Lawn mower fault finding. Electric Lawn Mower Not Starting? It’s One Of 12 Issues

Electric Lawn Mower Not Starting? It’s One Of 12 Issues

Well, wouldn’t you know it? You’ve got the time finally to attack the lawn you’ve been meaning to get to and what happens? Nothing.

Not because of anything you’ve done. No, you’ve planned to get this done.

Yet, regardless of all your planning, your trusty electric mower just won’t start.

Okay, maybe that’s all a bit dramatic. Perhaps you just figured it was as good a time as any to hit the lawn with a well-deserved trim. Or maybe there’s a storm coming through and you wanted to get the mowing done before the grass became saturated for a few days.

Regardless of the circumstances, the main thing is your mower isn’t cooperating, so there’s not going to be any mowing until you figure out what the issue is. That’s the dramatic part.

Just remember, when it comes to an electric mower not starting, whether it’s a corded or battery-powered mower, it will probably be an issue with the power supply (outlet/breaker or battery charger), power transmission (cord or battery), or the mower itself (breakers, connections, motor control switches, etc).

Before you start tearing anything apart in a desperate attempt to get your mower, well, mowing, below are some things to troubleshoot and things to consider that might fix the problem before you have to get a technician or service center involved.

Safety First

First, let’s go ahead and get this out of the way. Always remember safety first when it comes to troubleshooting any kind of equipment that can either cut off fingers or electrocute you or both. That’s a bad day that should be avoided at all costs.

Second, have your manufacturer’s manual (or owner’s manual, whichever you prefer) available. If you don’t have a hard copy, you can probably find it online by doing a Google search that looks like, “[Your Brand] [Model Number] Manual PDF.”

Once you have that ready, you’re ready to start troubleshooting.

Troubleshooting Processfor a Corded or Battery-Powered Mower

Before we get to the specific electric mower you have, the troubleshooting process will follow essentially the same path in this general order:

• Inspect the power transmitter (the cord for a corded mower and the battery for the battery mower).
• Insect the power supply (the outlet and circuit breaker for a corded mower and the battery charger for the battery mower).
• Inspect the power receiving end on the mower.
• Consult your warranty information and contact service center if necessary.

A Corded Electric Mower

Before we determine what the power issue with your electric mower may be, first it helps to know the type of electric mower you have. In this case, let’s assume you have a corded mower.

Let’s also assume that, until this moment, you’ve had zero issues with the mower when it comes to starting and stopping it or anything related to sources of power.

Now, let’s troubleshoot.

Inspect the Cord

If it is a corded electric mower then the first thing you’re going to want to do is to inspect your cord. As most corded mowers do not come with a manufacturer’s provided cord, you have to provide your own extension cord. It should be a standard 16-gauge grounded cord and free of any cuts or other visible damage. Also, check the prongs on the male end and the female end for damage. Lastly, check the male end on the mower itself.

Inspect the Outlet and Breaker

If you’re satisfied the cord is good, try plugging it into another item from the same wall outlet. If there’s no power at the outlet, then you’ve probably identified the issue. It could be a loose wire, a bad outlet, or a tripped breaker. Check one after another until you find the problem.

Check the Breaker and Motor Control Switch

If there isn’t a problem at the outlet or breaker and the cord successfully powers something other than the mower, then the issue is probably at the mower itself.

At this point, check the connection at the mower again to make sure it’s tight and holding firm.

From here, go to the breaker on the mower itself. Push RESET and see if the mower has power now. If it does, there was your problem. If it doesn’t then you may have a bad motor control switch. At this point, unless you know how to repair or replace such a switch, you’ll probably need to consult a service center or repair technician.

Warranty and Corded MowerTroubleshooting Review

One thing to check that’s not on the mower but applies to it is how old it is and if you still have a warranty on it, whether it’s a manufacturer’s or from the store it was purchased at. If you still have a warranty, don’t do any more work on the mower and place that warranty-issue call to get it fixed.

That pretty much sums it up for a corded electric motor. If it isn’t starting, check the power supply at the plug and main breaker, the power transmission at the cord, and final the power receiving at the mower itself. Do that in that order. From there, if you can’t identify the problem, time to call for help.

A Battery-Powered Electric Mower

Okay, now if you don’t have a corded electric mower but a battery-operated model, then this section is for you. However, you should still read through the corded mower section because you might pick up on something there that might help someone you know down the road.

Like the corded mower, let’s assume your mower has functioned normally until this moment and, unexpectedly, it’s just not starting.

Well, clearly there’s a power issue of some sort. So, let’s get to troubleshooting.

Inspect the Battery

With inspecting the battery, you should be looking for any kind of visual damages or leaks. Also, check the battery light to ensure it does indicate a charge. It might not be true but check all the same.

While inspecting, also make sure the battery is dry. A damp or wet battery can cause a short, lead to overheating, and cause a breakdown. If you believe this happened, you shouldn’t have a solid charge on the battery at all.

Speaking of charges, if everything looks good, and you have a battery tester, this would be an ideal time to test it. That way, if it’s not showing a charge even though the indicator lights up green, then you know the battery is probably bad and needs replacement.

Inspect the Battery Charger

If your battery is charged and you’ve tested it and you’re confident it is, then your battery charger should be operating properly. However, if you’ve got no charge on the battery after testing it, check the charger to see if there’s an issue there.

One way to test the charger is, of course, to put another battery on it and see if it charges. However, not everyone has extra lawn mower batteries. Really, the only thing you can do here is to inspect the charger for damage, check the outlet, and inspect the breaker as you would do with a corded mower.

Another thing you can do is use a volt meter. A positive result would indicate that a charger is at least supplying energy but the battery probably can’t hold a charge for long. A negative result would indicate that the charger itself is bad.

Store Your Mower in a Dry Place

Another tip that sounds obvious but one that’s very important when it comes to electric mowers. Remember, water can seriously damage an electric mower, especially a battery-operated one.

Store Your Cord and Battery After Use

Don’t leave the cord with the mower where it can get damaged. Store it somewhere it is easy to get to but won’t be affected by things like sharp blades or wheels. You get it.

For batteries, remove them after use and charge them but don’t leave them on the charger all the time. Also, don’t run the battery completely dead all the time. Running a battery to both extremes can diminish its service life quicker than normal.

Visually Inspect the Mower Before Use

Again, it sounds obvious but it’s good advice, especially if you haven’t taken a look at the blades in a while.

Conclusion

When you use equipment that runs on electricity or gas, eventually you’ll have an issue that needs some special troubleshooting attention. The good news is, with electric mowers, it doesn’t take much time to figure out what the issue might be and when you’ll need to call for assistance.

Just remember to always be safe, walk through the steps, and be patient. Electricity is a wonderful thing but it isn’t magic. Be safe and remember to call for help if you need it.

I’ve been helping homeowners with appliance repair since 2016. Starting out as an enthusiastic amateur, I’ve since worked with many Appliance, HVAC, and DIY experts over the last 7 years. My mission is to help your fix your appliances and systems. saving you money and lowering your energy bills. Visit my author page to learn more! Read more

Hi there! My name’s Craig, and I started Appliance Analysts back in 2017.

My mission is to help our readers solve appliance-related issues without paying through the nose for contractors or a whole new model. I’m joining up with experts from across the HVAC, Appliance Repair, DIY industries to share free expert advice that will save you time, stress, and money.

Lawn mower won’t start troubleshooting video: fuel, ignition and compression problems video

A clogged air filter, bad spark plug or contaminated gas can prevent your walk-behind lawn mower from starting. Troubleshoot the problem with this Sears PartsDirect video, which shows how to check engine compression, clean the fuel line and look at the choke linkage, return spring and carburetor.

Check out our DIY Walk Behind Mower Repair page for more troubleshooting videos, repair guides and answers to commonly asked questions.

Today we’re talking about some troubleshooting steps to figure out why your lawn mower won’t start. Although your mower might look different from this Craftsman 21-inch mower, they all work pretty much the same.

These are the tools and supplies you might need, depending on the problem.

Tools and equipment needed

• Starting fluid
• Fresh gasoline
• Ratchet and deep socket
• Spark plug tester
• Compression gauge
• Shop rag
• Fuel-safe container
• Pipe cleaner
• Carburetor or carburetor rebuild kit

Fuel, spark and compression

Since we’ll be working around gasoline, choose a well-ventilated area free of open flame or sparks.

For an engine to start and run when you pull the recoil starter rope, it needs 3 things. The first is fuel, which is a combination of gasoline and air that mixes in the carburetor. Then it needs a spark from the spark plug to ignite that fuel in the cylinder. Finally, it needs the right amount of compression in the cylinder to drive the piston. To fix your problem, we’ll have to figure out which of these three is missing.

We’re going to start by checking a few easy things.

Check the air filter

A clogged air filter can keep air from getting to the carburetor and mixing with the gas.

Remove the air filter cover and pull out the air filter. This mower has a pleated paper filter, but yours might be a different type of paper filter, or it might be foam. If you have a paper filter that’s just a little dirty, you can tap the filter on a hard surface to clean it. If it’s completely clogged, then you need to replace it. If your mower has a foam air filter, you can find cleaning instructions in your owner’s manual.

Check for a fuel problem

While the air filter is removed, let’s do a quick test to see if the engine has a fuel problem. Spray starting fluid through the air filter opening to the carburetor and then try to start the engine.

If it doesn’t start, that eliminates a fuel problem, leaving spark and compression on our list of suspects. If the engine starts and runs briefly, click here to skip to the section about diagnosing fuel problems.

Spark plug and compression

Check the spark plug first. Pull off the spark plug wire and remove the spark plug, using a ratchet fitted with a deep socket. Look for carbon or oil buildup on the spark plug electrode that could prevent sparking. Also, look for a crack in the ceramic insulator. If you see excessive buildup or a crack, replace the spark plug.

If the spark plug looks good, reinstall it and then connect a spark plug tester to check the ignition system. Release the rope from the mower handle so it’s in reach when testing the spark plug. Connect the tester boot to the spark plug and connect the spark plug wire to the other end of the tester. Clamp the bail control bar down to release the blade brake. Pull the starter rope and see if the tester sparks. If the tester shows that there’s no spark, follow the steps in our video about troubleshooting the ignition system.

If the spark plug is good and the ignition system works, check the cylinder compression. You need a compression gauge for this test.

First, remove the spark plug from the cylinder and pull the starter rope several times to purge fuel or oil from the cylinder. Insert a compression gauge in the spark plug hole and push the button to zero-out the gauge. Pull the starter rope repeatedly, until the needle on the gauge stops rising. The gauge should measure between 40 and 60 psi of compression. If it’s lower than 40 psi, have a service technician examine the engine and fix the compression problem. The technician has the right tools and the expertise to diagnose low compression.

Testing the gas, tank

Now, if the engine started and ran briefly when you did the starting fluid test, you know the spark and compression are okay and the problem is in the fuel system. For these tests, be sure you’re in a well-ventilated area where gas fumes can’t build up.

First, let’s look at the condition of the gas. Old gas that has absorbed water or gas that has dirt in it can keep a mower from starting. If your gas has been sitting around a while—either in the tank or in the can—drain the tank and fill it with fresh, clean gas from a clean gas can.

In the future, if you’re going to leave gas in the tank for a while, add fuel stabilizer.

To drain the tank, lay a shop rag on the mower deck below the tank to catch spills. Place a clean, durable container under the fuel line connection on the bottom of the tank. Release the fuel line clamp and pull the fuel line off to drain the gas into the container. For information on disposing the gas safely and legally, check with your local fire department or hazardous waste recycling center.

If you find debris in the drained gas, check for a contaminated fuel tank. Use a flashlight to look inside the tank for grass or debris. If you see debris, release the rope from the mower handle and then remove the three screws from the lower housing. Remove the blower housing and pull the tank off the engine. Rinse out the tank with water and let the tank dry completely before reassembling the mower. Don’t pour that water down a drain. Dispose of it correctly along with the old gas.

Checking the filter screen, fuel Line

After rinsing out the fuel tank, check the filter screen at the bottom of the gas tank for damage. On this style of engine, the screen isn’t available as a separate part, so if the screen is damaged, you have to replace the tank. Some tanks have a removable fuel filter that you can clean or replace. Check your owner’s manual for more information.

You should also check the fuel line for a crack or clog. Disconnect the other end of the fuel line from the carburetor. Examine it for cracks or cuts and replace it if it’s damaged. If you don’t see any damage, look through the fuel line and clear any clogs with a pipe cleaner.

Determining carburetor issues

If you’ve ruled out the quality of the gas and the fuel line, it’s time to turn to the carburetor, which mixes gas and air that is drawn into the cylinder.

Let’s start with the carburetor choke plate. The choke plate controls the ratio of gas and air sent to the carburetor depending on engine temperature. The engine on a lawn mower that’s been idle for more than an hour is cold and needs less air to start. In this case, the choke plate should close to temporarily restrict airflow through the carburetor so more fuel can enter the cylinder.

A choke plate that’s stuck open could prevent the cold engine from starting. Check the choke plate by looking through the carburetor air inlet on the air filter base. The choke plate should be fully closed. If the choke plate is open, check the choke thermostat and linkage. First, remove the air filter base to access the choke linkage and choke thermostat. Remove the blower housing if you didn’t already remove it to rinse out the fuel tank.

Examine the choke linkage and return spring to see if they’re connected properly and moving freely. Reconnect the choke linkage and return spring and replace any broken parts. If the choke linkage and return spring looked good, then your choke thermostat is likely stuck. Replace the choke thermostat if it’s stuck in the open position.

Instead of a choke plate, some engines have a primer bulb that you press to force more fuel into the cylinder when starting a cold engine. Replace the primer bulb if it’s damaged.

Replace or rebuild carburetor

If the choke plate or primer bulb work, it’s likely you need to replace or rebuild the carburetor. Here’s a video that shows you how to replace the carburetor.

Or, you could rebuild the carburetor, which takes more effort but costs less. Order the carburetor rebuild kit and then clean and rebuild the carburetor if you want to save money on parts. Here’s a video that shows how to rebuild the carburetor.

Once you restore the fuel flow to the engine cylinder by replacing or rebuilding the carburetor, the engine should start.

I hope that this video helps you out today. Be sure to check out our other videos, here on the Sears PartsDirect YouTube Channel, and subscribe if you like them.

Lawnmower Won’t Start? Do this.

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

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

How to Fix a Lawnmower That Won’t Start

Replace the Bad Gas

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

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

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

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

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

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

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

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

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

Clean the Carburetor

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

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

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

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

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

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

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

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

Clean/Replace the Air Filter

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

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

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

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

Check the Spark Plug

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

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

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

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

Did You Hit a Rock or Other Obstacle?

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

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

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

My Lawnmower Starts But Runs Poorly

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

Add Gasoline Stabilizer to Avoid Most of These Problems

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

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

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

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

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

Use a Good Motor Oil for Your Lawnmower

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

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

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

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

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

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

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

My 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.

Fuel

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.

Ignition

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.

Precautions

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.