There are a number of reasons, mechanical and otherwise, why a mower won’t run. The good news is that fixing most all of the issues is easy enough for a DIYer to handle.
By Tony Carrick and Manasa Reddigari | Updated Aug 8, 2022 4:03 PM
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Lawn care can be tedious, but once the grass starts growing in the spring, mowing becomes a fact of life in most neighborhoods. When you finally muster the strength to tackle that first cut of the season, there are few sounds as disheartening as that of a lawn mower engine that turns over but doesn’t start.
Before you drag the mower in for repairs or invest in costly replacement parts, first make sure that a clogged air filter, soiled spark plug, damaged safety cable, clogged mowing deck, or contaminated gas isn’t to blame. Work through the following steps, and you may be able to get your puttering grass guzzler up and running again in no time.
A lawn mower repair professional can help. Get free, no-commitment repair estimates from pros near you.
Change the lawn mower carburetor filter.
Your lawn mower’s air filter guards the carburetor and engine from debris like grass clippings and dirt. When the air filter becomes clogged or too dirty, it can prevent the engine from starting. To keep this from happening, replace paper filters—or clean or replace foam filters—after every 25 hours of engine use.
The process for removing the filter depends on whether you are operating a riding or walk-behind lawn mower. For a riding mower, turn off the engine and engage the parking brake; for a walk-behind mower, pull the spark plug wire from the plug. Then, lift the filter from its housing.
The only choice for paper filters is replacement. If you’re cleaning a foam filter, wash it in a solution of hot water and detergent to loosen grime. Allow it to dry completely, and then wipe fresh motor oil over the filter, replace it in its housing, and power up the mower—this time to the pleasant whirring of an engine in tip-top condition.
Check the spark plug.
Is your lawn mower still being stubborn? The culprit may be the spark plug, which is responsible for creating the spark that ignites the fuel in the engine. If it’s loosened, disconnected, or coated in water or carbon residue, the spark plug may be the cause of your machine’s malfunction.
Locate the spark plug, often found on the front of the mower, and disconnect the spark plug wire, revealing the plug beneath. Use a socket wrench to unscrew the spark plug and remove it.
Check the electrode and insulator. If you see buildup, spray brake cleaner onto the plug, and let it soak for several minutes before wiping it with a clean cloth. Reinstall the spark plug, first by hand, and then with a socket wrench for a final tightening. If the problem persists, consider changing the spark plug.
Clear the mower deck of debris.
The mower’s deck prevents grass clippings from showering into the air like confetti, but it also creates a place for them to collect. Grass clippings can clog the mower deck, especially while mowing a wet lawn, preventing the blade from turning.
If the starter rope seems stuck or is difficult to pull, then it’s probably due to a clogged deck. With the mower safely turned off, tip it over onto its side and examine the underbelly. If there are large clumps of cut grass caught between the blade and deck, use a trowel to scrape these clippings free. When the deck is clean again, set the mower back on its feet and start it up.
Clear the vent in the lawn mower fuel cap.
The mower started just fine, you’ve made the first few passes, then all of a sudden the mower quits. You pull the cord a few times, but the engine just sputters and dies. What’s happening? It could have something to do with the fuel cap. Most mowers have a vented fuel cap. This vent is intended to release pressure, allowing fuel to flow from the tank to the carburetor. Without the vent, the gas fumes inside the tank begin to build up, creating a vacuum that eventually becomes so strong that it stops the flow of fuel.
To find out if this is the problem, remove the gas cap to break the vacuum, then reattach it. The mower should start right up. But if the lawn mower won’t stay running and cuts off again after 10 minutes or so, you’ll need to get a new gas cap.
Clean and refill the lawn mower fuel tank.
An obvious—and often overlooked—reason your mower may not be starting is that the tank is empty or contains gas that is either old or contaminated with excess moisture and dirt. If your gas is more than a month old, use an oil siphon pump to drain it from the tank.
(It’s important to be careful as spilled oil can cause smoking, but there are other reasons this might happen. Read more about what to do when your lawn mower is smoking.)
Add fuel stabilizer to the tank.
Fill the tank with fresh fuel and a fuel stabilizer to extend the life of the gas and prevent future buildup. A clogged fuel filter is another possible reason for a lawn mower not to start. When the filter is clogged, the engine can’t access the gas that makes the system go. If your mower has a fuel filter (not all do), check to make sure it’s functioning properly.
First, remove the fuel line at the carburetor. Gas should flow out. If it doesn’t, confirm that the fuel shutoff valve isn’t accidentally closed. Then remove the fuel line that’s ahead of the fuel filter inlet. If gas runs out freely, there’s a problem with the fuel filter. Consult your owner’s manual for instructions on replacing the filter and reassembling the mower.
Inspect the safety release mechanism cable.
Your lawn mower’s reluctance to start may have nothing to do with the engine at all but rather with one of the mower’s safety features: the dead man’s control. This colorfully named safety bar must be held in place by the operator for the engine to start or run. When the bar is released, the engine stops. While this mechanism cuts down on the likelihood of horrific lawn mower accidents, it also can be the reason the mower won’t start.
The safety bar of a dead man’s control is attached to a metal cable that connects to the engine’s ignition coil, which is responsible for sending current to the spark plug. If your lawn mower’s engine won’t start, check to see if that cable is damaged or broken. If it is, you’ll need to replace it before the mower will start.
Fortunately, replacing a broken control cable is an easy job. You may, however, have to wait a few days to get the part. Jot down the serial number of your lawn mower, then head to the manufacturer’s website to order a new cable.
Check to see if the flywheel brake is fully engaged.
The flywheel helps to make the engine work smoothly through inertia. When it isn’t working properly, it will prevent the mower’s engine from working.
How to Fix a Riding Lawn Mower Doesn’t Crank or Click
If it is fully engaged, it can make a mower’s pull cord hard to pull. Check the brake pad to see if it makes full contact with the flywheel and that there isn’t anything jamming the blade so the control lever can move freely.
If the flywheel brake’s key sheared, the mower may have run over something that got tangled in the blade. It is possible to replace a flywheel key, but it does require taking apart the mower.
Look out for signs that the mower needs professional repairs.
While repairing lawn mowers can be a DIY job, there are times when it can be best to ask a professional to help repair a lawn mower. If you’ve done all of the proper mower maintenance that is recommended by the manufacturer, and gone through all of the possible ways to fix the mower from the steps above, then it may be best to call a pro. Here are a few signs that indicate when a pro’s help is a good idea.
- You see black smoke. The engine will benefit from a technician’s evaluation, as it could be cracked or something else might be worn out.
- Excessive oil or gas usage. If you’ve changed the spark plugs, and done all of the other maintenance tasks, and the mower is consuming more than its usual amount of oil or gas, consult a professional for an evaluation.
- The lawn mower is making a knocking sound. When a lawn mower starts making a knocking sound, something could be bent or out of alignment. It may be tough to figure this out on your own, so a pro could help.
- A vibrating or shaking lawn mower can be a sign of a problem beyond a DIY fix. Usually something is loose or not aligning properly.
Learn the reasons why a lawn mower won’t start after winter or during peak season, and how to fix those problems.
Family Handyman
Introduction
Most of the time when a lawn mower won’t start the cause is a problem with the gas or the lawn mower carburetor.
What to Do if Your Lawn Mower Won’t Start
Whatever kind of lawn mower you’ve got, the last thing you want once winter finally lifts and spring has sprung is a lawn mower that won’t start.
If you’ve taken the proper steps to winterize your lawn mower, you’re far less likely to be dealing with such issues. It’s also why you should tune up your lawn mower at the start of every season. However, it’s not out of the ordinary to find your gas-powered lawn mower not starting from time to time, so it’s important to know why your lawn mower isn’t starting and how to fix it.
Project step-by-step (6)
Check the Gas Tank
Let’s start with the obvious. Before you have a heart attack pulling on the rip cord, you’ll want to check the fuel. Like any gasoline-powered engine, lawn mowers run out from time to time. Maybe you forgot it was running on fumes when you finished mowing last time. It sounds simple, but we’ve all overlooked the gas tank from time to time.
Even if there is gas in the mower, if the fuel’s been in there more than a month, that could be the problem. Gas sitting around too long in the tank can get contaminated with dirt and extra moisture.
So if your gasoline has been in the mower for more than month, drain the gas properly, dispose of it correctly, and fill up the mower with new gas. It may take quite a few pulls to suck the new gas into the lawn mower carburetor, so be prepared to clean and dry the plug a few more times.
Add fuel stabilizer when you fill up the tank to help protect the gasoline in there from dirt and moisture.
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Check the Spark Plug
Start by making sure the lawn mower spark plug cable is connected to the plug itself. It’s quite possible that it got pulled off there over the winter while the mower was being stored in the garage.
If that’s not the issue, the next step is to remove the spark plug to see if it’s wet. There’s no way the engine will start if it is. So clean the plug with carburetor cleaner and let it dry. Cleaning it with compressed air isn’t enough; you need a solvent to remove oil residue. If it’s really grimy and dirty, it might be best to change the spark plug.
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Check for Debris in the Mower Deck
Grass clippings can get clogged in the mower deck, which can prevent the blade from turning. This is a common problem if you’ve cut wet grass or let the lawn get especially long and bushy between cuttings. If the cord is hard to pull, that’s a good sign that there’s debris clogging up your mower’s deck.
This is a pretty easy problem to solve. With the mower off, flip it on its side or upside down and scrape out the gummed up grass clippings. Once that’s done, you can flip it back over and start it up again.
JJ Gouin/Getty Images
Check the Air Filter
The lawn mower’s carburetor regulates the mix of gasoline and air going into the engine where it’s burned to create power. Before air goes into the carburetor it passes through the air filter which prevents dirt and debris from getting into it.
If the air filer is clogged or dirty, it throws the ratio out of whack. Sometimes that results in your lawn mower smoking, and sometimes it prevents it from starting entirely. So take a look at the air filter to see if it’s dirty. If so, you can clean it or just change it outright.
Robert Maxwell for Family Handyman
Check the Carburetor
Another common reason for a lawn mower that won’t start is a clogged or dirty carburetor. It can also cause your mower to run rough or spew black smoke when you’re trying to cut the grass. If that’s the case, you may need to clean the carburetor.
To get to the carburetor, you’ll have to remove the air filter. Once that’s out of the way, you can remove the carburetor in order to clean it.
Once it’s out, check for corrosion. If you see chalky/powdery white corrosion like this, it’s probably better just to replace it. To clean it, take it apart and spray carburetor cleaner on the parts and inside the housing. After that, put the carburetor back together and reinstall it in the mower.
Check the Fuel Filter
Like the air filter, the fuel filter prevents dirt and debris from getting into the combustion chamber of your lawn mower’s engine, taking that stuff out before the gas gets mixed with air in the carburetor. Problems with the fuel filter might also result in the engine sputtering or rough idling, even before it gets to the point of preventing the mower from starting.
To start, tap the side of the carburetor to help the flow of gas. If that doesn’t work, you might have a clogged filter.
Not all lawn mowers have a fuel filter, but for the ones that do, it’s usually located in the fuel line or the fuel tank. To find out where the fuel filter is at, check your lawn mower’s owners manual, which will also tell you what type of filter it is.
If the filter is in the fuel tank, you’ll need to drain the gas from the mower into a drain pan, assuming you can’t run the engine until it’s out of gas. If the filter is in the fuel line, clamp off the fuel line before removing the filter. Once you have the filter off, you can check to see if it’s dirty and clogged by holding it up the light. If it is, install a new one. Make sure it works with this lawn mower maintenance checklist.
How To Start A Lawn Mower
There’s a first time for everything – taking your first steps, trying your first Vegemite on toast, and starting a mower. And if you’ve never used a lawn mower before, it can feel a little intimidating to get going.
No shame in Googling how to start a lawn mower – and we’re here to help!
For a gasoline mower, position the throttle lever, then hold the engine brake lever securely. Firmly grasp the starter cord and pull, then guide the rope back to the engine.
For a ride-on lawn mower, press the clutch and set the parking brake. Keep the gear and throttle lever in a neutral position. Then use the key to switch on the engine.
Need to mow your lawn? Let’s get down to the basics.
Before Starting Your Lawn Mower
Don’t yank the starting rope right away! Before starting to mow, go around your lawn and remove any yard debris, toys, rocks, and other things that could damage lawn mowers.
You may also want to assess whether to level your lawn for easier mowing.
Once your lawn is ready, double-check your lawn mower – especially if it’s after winter.
Ensure you have enough gas, and refill if necessary. Use the dipstick attached to check the oil level. (Wipe the dipstick clean afterwards!)
How to Start a Lawn Mower
Always start by positioning your lawn mower on a level surface, away from tall grass.
Once you’re sure about gas fill, oil levels, and other mechanisms, get ready to start!
How to start a push lawn mower
First, ask – do you need to prime the engine? If you haven’t used your manual lawn mower in some time (e.g. over winter), then you’ll need to prime it first.
Push the petrol button or the primer button 3–5 times so gas flows into the engine. Otherwise, you can skip this step.
Next, place the throttle (between housing and handle) into position. Pull the engine brake lever (top of the handle) towards you and hold it securely.
Grasp the pull cord and pull it firmly away from the mower. You may have to do this a few times for the fuel to properly ignite.
Do not let the pull cord snap back – that’s bad for the engine. Instead, guide it back into place without letting go of the engine brake yet. Then you’re good to go!
How to start a ride-on lawn mower
Ride-on mowers use a different start-up process. Once you’ve gotten in the seat, press the clutch down and set the parking brake. Make sure the gear shift is in neutral.
If you’re starting a cold mower (one that hasn’t been used in a while), you’ll need to pull the choke control knob to open. Otherwise, leave it in place.
Set the throttle lever to neutral (between fast and slow). Then insert the ignition key into the switch and turn to start.
If your engine doesn’t start after you’ve cranked it for 15 seconds, switch it back off and wait 10 seconds. Then turn the key again.
Let the mower warm up first before changing gears or putting attachments.
Why Won’t My Lawn Mower Start?
Maybe you’re out to do some lawn care, and you yank on the starter cord… but your mower fails to turn on. There could be several reasons why your lawn mower won’t start – here are some common ones.
If you’ve gone through all these checks and your mower still won’t start, you may want to take it to a repair shop. Or you could choose one of these recommended lawn mowers to replace it.
Fuel issues
The first thing you should check if your mower won’t start is the gas tank. Don’t blow out your shoulder by yanking at the pull cord when it turns out you just forgot to refill your fuel.
Alternatively, maybe you do have gas, but it’s a month old and therefore contaminated.
If your gas tank is empty, all you need to do is refill it.
But if you’ve got contaminated gas, you’ll need to drain the fuel and refill the tank. You can add a fuel stabiliser for more protection.
Dirty spark plug
If you do have good fuel in your tank but the engine won’t start, it might be the spark plug. Dirty, loose, or disconnected plug pins can prevent fuel ignition, which means your mower won’t turn on.
Check the spark plug for any issues. If it’s loose or disconnected, screw it back into place. On the other hand, if it’s dirty, unscrew it and clean it using a clean cloth and some rubbing alcohol.
Jammed mower deck
Grass clippings and other debris can build up in your mower deck the more you mow – especially when mowing a wet lawn. The debris jams the blades and mechanisms, which stops the mower from running.
Switch off the lawn mower before you tip it on its side (and be careful – you could spill oil, which could cause white smoke ).
Check the deck to see if there are clumps of grass and twigs underneath. Remove them with a trowel, then reset your mower. Be mindful of the blade!
Blocked fuel cap
Sometimes your mower starts, sputters, then dies and refuses to start again.
If this is the case, check your vented fuel cap or gas cap. The vent is meant to release pressure so the gas fumes don’t build up and stop the flow of your fuel. But if the cap clogs up or breaks, it’ll prevent gas flow.
Shut off your mower and let it cool, then remove the gas cap. That’ll break the internal vacuum and let the fuel flow again. If your engine still sputters after starting it up, you may need a new fuel cap.
Clogged carburettor filter
The carburettor is responsible for regulating the mixture of fuel and air for engine combustion.
It comes with an air filter that prevents debris from entering the carburettor and engine. If that filter gets blocked, your carburettor won’t function properly.
You’ll need to remove the filter and check if it needs cleaning or replacing. Make sure the carburettor hasn’t broken either. Reassemble your mower and check if it works again.
Lawn and Mower Maintenance Tips
Check and maintain your lawn mower regularly – it’ll keep it functional and extend its lifespan. A well-maintained mower will give you the cleanest, neatest cut so your lawn looks pristine throughout the seasons.
Mower will not start? How to diagnose and fix EVERYTHING electrical on a riding mower or zero turn.
Even if you use lawn mowing services. it’s still well worth knowing how to start a lawn mower. You never know when you’ll have to be the one to tackle yard maintenance!
Be thorough when starting your mower, and don’t skip any steps. Safety first is the name of the game – otherwise, you might be Googling “how to fix a busted mower” next.
Jamie Donovan
Jamie is an Australian horticulturalist and landscape designer. He enjoys writing about landscape architecture, garden design and lifestyle topics.
Jamie Donovan
Jamie is an Australian horticulturalist and landscape designer. He enjoys writing about landscape architecture, garden design and lifestyle topics.
The pros and cons of electric lawn mowers
Electric lawn mowers have arrived. We lay out the pros and cons of these green yard machines.
Sean Jackson is a creative copywriter living in Florida. He’s had work published with Realtor.com, theScore, ESPN, and the San Francisco Chronicle. In his free time, Sean likes to play drums, fail miserably at improv and spend time at the beach.
Once upon a time, all lawn mowers were gas-burning beasts whose pull-start motors relied as much on elbow grease as internal combustion just to get started. These days you have more options. While big-box stores still have plenty of gas-powered models on display, there’s a growing number of electric mowers available to purchase.
If you’re new to electric lawn mowers, there are some things you should consider before buying one. Electric mowers certainly offer some unique benefits, but they have some performance limitations you will want to be aware of too.
This guide examines both the benefits and drawbacks of electric mowers. By the time you’re done, you’ll hopefully have a sense of whether or not they’re a suitable fit for your specific lawn care needs.
Pro: Quieter operation
Electric mowers can produce up to 75 decibels (think washing machine volume), whereas gasoline mowers are quite a bit louder at 95 decibels (motorcycle volume). If you live in a suburb, an electric mower will be a less disrupting option for your neighbors.
Pro: Less maintenance
One of the biggest perks of electric mowers is there is less maintenance involved. With gas mowers, you have to replace parts annually. Examples are spark plugs, oil and air filters. That’s not the case with electric mowers. And these savings will increase every year, making an electric model more economical.
Pro: Easier to maneuver
Electric lawn mowers are lighter than their gas powered siblings. That means they’re easier to whip around tight corners and navigate through your yard. For example, the EGO Power Plus 56-Volt 21-in Push Cordless Electric Lawn Mower weighs 62.6 pounds after assembly.
Conversely, gasoline lawn mowers can be much heavier. The Craftsman M250 160-cc 21-in Self-Propelled Gas Push Lawn Mower with Honda Engine weighs a hefty 90 pounds. While the self-propelled engine improves maneuverability when you mow, it is still a heavy object to lug around when it is not in operation.
Pro: Cleaner for the environment
Gasoline-powered mowers emit lots of airborne pollutants. According to the California Air Resources Board, one hour of mowing generates the same pollution as driving a car for 300 miles. Indeed, the Environmental Protection Agency states that gas lawn mowers contribute the lion’s share of nonroad-related air pollution generated nationwide.
A clear clean alternative is the electric lawnmower. The Electric Power Research Institute notes if we replaced half the gas-powered lawn mowers with electric ones, it would reduce the same amount of emissions as removing two million vehicles from the road.
Pro: They can be less expensive
If you are looking to save money, electric lawn mowers might be a wise option to consider. Electric models start as low as 88, the price for the 11-inch, 10-amp Electric Hover Walk Behind Push Mower from Sun Joe. However, this model has a relatively narrow cutting width.
Alternatively, for gas-powered mowers tend to start at around 170. For example, the Yardmax 20-inch 166cc OHV Gas Walk Behind Push Mower and 20-inch 125 cc Briggs Stratton Gas Walk Behind models each cost 169 and cut wider swaths of grass.
So saving a little cash also means you’ll take more time and effort to cut the same area than you would with a bigger mower. Generally, the wider the cutting platform, the more money you’ll pay. For instance, the wider Sun Joe Mow Joe 20-inch model will set you back 170 even though it’s an electric model.
Con: Shorter run times
If your yard is more than half an acre, then an electric model might not be the best choice. Many electric mowers, like the Sun Joe Hover Walk Behind model use a cord. It allows you to mow a yard up to a quarter of an acre. However, that tether can also be a hindrance as you work.
Other electric models run on charged batteries and offer runtimes ranging between 20 and 45 minutes. If it takes longer than this to mow your yard, this limitation is a problem. To finish the job, you’ll have to wait for the mower to recharge. A better solution is to keep another charged battery on hand to extend your mowing time. However, that requires you purchase an extra standalone battery.
Con: Not the best for larger yards
For homeowners with hilly or larger yards, finding the right mower can be a challenge. A riding lawn mower like the gas-powered Toro IronForged Deck Zero Turn Riding Lawn Mower will do the job. It has a huge cutting width of 60 inches and will definitely finish big yards quicker.
You can purchase electric riding mowers as well. The Ryobi 42-inch 75ah Battery Electric Riding Zero Turn Mower offers a decent cutting width of 42 inches. Still, if you have a yard encompassing multiple acres, it will take you longer to finish the job with an electric model like this one.
Con: They are not as powerful
When shopping for a mower, one thing to consider is its torque rating. Torque is the driving force behind a blade’s rotational movement. Electric lawn mowers generate substantially less torque on average than a gas mower does. It means a gas mower will be a much better choice to tackle challenging terrains like hills and dips.
Overall, the lawn mower market continues to expand with diverse offerings. For homeowners with larger yards, gas-powered mowers will still be the best fit, as they have the durability and power to tackle large projects with ease.
Meanwhile, if you want to reduce your carbon footprint, then an electric lawn mower is the wise way to go. Either route you take can help you gain a healthy-looking lawn that boosts the curb appeal and value of your home.
In the meantime, here are some other tips to keep your yard looking great: