Mower does not start. Lawn Mower Won’t Start (Why How to Fix)

Lawn Mower Won’t Start (Why How to Fix)

A lawn mower that won’t start can be baffling, especially if you don’t know much about engines. Most people learned the workings of the combustion engine in high school during science class. Vague memories of Nicolaus Otto’s 1876 early engines certainly won’t help get your lawn mower up and running again. So, instead of digging out an old high school textbook to find a solution, let me share with you the most common reasons why your lawn mower’s engine won’t start.

Why Your Lawn Mower is Not Starting (The Short Answer)

The most common causes for a lawn mower not starting usually stem from problems with the starter system (the battery), the fuel delivery system (the fuel pump), the air intake, and the ignition spark (the air filter and spark plug). A dirty carburetor or safety system can also prevent a mower from starting.

Possible Reasons Why Your Lawn Mower Won’t Start

I’m pretty sure that by the time you get to the bottom of my list, you will have found the reason why your lawn mower isn’t starting. So, let’s take a look at the possible causes.

Dead Battery

The first place to start is at the battery. Riding mowers, zero turns, and a few walk-behind lawn mowers use a starter motor and a battery to fire up the engine.

If your battery isn’t fully charged or is dead (I wrote about symptoms of a bad/dead lawn mower battery here), then the starter motor won’t be able to crank over the engine.

If you have a battery tester, you can check the volts of the battery and the cold cranking amps. Alternatively, you can have the battery tested at an auto parts store.

Bad Spark Plug

Old or damaged spark plugs cannot provide a spark inside the cylinder required to ignite the fuel vapor from the carburetor. No matter how many times you try to start the engine, if the plug is bad, the engine just isn’t going to start.

How do you tell if a spark plug is bad? You test it. When I need to test a spark plug, I like to use an inline spark plug tester. This is a little device that can be fitted in seconds and sits between the spark plug and the ignition cable. With the tester installed, you just need to crank the engine with either the key or pull cord and check to see if the tester lights up.

Alternatively, you can remove the spark plug and crank the engine. As long as the spark plug is connected to the ignition cable and touches a metal part of the mower, you’ll see a spark when you crank the engine if the plug is good.

Blocked Air Filter

The air filter is the one defense the engine has to stop any debris from entering the engine when it draws air into the carburetor. This specifically designed filter allows a certain amount of air into the engine during operation.

Once the air filter becomes blocked or dirty, the air getting into the engine is decreased, resulting in the engine not starting, poor performance, and stalling.

To check the air filter, you’ll need to pop off the air filter housing cover and remove the filter. Once the filter is removed, you can check it to see how blocked or dirty it is.

Blocked Fuel Filter

Like the air filter, the fuel filter is a protective measure the engine uses to stop dirt from entering the engine. Rather than filtering air, this filter removes any debris and impurities from the fuel.

Lawnmower Only Starts With Starting Fluid! Step By Step Repair!

Once the filter becomes clogged, it no longer allows fuel to flow through the fuel system, and the engine becomes starved. An engine that is starved by a clogged fuel filter is not going to start.

You’ll find the fuel filter located between the fuel tank and the fuel pump. Usually, these are small see-through devices that you can inspect visually.

Once you find the filter, you’ll want to see if it’s dirty. If it looks like it has a bit of debris or has turned black, then you’ll know you need to replace your fuel filter as it’s probably stopping your engine from starting.

Broken Fuel Pump

The fuel pump is the device that transfers the fuel from the fuel tank to the carburetor. Mower fuel pumps rely on a diaphragm, spring, and a vacuum from the engine.

It’s common for debris to enter the fuel pump and clog it up. If a lawn mower fuel pump is not working properly, it will starve the engine of fuel and result in your mower not being able to start.

A quick way to test a lawn mower’s fuel pump is to remove the outflow pipe from the pump and crank the engine. Once you crank over the engine, fuel will spurt from the fuel pump. If it’s broken, then no fuel will come out, and you will have pinpointed your problem.

Blocked Fuel Cap

You would think that such a simple thing as a fuel cap can’t stop a mower from starting, but it really can.

You’ll notice that on the top of a mower’s fuel cap, there is a tiny hole. This hole allows air to enter and exit the fuel tank. If your lawn mower’s gas cap is not venting (i.e. this hole becomes blocked), a vacuum can build in the fuel tank, preventing gasoline from flowing through the fuel system.

So pop off the fuel cap and take a look at the hole. If you find that it is blocked, more than likely from yard dirt, then it’s probably the reason why your mower is not starting.

Dirty Carburetor

If you have checked off all the other items on this list, then your mower’s problem likely comes down to an issue with the carburetor.

The carburetor has a small jet inside which vaporizes fuel so that it can be ignited in the cylinder head. Contrary to popular belief, liquid gasoline doesn’t burn; it’s the fumes from gas that do.

So, if this tiny jet becomes blocked, which is common if bad fuel or junk gets into the carburetor, it can no longer create the vapor needed to start the engine. The only way to check for a dirty jet is to remove the carburetor and inspect its interior.

Safety System

Finally, one part of the mower that gets overlooked is the safety features designed to stop the mower from starting. This isn’t a result of a malfunction but a feature that keeps you out of danger.

The seat, the brake, the blade engagement button (these apply to riding mowers), and even the bail lever are all systems that stop the engine from starting.

So, if you’re unsure of your mower’s correct starting procedure, grab the manual or look online at the manufacturer’s website for the proper method.

Electrical Lawn Mowers

It’s not only gas-powered lawn mowers that have problems starting; electric mowers, both battery and corded, can suffer from their own specific issues. Here are a few common problems that can stop your electric mower from starting.

Damaged Cord

Corded electric mowers have a long cable connecting the mower to the power outlet. These cables can take a real beating when dragged around the yard.

The easiest way to check the cable is to inspect it visually. Alternatively, you can use a multimeter to test the voltage coming out of the cable once it’s powered up.

Poor Electrical Connections

The connection on an electric lawn mower often suffers from some corrosion. This is usually due to the damp conditions the mower spends a lot of its time in.

The connection may be located where the battery/cord connects to the mower or, more commonly, where the cable connects to the electric motor.

By removing the mower’s cover, you’ll expose the electric motor. Here you’ll be able to see if the terminals are corroded and causing a problem with the lawn mower starting. Alternatively, you can use a multimeter to test the connections.

Worn Out Brushes

Electric motors require power to be transferred from the terminals/stator outside to the spinning rotor inside. To do this transfer, electric lawn mower motors use spring-loaded brushes that rub against the spinning internal rotor.

With the friction of the spinning, the brushes wear down and need to be replaced. This is really the only servicing an electric lawn mower requires.

Once you have access to the motor, you should be able to pop out the brushes by removing the terminal mounting screw. With some motors, you don’t even need to do this since the brushes are just clipped in for easy removal.

Once you have the brushes removed, you can inspect them to see if there is enough length left to make contact with the rotor. They are usually marked, showing when they need to be replaced.

How to Fix a Lawn Mower That Won’t Start

So, was I right–did you find the reason why your lawn mower won’t start? Now let me explain how you can get it fixed.

Charging the Mower’s Battery

Charging your lawn mower’s battery can be done in a few different ways. If you have an old charger, then you’ll need to disconnect the cable from the lawn mower. You can leave the battery connected if you have a modern Smart controlled charger.

To disconnect the battery, a small wrench set will do just fine. Just remember that you disconnect negative, then positive, and then connect, positive then negative.

Next, you’ll need to set your charger setting. This tells the charger the battery’s voltage and specification, such as lead acid.

Both types of chargers will tell you when the battery is charged, but not all chargers will switch off. So, make sure you know how your charger works before you use it.

How long does it take to charge a lawn mower battery? That will depend on the type of battery you have, the battery’s voltage, and the charger you’re using.

Tools Required to Charge Your Lawn Mower’s Battery

Replacing the Spark Plug

To replace the spark plug on your lawn mower, you’ll first need to remove the ignition cable attached to the existing spark plug.

Next, use your plug wrench to remove the existing spark plug and set it to one side. Now insert the new spark plug into the lawn mower.

There should be no reason to test the gap on your new spark plug, as it should have already been gapped correctly.

Next, with the new spark plug loosely threaded back into the engine, use your plug wrench to tighten the new spark plug snuggly. Finally, reattach the ignition cable, and you are done.

Tools Parts to Replace the Spark Plug

Replacing the Air Filter

Unclip and remove the air filter cover the same way you did when inspecting it, and set it to one side. Next, remove the old filter/s and discard them in the trash.

Now use a cloth to give the inside a good wipe down. If it has some old oil and gasoline residue, then you can use a little WD-40 to help remove the grime. Then check your new filter/s and see if they need to be oiled.

Specific oil helps keep the filter supple and stops them from drying out and cracking. However, oil shouldn’t be used on paper filters, only on sponge filters. If your filter/s does need to be oiled, then you can use a can of spray filter oil to complete this stage.

With the air filters prepped, you can go ahead and insert them into the lawn mower’s filter housing. Finally, reattach the filter housing cover, and the fix is complete.

Tools Parts to Change the Lawn Mower’s Air Filters

Replacing the Fuel Filter

Installing a new lawn mower fuel filter isn’t difficult. First, you’ll want to switch off the fuel using the fuel cut-off valve. This is to stop the fuel from flowing out once the filter is removed.

Next, grab yourself a pair of pliers and remove the spring clips holding the fuel lines to the fuel filter. You just need to slide them down the fuel line, so they no longer rest on the filter.

Then twist the filter while holding the fuel lines. This helps loosen the lines from the filter. Once the filter no longer grips the fuel lines, you can go ahead and pull off both fuel lines. Just be careful as a small amount of fuel will come out of the filter and line.

Next, reattach both fuel lines to your new fuel filter. You’ll notice an arrow on the side of the filter stating the direction the fuel flows in, so make sure to install the filter in the correct fuel flow direction.

Then use your pliers to reposition the spring clips so that they sit over the lines and the filter and grip everything in place.

Finally, switch the fuel back on to test the mower. It will take an extra few pulls to get fuel back through the system and fill the new filter.

Tools Parts to Change the Lawn Mower’s Fuel Filters

Installing a New Fuel Pump on a Riding Mower

Lawn mower fuel pumps vary as there are a number of different designs, but the principle is the same. So, here I want to talk you through a standard fuel pump that is connected to an OHV, which most riding mowers and zero turns have.

First, turn off the fuel cut-off valve to prevent fuel from leaking from the fuel lines once you remove them. So, locate the fuel pump and remove the spring clips from the three pipes. To do this, use a pair of pliers and slide the clips down the pipes.

Next, slide off the three pipes from the fuel pump. So that you don’t confuse which pipe is which, use a marker pen and number them 1, 2, 3, then do the same on the old pump.

Then you want to use your socket wrench to remove the two bolts that hold the pump to the mower. Once the bolts are removed, you can go ahead and remove the old pump.

Position the new pump on the lawn mower and insert the bolts you previously removed. Use your socket wrench and tighten up the bolt nice and snug, but not too tightly as these pumps are usually made of plastic and can crack.

Once the new pump is mounted, attach the three pipes using your marked numbers as a reference and slide the spring clips back into the correct position. If you look closely at the pipes, you should see some indent from their original position.

After completing this step, you can switch the fuel back on and start the mower. A few extra cranks will be needed to get the fuel back through the system.

Tools Parts to Change the Lawn Mower’s Fuel Pump

Unclogging the Fuel Cap

To unclog a fuel cap, you just need to poke the hole with a pin or needle, whichever you have at hand. Use whichever tool you select, push it through the hole, and dislodge the dirt. There probably isn’t going to be much, just enough to cause a problem

Tools Parts to Unclog a Fuel Cap

Replacing the Carburetor

Cleaning a carburetor is a task that not everybody will want to undertake. But if you’re up for the task, I’ll cover how you can swap your old one for a new one. Depending on the particular engine, replacement carburetors start at about 30.

Lawn Mower Won’t Start. How to fix it in minutes, for free.

Removing the Lawn Mower’s Old Carburetor

First, remove the air filter cover and filter and set them to one slide. Then, use your socket wrench to remove the couple of bolts holding the back plate of the air filter housing to the mower. These bolts also pass through the carburetor and hold it in place, so once the bolts are removed, the carburetor will be loose.

Next, switch off the fuel using the fuel cut-off valve. Then, use your pliers to remove the spring clip holding the fuel line onto the carburetor. With the clip removed, you can pull off the fuel line.

Next, you’ll need to remove the governor/throttle linkage from the carburetor. To do this, twist them out of the brackets with a bit of persuasion. This was the last thing holding the carburetor to the mower, so now that it’s fully disconnected, you can set it to one side.

Install the Lawn Mower’s New Carburetor

Now it’s on to installing the new carb. Hopefully, the new carburetor came with two new gaskets– one that sits between the carburetor and the engine and another between the carburetor and the air filter back plate. If it didn’t, you need to salvage the old ones as long as they are still in good condition. If they are worn or damaged, you’ll have to get replacements.

So, you’ll need to first attach the governor/ throttle linkage to the new carburetor. Then, attach the fuel line and position the spring clip. Now thread your bolts through the air filter back plate, the gasket, the new carburetor, the second gasket, and finally into the engine. Repeat this with both bolts and make sure to get everything in the correct order.

The last job is to tighten the bolts and reinstall the air filter and cover. That’s it – see, it’s not too difficult. With the new carburetor installed, you can switch the fuel back on and crank the engine.

Tools Parts to Replace a Carburetor

Electric Mower Fixes

That’s the gasoline powered mower out the way. Now we can move on to the electric mowers. If your electric lawn mower doesn’t start, let’s see if these fixes can get it working again.

Replacing the Cord

Replacing the cord on an electric mower is as simple as it sounds. There’s not much you can do with a damaged cord. You could try to repair it, but this will mean you have to cut a section out, and the cable will get shorter. So, I recommend replacing it with a new one.

Cleaning the Connections

First, remove the connectors from the terminal. Then take some sandpaper and run it over the corroded surface. Once you have removed most of the corrosion, spray the metal area with some contact cleaner. Give the cleaner a minute to soak in, then brush it with an old toothbrush.

Next, use a cloth to wipe down the area you have been working on. Once you are happy with the outcome, repeat the process to include the connector and the terminal. When complete, you can reattach the connector to the terminal. If you find the connector is a little loose, try to give it a little pinch with a pair of pliers.

Finally, make sure everything is connected correctly and that everything is dry.

Tools Parts to Clean Electrical Contacts

Changing the Brushes

The last item on my list is changing out the bushes on your electric motor. While most electric mowers allow you to change brushes, some don’t. So, if your lawn mower gives you the option to change them, then this is what you’ll need to do.

First, remove the mower’s cover and expose the top of the motor. A screwdriver should be enough to remove the top. Then you’ll need to remove the old brushes. If you have ones that are just clipped in, you can unclip them, slide out the old ones, and slide in the new ones. For the rest of you with replaceable brushes, you’ll need to remove the terminals.

Use your screwdriver to remove the screw holding the terminal in place. Once this is removed, you should be able to slide out the old brush and slide in the new one. You need to repeat this for both the positive and negative terminals. With the new brushes installed, reattach the terminals and replace the cover.

Tools Parts to Replace Motor Brushes

About Tom Greene

I’ve always had a keen interest in lawn care as long as I can remember. Friends used to call me the lawn mower guru (hence the site name), but I’m anything but. I just enjoy cutting my lawn and spending time outdoors. I also love the well-deserved doughnuts and coffee afterward!

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My mower won’t start

Starting problems with your lawn mower fall into 2 basic causes: fuel problems and ignition problems. The following is a simple checklist you can follow to help isolate a possible cause. This is not an exhaustive guide and certainly not a repair manual. However, there a few steps you can take before taking it to the repair shop for a thorough fix.


This is the first and most obvious thing to check, especially if you weren’t having startup problems last year. Be sure that the machine has an ample supply of fresh fuel. It’s amazing how often people will get their mower out of cold storage the first warm day in spring and find their mower just won’t start. Forgetting that they left the fuel in the tank from the previous year. Today’s fuels don’t age well. In fact today’s gasoline is much like milk and starts to go bad quickly, often in as short a period as 60 days.


Make sure that the ignition switch is on, that all attachments are disengaged and that the transmission is in neutral. Most machines have safety mechanisms that will not allow them to start otherwise. Consult your owner’s manual for the starting procedure for your machine.

Make sure the spark plug wire is firmly attached to the spark plug.

If it still doesn’t start, check for a spark by removing the spark plug and grounding the hex part of the spark plug to a bare metal part of the engine. Remove any spilled gasoline that is nearby first, then spin the engine by pulling the rope or turning the key. You should see a blue spark jump across the plug gap. If you have a good hot spark, skip to the carburetor section.

lf the spark is yellow and weak, or there is no spark then the first thing to do is try a new spark plug. Don’t try cleaning the old one. Set the new plug gap to the proper spec (usually 0.030) and check for spark again. If you do see a spark, install the new plug and try to start the machine.

If there’s still no spark, try cleaning and setting the points on older machines, or replacing the electronic ignition module on newer machines. Before replacing the old module test it by disconnecting all the wires from the module terminal that connect to the kill switches and recheck for spark, if you do see a spark then a wire or switch is probably defective. Also check the flywheel key. That affects the spark timing, usually the key will need replacing if you strike something while mowing and the engine stops.

Checking the carburetor and fuel system

If the fuel is fresh, you have a good spark and still won’t start, you must make sure that fresh gasoline is getting to the carburetor. Make sure that the fuel shutoff valve (if present) is opened, and that the fuel line is not plugged or kinked.

Also be sure the fuel cap vent is open and any screens in the tank are clear of debris. If fuel can flow to the carburetor, carefully place 1 teaspoon of gasoline down the spark plug hole (or a add shot of starting fluid into the carburetor throat). Re-tighten the plug and try to start the machine. If it runs for a second or two, then quits, chances are the carburetor needs to be serviced (disassembled and cleaned inspected, then rebuilt) or you have an air leak somewhere.

Make sure all mounting screws or bolts are snug and gaskets are not missing sections. If the carburetor is a bowl-type check for water in the bottom of the bowl (but do not let the float swing all the way down or the float needle will fall out!).

Hopefully, this will give you a little insight in what to look for if your mower won’t start. Most starting problems are fuel related because the previous year’s fuel wasn’t removed. You may have gone years without removing the fuel at the end of the year without having any starting problems. There is a chemical process called varnishing that puts a coating on the inside workings of your fuel system. Over time this process continually worsens until your system becomes inoperable.


Gasoline can ignite very easily. Work only in well-ventilated areas and away from sources of heat, sparks, and flames. Always wear safety glasses, and be careful of sharp blades. Keep a fire extinguisher nearby.

The Ultimate Guide: Troubleshooting Your Lawn Mower When It Won’t Start

An engine is a powerful machine that needs three essential things to work: fuel, air, and a spark. The fuel, often petrol or diesel, provides the energy, while the air provides the oxygen necessary to burn the fuel efficiently. The spark, created by a spark plug, ignites the fuel and air mixture, causing a small explosion that makes the engine’s parts move. If any one of these three elements is missing – fuel, air, or spark – the lawn mower won’t start and run. These three components are equally necessary to start the engine and keep it running.

An engine is a carefully orchestrated machine, where all the parts must work together seamlessly for it to function properly. Clogs and blockages in the finely tuned moving parts can prevent the engine from working, just like a small pebble can jam a complex clock’s gears. The other parts of an engine have important roles too. Some create high voltage needed to make the spark needed to ignite the fuel, while others filter the air and fuel to ensure a smooth and efficient burn. There are also safety components that protect the user from potential harm. All these parts must be set correctly and work together harmoniously to keep the engine running and the user safe. Regular maintenance of your lawn mower will ensure your lawn mower starts properly every time. This guide will cover 99% of the problems you might encounter when starting your lawn mower. If it still doesn’t work, maybe you should consider a new model – here you’ll find the top 5 petrol lawn mowers?

Operator Presence Control (OPC) also known as “Dead man’s switch” or “Dead man’s handle”

The Operator Presence Control (OPC), also known as “Dead man’s switch”, “Dead man’s handle” or “engine flywheel brake”, is a safety feature found on many lawnmowers. Its purpose is to ensure the lawn mower’s engine and cutting blades stop running if the operator releases their grip on the handle. This safety mechanism helps prevent accidents and injuries, especially when the operator loses control of the mower or needs to stop the machine quickly. To troubleshoot the OPC, first, make sure you have moved it to and are holding it in the “run” position. Next, check for any visible damage or wear on the switch or handle. Ensure the cable connecting the switch to the engine is properly attached and not broken. The OPC is a crucial safety component that ensures the safe operation of a lawn mower, protecting both the user and those around them, and it should not be bypassed.

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Fuel is a critical component of a petrol lawnmower’s operation, and several issues can arise if it is not managed correctly. One common problem is that fuel may not reach the engine due to a clogged air/fuel filter or a malfunctioning carburettor. To solve this, tap on the carburettor to let the fuel flow through to the engine and check for clogged filters.

If the fuel filter or carburettor becomes clogged, it may prevent fuel from reaching the engine. In this case, the old fuel from the float bowl should be drained, and the carburettor should be thoroughly cleaned. If these steps do not work, the carburettor may need replacing.

Sometimes, the fuel cap can also cause problems. Without a vent, a partial vacuum forms in the fuel tank that eventually stops the flow of fuel. If the mower sputters and dies after a few passes, it could be due to the fuel cap. You should remove the gas cap to break the vacuum and then reattach it. If the mower does not start or cuts off again after a few minutes, a new gas cap may be necessary.

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You should always make sure you purchase the correct fuel for your lawn mower.

Old or stale fuel

One of the most common reasons why petrol lawnmowers won’t start initially is due to old or stale fuel. Petrol is an organic hydrocarbon and like all organic substances, it breaks down naturally over time. Gasoline has an ideal shelf life of about 30 days due to the ethanol it contains. If left inside the lawnmower for longer than this period, it can cause corrosion inside the machine and even clog the carburettor. Most people forget this and assume all is well when they see leftover fuel in the petrol tank. This can lead to unnecessary checks and changes.

To avoid problems with stale fuel, remember to replace the petrol inside the lawnmower every 30 days or so. You can also use a fuel stabilizer to keep petrol fresh for up to 3 years. However, fuel stabilizers cannot revive stale fuel. If the fuel in your mower is more than 10 to 12 weeks old, drain it and replace it with new, fresh fuel. Do not refill it with fuel from a jerry can because it is probably as old as the fuel in the mower itself. Instead, replace the whole lot with new fuel from the pump and only buy fuel you will use within a few weeks of purchase.

Check the Air Filter

A common issue that can prevent a petrol lawnmower from starting is a dirty or blocked air filter. The air filter guards the carburettor and engine against debris such as grass clippings and dirt. Over time, these particles can clog the filter and prevent the engine from starting.

To check the air filter, open the filter cover and inspect the sponge or paper filter for blockages. If the filter is dirty or torn, it must be cleaned or replaced. Depending on the type of filter, it may be sufficient to tap it regularly and apply some air filter oil.

Cleaning the filter involves washing foam filters in hot water and detergent to loosen grime, allowing it to dry completely, and wiping fresh motor oil over the filter before replacing it in its housing. On the other hand, paper filters can only be replaced.

A clean air filter is essential for the smooth operation of the lawnmower. Without it, the carburettor may be starved of oxygen, causing poor starting, poor fuel economy, and potential engine damage. To keep your mower in good condition, replacing paper filters or cleaning or replacing foam filters after every 25 hours of engine use is recommended.

If your air filter is dirty, cleaning or replacing it can be a straightforward solution. In addition to grass clippings and dirt, some air filters can get clogged with debris, such as leaves. Regular air filter inspection and cleaning can help prevent these blockages and keep your lawnmower running smoothly.

Blade Issues

Blade issues can cause a lawnmower to fail to start. If the blades are jammed or obstructed, the lawnmower won’t gain enough momentum to start. It’s important to check for any blockages around the blades.

Grass clippings can clog the mower deck, particularly when mowing a wet lawn, preventing the blade from turning. If the starter rope seems stuck or is difficult to pull, it’s likely due to a clogged deck. It’s recommended to turn the mower safely off and tip it over onto its side to examine the underbelly for large clumps of cut grass that can be removed using a trowel.

When inspecting the cutting blade, remember to turn the mower over correctly and according to the manual. You should always remove the spark plug cap before working on or near the cutting blade to avoid unexpected starts. Winter grass is tough and can quickly blunt a blade, so it’s essential to keep the cutting blade sharp. A blunt blade will give a poor cut, labour the engine causing engine wear, and increase fuel consumption. Cutting blades spin at high speeds and always need to be balanced. Debris can damage the cutting blade, causing engine strain and leading to costly repairs.

Mower cutting blades can be sharpened and balanced, and owners can refer to the owner’s manual for details or call their local dealer or mower service centre for assistance.

Choke / Flooded engine

The choke is a feature on some lawn mowers designed to assist with starting the engine, especially when it’s cold. To use the choke, pull it out before starting the engine and then push it back in once the engine is running smoothly. Be cautious not to leave the choke on for too long, as this could cause the engine to flood. However, many newer lawn mower models have replaced the choke with a primer. To use a primer, press it a couple of times before starting a cold engine. Be careful not to press it too many times, as overdoing it can also lead to a flooded engine. If you encounter issues starting your lawn mower, ensure the choke or primer is functioning properly and not causing any flooding.

If you suspect that your engine is flooded, don’t worry – there are steps you can take to resolve the issue. A flooded engine occurs when there is too much fuel and not enough air in the combustion chamber, making it difficult for the engine to start. To deal with a flooded engine, first, turn off the ignition and wait for a few minutes to allow the excess fuel to evaporate. Then, open the throttle – if your lawn mower has one – or hold down the primer button to allow more air into the engine. With the throttle open or primer held down, try starting the engine again without engaging the choke. This process should help clear the excess fuel and allow the engine to start. If the engine still does not start after several attempts, consult your lawn mower’s user manual or contact a professional technician for further assistance.


A clogged carburettor is one of the most common issues that can prevent a lawnmower from starting. This can happen when fuel is left in the mower for an extended period, causing some of the ingredients to evaporate and leaving behind a sticky substance that clogs the carburettor. If this is the case, try cleaning the carburettor with a carburettor cleaner. If that doesn’t work, it may be necessary to replace the entire carburettor.

A dirty carburettor can also cause a lawnmower to start and then die or not start at all. The carburettor mixes fuel with air to create the right fuel/air mixture for combustion. If the carburettor is dirty, it won’t be able to draw air into the engine, causing the mower to malfunction. A dirty air filter is often the culprit, as leftover petrol can condense and solidify in the filter, preventing it from pulling in the air. It’s also possible that the carburettor isn’t attached properly and is leaking air after it draws it in.

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If you haven’t cleaned the carburettor recently, it’s worth checking again to see if it needs cleaning. Many models have a primer, a manually operated fuel pump near the carburettor that can fill it with fresh fuel in a few pump strokes. This can be especially useful if the mower has been run empty or unused for an extended period. Be sure to check the primer’s functionality with a few pump strokes before attempting to start the mower.


Damaged or loose cables can lead to various problems, such as difficulty starting the engine or loss of power. To check the electrical cables, begin by turning off the mower and disconnecting the spark plug to ensure safety. Examine the cables for any signs of wear, fraying, or damage, paying close attention to the connections at the battery, solenoid, and starter motor. Make sure the connections are clean, tight, and free of corrosion. If you notice any damaged cables, replace them promptly to avoid further complications.

Check the Spark Plug

Experiencing difficulty starting your petrol lawnmower might indicate a problem with the spark plug, which is responsible for igniting the fuel in the engine. Over time, spark plugs can become dirty, corroded, or disconnected. To inspect the spark plug, first, remove the lead and then carefully unscrew the plug using a spark plug spanner/socket. Examine the end of the plug for any signs of wetness from petrol, which could point to a carburettor blockage. Check the fuel line by removing and blowing through it to ensure it’s clear. If the plug is dry and the fuel line is clear, the issue is likely with the carburettor, which should be cleaned by a professional if you’re inexperienced in handling it.

If the spark plug appears wet or has visible corrosion, burns, or sludge, it’s best to replace it rather than clean it. For cleaning, use a grease-cleaning solution or solvent and gently sand the contacts. Make sure the gap is set correctly, as specified in the user manual. Always have a spare spark plug handy in case of a sudden malfunction.

When inspecting the spark plug, pay attention to the electrode and insulator for any buildup. If present, spray brake cleaner on the plug, let it soak for a few minutes and then wipe it clean. Reinstall the spark plug by hand before using a socket wrench to tighten it. If the problem persists, consider replacing the spark plug.

The spark plug’s condition can also be assessed by unscrewing it from the motor and visually inspecting it. If the electrodes have a metallic or fawn colour without soot, the spark plug can typically be used for another season. Slight discolourations can be removed with a wire brush. However, if the spark plug is black or oily, there may be a defect in the system that needs urgent repair. When purchasing a new spark plug, make sure the type designation is correct, which can be found on the ceramic body. Check the manual to make sure the new spark plug is compatible.

Check the oil

Regularly checking the oil levels in your lawn mower is important to prevent serious damage to the engine. Most lawnmowers have a dipstick to check the oil. Locate the dipstick, remove it, and wipe it off with a clean cloth. Reinsert the dipstick into the engine and remove it again to get an accurate reading for the oil level. Top off the oil if necessary, and ensure you use the recommended oil for your lawn mower. Regularly checking your lawn mower’s oil levels can help increase its longevity, reduce the chance of engine failure, and keep your lawn mower running smoothly.

The correct oil type can be found in the owner’s manual. Using the wrong oil can reduce efficiency and risk permanent damage.

Depending on the age of the engine oil, it may be time for an oil change. For commercial 4-stroke lawn mowers with normal use, it is recommended to change the oil once a year, ideally in the spring. An oil change should occur every 25 operating hours for petrol mowers with heavy use. The first oil change should occur after 5 to 6 hours of operation for newly run-in lawn mowers. These short change intervals compared to a car are because lawn mower petrol engines usually do not have an oil filter, making the oil dirtier more quickly.

Remember that the oil level should be checked not just at the start of the season but at regular intervals to ensure the longevity of the mower’s engine.


If your lawn mower features an electric start, it relies on a battery to provide the power needed for the engine to start. A charged battery is essential for the smooth operation of your mower. A flat battery could be the culprit if you’re experiencing difficulties starting your lawn mower.

To troubleshoot a flat battery, follow these steps:

Check the battery connections: Make sure the connections between the battery and the mower are clean and secure. Corrosion or loose connections can impede the flow of electricity, preventing the mower from starting.

Test the battery voltage: Using a multimeter, measure the voltage of the battery. A fully charged battery should read around 12.6 volts or higher. If the voltage is significantly lower, the battery may be flat or faulty.

Charge the battery: If the voltage reading is low, connect the battery to a compatible charger and allow it to charge for the recommended amount of time. Consult your lawn mower’s user manual for specific charging instructions.

Test the battery again: After charging the battery, measure the voltage once more using the multimeter. If the voltage remains low despite charging, the battery may be damaged or have reached the end of its lifespan, and a replacement may be necessary.

Check the charging system: If the battery continually loses charge or becomes flat, there could be an issue with the lawn mower’s charging system. In this case, consult your user manual or contact a professional technician for assistance.

Starter Solenoid

The solenoid is an essential component in a lawn mower’s electrical system, responsible for transferring electrical current from the battery to the starter motor when you turn the ignition key. Essentially, it acts as a switch, enabling the engine to start when needed. To troubleshoot a solenoid on a lawn mower, begin by ensuring the battery is charged and properly connected. If the engine still fails to start, locate the solenoid (often found near the battery or starter motor) and check its connections for any signs of corrosion, wear, or damage. Clean and tighten the connections as necessary. If the issue persists, use a multimeter to test the solenoid’s functionality by measuring the voltage at the input and output terminals while turning the ignition key. If the voltage reading does not change when the key is turned, the solenoid may be faulty and need replacement.


The information in this article should cover 99% of the issues stopping your lawn mower from starting. With the help of this article, you will be able to diagnose and repair any lawn mower that won’t start. You’ll learn how to check for spark plugs, fuel lines, air filters, fuel tanks and other possible causes of a lawn mower not starting. Also included are tips on when to replace parts or when it’s time to call in a professional. We hope this article helps you get your lawn mower running like new again!

Please read through each of the troubleshooting steps and be sure to follow all safety precautions before starting any repairs.

What to do If My Lawn Mower Won’t Start

After being in storage for the winter months, your lawn mower might not want to start at the first turn of the key. This is common, so don’t get too concerned right away. Continue reading to see what to do if your lawn mower isn’t starting for you.

Do you need lawn mower service right now? Get in touch with the team at Koenig Equipment to get the support you need and schedule an appointment with us today!

What’s the starting procedure for my lawn tractor?

The standard starting procedure for lawn tractors is rather simple and the same across most lawn mowers.

  • Put the choke lever in the full choke position.
  • Turn the key to crank the engine for about five seconds.
  • If your engine hasn’t started from the above steps, let the engine rest for about 10 seconds and then crank the engine for another five seconds. If the engine sounds like it is about to start, you can crank it slightly for more than five seconds.

In addition to the above steps, if you have a riding lawn tractor, there is a seat sensor included for safety. If you are not sitting in the seat, the sensor will know, and the mower will not start. For push mowers, there is a safety handle.

Is the problem with the battery or with the starter?

If you are going through the proper starting procedure with your lawn tractor and it is not starting, it is time to check the battery and the starter. The best place to start with is the battery. Without enough electricity, an engine starter problem can’t be diagnosed. Check to ensure that all the connections are properly hooked up to the battery. If the lawn tractor still won’t start, you can try jump-starting it. Jump-starting your lawn tractor will rule out a weak battery. You can also utilize a voltmeter to test your battery health and strength.

After confirming your battery is not the problem, you can look towards the starter. An easy sign to see if the starter is your problem is if it makes a clicking sound when you are trying to start the lawn tractor by turning the key. If this is the case, we may recommend replacing the starter, but it will take a service appointment to correctly diagnose the issue.

Is there a difference between starting in cold weather and warm weather?

The starting procedure discussed above is the same for starting a lawn tractor in either cold or warm weather. If you are using your lawn tractor for tasks during cold winter months, make sure you are using the proper oil for the temperature. Some oils aren’t made for lower temperatures and can become thicker in the winter months, causing your equipment to not start properly. Your local technician or parts specialist can help you choose the right oil for winter weather.

Is it common to have starting problems after storage?

Starting problems with your lawn tractor can be rather common after storage. Before you put your equipment away for winter storage, be sure you are winterizing your lawn tractor properly to help reduce any starting problems in the spring. Ensuring you winterize your lawn tractor before storage will make it much easier to start up when you bring it out again.

Where can I find lawn tractor service near me?

When it comes time to mow again, you want your lawn tractor to work properly and start easily for the upcoming season. If you get your lawn tractor out and have issues starting it, even after following the standard starting procedure and checking the battery and spark plugs, the certified team at Koenig Equipment is here to help.

With the certified service department at each Koenig Equipment location, you can rest assured knowing they will solve any issues that may arise with your lawn tractor.

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