, wrenches, and other accessories.But if you already have gloves and wrenches, it will not cost you more than 25 dollars. The professional guy may charge you between 150 and 200 dollars if you provide professional services.

Why would my riding lawn mower stop without warning?

The sudden stoppage can be because of engine overheating. Sometimes it also shuts down when you mow large grass that is badly stuck between blades or belts.

What should I do when the lawn mower stops running while mowing?

Allow your lawn mower to cool, and try it after 30 minutes. Check the air filter, carburetor bolts, spark plug, and debris if it does not start.

Can I clean the Carburetor debris without removing it?

Yes, you can use a carburetor cleaner to clean the carburetor and air filter. You can clean the outside and inside surface of the carburetor with a carburetor cleaner.

Final Verdict

A lawn mower is a straightforward machine that can be fixed easily. For most of its problems, you do not need to take professional services.

If your riding lawn mower stopped running after some time while mowing, find out the possible reason and fix it. It will not be just cost-effective but also train you for future issues troubleshooting.


Riding Lawn Mower Won’t Start After Running (How to Fix?)

If you have a large lawn to cut, owning a good sit-on mower is more than just a pleasant luxury, it’s a necessity. Beyond a certain size of lawn, it is no longer feasible to mow with a traditional push mower, but a sit-on version will let you finish the job in no time.

However, sit-on mowers – like other types of mower and just about any kind of power tool – can develop problems, and one is that it starts up fine at first but then won’t start up again after being used. Here, we will look at the question of what to do if a riding lawn mower won’t start after running.

The basic tenet of repair work

Before we start, let’s just remind ourselves of the proper procedure to follow when trying to repair any kind of machinery.

If you want to repair something, first, you need to identify the problem. To do this, you need to narrow down the search area to determine where the problem lies. By systematically eliminating all possibilities, you can locate the problem – and once you find it, you can fix it.

First question

In order to work out where the problem lies, you need to ask yourself some questions. The first question – a very obvious one – is why the lawn mower stopped in the first place. Did you stop it, or did it stop by itself?

This is a very important question to ask since it will help you determine where to start looking for the problem. If the mower won’t restart after stopping by itself, the fact it was running might not be relevant.

By this, we mean the fact that it won’t start after running might be coincidental – that it was running before might not be related to why it won’t start now, and the problem might lie elsewhere.

To begin with, we will look at why your mower won’t start if you stopped it yourself – because in this case, the problem is probably to do with the fact that it is hot and not something else.

Why it won’t start after running if you stopped it yourself

Problems with restarting a mower that has been shut off after running are almost always related to compression, i.e. the engine’s ability to build pressure on the cylinder.

Basically, when an engine runs, it heats up – and metals change size and shape when they are hot. The change is almost imperceptible, but even this tiny amount of difference can cause a problem.

Since the valve changes size, it may no longer be able to close 100% and so you won’t have the necessary pressure required to start the engine.

To see if this is the case, test the compression when cold and test the compression when hot. If you have more compression when cold, this is an indication that you have identified the problem. To rectify it, ensure that the valve lash is set correctly when cold.

The problem with this is that it is not an easy job either to test this or to fix it by yourself unless you know your way around engines. If you are not sure what you are doing, you might be better off asking a professional to check for you.

Another possibility is simply that the engine is overheating. This could happen if grass clippings clog the cooling fans. This is something that is easier to check, so you should eliminate this before calling in a mechanic.

Here’s a video of someone dealing with a similar problem.

What about if you lose power during mowing?

If your mower shuts off while you are mowing and won’t restart, you might suspect that it is a heat-related problem, but it could also be something else. Here are some other possibilities that you should try to eliminate.

Are you out of fuel?

So we’re starting with the most obvious, but in the interests of being systematic, check it.

Having problems restarting after running out of fuel and refilling?

Perhaps your mower stopped because it was out of fuel but after you refill it, it still won’t start. This is probably not a heat-related problem at all. Here, it is more likely that there was some debris floating in the fuel and was sucked into the fuel line when the fuel ran out.

To rectify this problem, ensure that the fuel lines are clean and free of debris. After removing any debris, it should start again.

Cutting tall grass or build-up of grass under the mower

It is possible that the grass you are cutting is too long and is clogging up the mower, causing the engine to stop. Try clearing out the cuttings and then adjusting the cutting height.

Similarly, if the mower becomes too clogged up by grass cuttings, the same may occur. Try clearing it out and trying again.

Old or dirty spark plugs

This is another obvious one to check. If your spark plugs are old or dirty, replace them. This will probably increase your mower’s performance instantly.

This is the kind of problem that might make you think the problem is because the mower has been running when actually the problem lies elsewhere. Make sure your spark plugs are in good condition, clean and properly connected to eliminate this possibility.

Dirty air filter

As with the spark plugs, this is the kind of problem that can make you think the problem is heat-related when it isn’t. If your mower loses power and then won’t restart, it might be due to dirty air filters.

This is a simple problem to check and fix. Make sure the filters are clean and in good working order and try again. If this was the problem, it should start up again easily.

Eliminate all possibilities to find the problem

If you have a problem restarting your mower after it has been running, the first thing to do is to eliminate all the simple issues.

If none of the more obvious problems are to blame, you could well have a problem with compression due to a valve. If this is the case, unless you are very confident around engines, you might need to think about calling a professional.

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.

Problem Symptoms
Dirty carburetor Engine won’t start, sneezing or popping sounds, black smoke, leaking fuel
Old or bad gasoline Rough idling or stalling, pinging sound, gas smells sour
Dirty spark plug Harder tugging on rewind required, gas running out quickly, engine turning over but not starting
Excess oil White smoke, overheating engine, slow starts
Clogged fuel cap vent Engine sputtering or misfiring

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.

Why did he kill this grass!?

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.