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.
Yard machine lawn mower won’t start, how I fixed it.
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.
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.
The Best Self-Propelled Lawn Mowers in 2023 for Making Your Yard Work Easier
These lawn mowers drive themselves, taking the load off you in the process.
By Roy Berendsohn Published: Mar 21, 2023
One of the perks of the warm-weather season is getting to spend time outside. If you own your own home and have a yard, it’s very likely that in order to enjoy your outdoor space, you need to mow the lawn. The larger the yard, the more work it will be to maintain. If you have a lot of grass to cut, you’d be wise to consider a self-propelled lawn mower especially now that there are a ton of sales just in time for Memorial Day.
The primary difference between a standard push mower and a self-propelled mower is that the former moves when you push it, and the latter essentially moves itself with only your guidance. Once the engine is running, all you have to do is squeeze a handle or push a lever and the mower will start moving forward with you as you walk.
Turning the mower around is your job, but once you have your heading, just keep the drive handle squeezed and escort the mower down the path, no pushing necessary.
Self-propelled law mowers take power off the engine and route it via a belt to a pulley on the transmission and axle. When you move the drive control lever on the mower handle, you tension the belt, causing the pulley to turn, and this drives the transmission, moving the mower forward.
Move the drive control lever back and the tension is released, the pulley stops turning, and the mower stops moving forward. The belt-driven transmission is a time-tested design to power the mower and take the load off you in the process.
What to Consider
A mower is like many consumer products in that the more features a manufacturer adds, the more expensive it becomes. But a longer or more eye-catching list of features isn’t necessarily better. Sometimes less is more. Here are the most important to keep in mind.
Front-wheel drive mowers tend to be less expensive than rear-wheel drive units. They can be easier to turn because you don’t have to disengage the drive wheels to do so. Simply push down on the handlebar to raise the front wheels off the ground. However, their traction isn’t as strong on hills or when the bag is full, as there isn’t as much weight over the drive wheels.
Rear-wheel drive mowers do cost more and aren’t as easy to turn, as you do need to disengage the drive—but this isn’t too much of a hassle. Rear-wheel drive mowers shine on hills and inclines, and when the grass bag is full. In either scenario, weight is shifted rearward and over the drive wheels, which enables superior traction, thus making the self-propel more effective.
An engine as small as 125 cc can power a mower, but most are somewhere in the 140 cc to 190 cc range. A large engine helps when powering through tall, lush grass or in extreme conditions, such as with a side discharge chute in place and mowing tall weeds in a border area. Also, the extra torque provided by a larger engine can improve bagging when the going gets tough (tall, leaf-covered grass in the fall). But if you mow sensibly and pay attention to deck height—and especially if you don’t let your lawn get out of control—an engine between 140 and 160 cc has more than enough power to get the job done.
A mower can have all four wheels the same diameter (7 to 8 inches), or it may have rear wheels that range from 9.5 inches to 12 inches in diameter. Larger rear wheels help the mower roll more easily over bumpy ground.
With some mowers you can start the engine with the twist of a key or the press of a button. It’s a great option, but a luxury. Keep the mower engine tuned and use fresh fuel with stabilizer added to it, and you’ll never have trouble starting.
Any number of mechanisms can control a mower’s ground speed—a squeeze handle, a drive bar that you press forward, even a dial. There’s no single right answer here. Look at the design and think about how you like to work. For example, if more than one person will be using the mower (and not all of them are right-handed), a drive control like that on a Toro Personal Pace mower might be the answer. Just push down on the bar to make it go faster. Let up on the bar to slow down.
A mower that can bag, mulch, and side discharge is known as a three-function mower, the most versatile kind. Two-function mowers bag and mulch or mulch and side discharge.
Mowers will typically have one, two, or four levers to control the deck height. Single-lever adjustment is the easiest to use, but it requires more linkage, which adds weight and complexity. If, for some reason, you find yourself varying deck height frequently, it’s a good option. Otherwise, two or four levers work just fine.
Only Honda makes a gas-engine mower with a high-impact plastic deck (there are battery mowers that have plastic decks). Otherwise, mowers generally have a steel deck, and a few manufacturers—Toro, for one—offer a corrosion-resistant aluminum deck. An aluminum deck won’t rot the way a steel deck will, but you still need to keep it clean.
This is a hose fitting mounted on top of the mower’s deck. When you’re done mowing, hook up a hose and run the mower to power wash the underside of the deck. We’ve had mixed results with these, but they’re better than just letting a mass of dried grass clippings accumulate.
expensive mowers come with a more durable bag with more dust-blocking capability. If you bag a lot, especially leaves or other lawn debris in the fall, then you need a mower with a higher quality dust-blocking bag. Having said that, if you rarely bag, the standard one that comes with a mower will last you the life of the mower.
Also called wide-area mowers, machines in this subgroup help homeowners better reconcile their need for more power and speed with the fact that they may not have enough storage for a tractor or zero-turn mower. A typical residential walk mower has a single-blade deck that cuts a swath from 20 to 22 inches wide. Wide-cut mowers (built for homeowner use) have either a single blade or, more typically, a pair of blades, cutting from 26 to 30 inches with each pass. Some of these are rated for light commercial use and have larger decks, in the 32-inch range, and engines that start at 223 cc and go up to about 337 cc.
Wide-cut mowers typically employ gear or hydrostatic drive transmissions, and they have top speeds of about 4 to 6 miles per hour. At their fastest, they move so quickly you have to trot to keep up with them. Needless to say, they’re overkill for small yards; only opt for one of these if you’ve got a significant plot of land that you need to keep tidy, but not one so large that you’d be better off going with a full-on riding mower.
How We Tested and Selected
We compiled this list based on Popular Mechanics mower testing and our knowledge of the lawn mower market at large. For our testing, we put mowers through the paces using our standard Popular Mechanics methodology: We cut turf grasses such as fescues and blue grass and rougher non-turf grasses like Timothy, clover, orchard grass, and wild oats, all in both normal and shin-deep heights. We mow uphill, downhill, and across the faces of hills. The maximum slope we cut is about 30 degrees.
That may not sound like much, but it’s about all you can do to stand on it, let alone push a mower up it or across it. We mow damp and wet grass to test general cutting performance and whether clippings accumulate on the tires. And we cut dry and dusty surfaces to see how well the bag filters under less-than-optimal conditions.
Honda HRN 216VKA
Honda mowers enjoy a sterling reputation. Having tested their walk and self-propelled mowers for the last 30 years, we feel confident that Honda’s entry level mower is a great choice for homeowners looking for power and durability. The HRN features a GCV 170 gas engine that’s built to withstand long hours of operation.
If you do your own maintenance (and most owners who buy this class of product do), you’ll appreciate the easily accessible spark plug and the fuel shutoff valve that enables better winter storage. Close the fuel shutoff and run the mower until it sputters to a halt. This will clear the carburetor of any gasoline, which will prevent the ethanol in it from disintegrating and causing running issues later on. Open the shutoff valve in the spring, add some fresh gasoline, and the mower should start easily.
All this maintenance stuff is great, but we can also tell you that our past test findings on other Hondas prove that their cut quality is outstanding for cleanliness. Sharp blades deliver a velvet-like finish. And their bagging ability is also quite good, in the same league with other well-bagging mowers from Toro.
In all, if you take mowing seriously, you should enjoy this Honda. If you have a little wiggle room in your budget, consider the Honda HRX, which features a mower powerful engine and a composite deck that won’t rust and is renowned for its durability.
One note is that Honda has announced that it will cease selling lawn mowers in the United States after this year—so if you’re considering buying one, best do it sooner rather than later.
Toro Recycler 60-Volt Max Lithium-Ion
Toro mowers have garnered more recommendations from us than any other brand for two reasons: build quality and cut quality. These were amply demonstrated in our testing as the Recycler turned in the best ratio of cut area per amp-hour of battery in the self-propelled category, while at the same time not skimping on cutting, mulching, or bagging quality.
We attribute this outstanding mower performance to three features, all upgrades to the previous version of this machine. First, the air vent at the front of the mower deck seems to improve mulching and bagging performance. Toro calls it Vortex technology, a design that increases air flow under the deck. This helps to stand the grass for a cleaner cut, which improves mulching performance, and also allows better airflow into the bag when collecting the clippings.
Next, the company’s redesigned “Atomic” blade configuration appears to assist the air flow and clipping movement. Finally, the three-phase, 60-volt motor is exceptionally efficient, resulting in a large cut area for a single battery.
Toro has maintained features that make this mower work: rear wheel drive, a one-piece deck that’s all steel (no plastic nose), 11-inch wheels to help it roll over roots and crevices, and the same fold-forward handle that was an industry breakthrough when it was introduced some years ago.
Ryobi 40-Volt Brushless Self-Propelled Mower
This is one of Ryobi’s top-of-the-line mowers, and it’s American-made construction is something we wish we saw more of. It delivers a tremendous cut area with its two 6-Ah batteries providing a total of 12-Ah of capacity, and its X-shaped blade leaves a pristine surface in its wake.
Ryobi estimates the design should provide 70 minutes of run time; we didn’t time our cut, but it strikes as plausible. Its rear-wheel drive and reasonably aggressive tire tread pattern provide good hill climbing and sidehill cutting performance, and its bagging on all surfaces (level, sidehill, and uphill) is also commendable.
Other ease-of-use features include an easily installed or removed bag that mounts and dismounts straight up and down through the handle; deck adjustment is quick and easy thanks to a single-level deck height adjustment. The straight edge deck is polypropylene; it will never rust and needs very little care other than basic cleaning.
Toro TimeMaster 30 in. Briggs Stratton Personal Pace
The Toro Timemaster 30-in. mower has been around for several years and has earned a reputation as a sturdy workhorse for homeowners who want to cut down on their mowing time. It’s also used by some professionals as well. A few years ago the Timemaster got a slightly more powerful Briggs and Stratton gas engine, so it should have no issues powering through most demanding mowing jobs.
The Timemaster is rear-wheel drive and features Toro’s Personal Pace drive system that’s used on many of its self-propelled mowers. This allows the mower to move at your speed by simply pushing down or releasing the handle, which is spring-tensioned.
With a 30-in. deck, Toro claims the Timemaster will help you reduce your mowing time by about 40% compared to using a standard-sized mower. You can mulch, back, or side discharge with the Timemaster, and the handlebar can be locked in a fully vertical position to reduce space consumption in storage.
If you have half an acre to a full acre of lawn to mow and prefer the experience of a walk-behind mower versus a tractor or zero-turn, the Timemaster is worth a look.
Craftsman mowers have been doing very well in our tests, so we can recommend this one because it’s so much like the many other of the brand’s models that we’ve tested. If you’re looking for a good blend of maneuverability and power, you’ll get it with this mower. Its front drive helps move it along and makes it easy to turn.
It’s important to note that front-drive mowers do lose some traction when running uphill, particularly with a full grass bag. But if your slope is less than 20 degrees, and you’re not bagging uphill, you’ll be fine. The side discharge will also help you handle tall grass. Adjust the two deck levers to bring the mower up to full height and have at the rough stuff.
The fact that this mower bags, mulches, and side discharges is a plus, enabling you to handle a wide range of mowing conditions, from early spring and late into the fall. Three-function mowers like this are our preference for that versatility.
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Toro Super Recycler Self-Propelled Lawn Mower
This is a beauty of a mower, with a cast-aluminum deck and a smooth-running Briggs Stratton 163-cc engine. We tested the Honda engine-equipped version, and it was effective at both bagging and mulching, even in moist grass.
Equipped with rear-wheel drive and the Personal Pace system (the farther you push the drive bar, the faster the mower goes), it’s an effective hill climber and moderately effective on sidehill cutting. It has relatively small 7.5-inch tires on all four corners, which causes this Toro to bump up and down a bit on washboard surfaces. But the good news is that it’s equipped with a far higher quality tire than we’re used to seeing these days. We didn’t notice them pick up any grass on moist surfaces.
Other features we like include its forward-fold handle that has a built-in shock absorber that Toro calls a Flex Handle Suspension, and a high-quality grass bag that loads through the handle, from the top.
Are there special maintenance considerations with self-propelled mowers?
Yes. Both front- and rear-wheel drive mowers typically feature a drive belt, which can crack or wear out over time. Fortunately these belts are not difficult or particularly expensive to replace.
Secondly, you may have to replace the drive wheels occasionally. These wheels are driven with gears. there are typically teeth on the inside diameter of the drive wheel that line up with a gear on the axle. These teeth can wear out, especially if they are made of plastic. Higher-end mowers may feature drive wheels with a metal gear that meets the metal axle gear, which improves longevity of these components.
My lawnmower says I don’t ever have to change the oil, but just add oil when needed. Is this OK?
It’s not a good idea to never change the oil in your lawn mower. In a lawn mower, same as a car, oil degrades over time and is less effective at reducing heat and friction in metal components. Changing the oil in your lawn mower is easy to do and will significantly increase its service life. For most homeowners, changing the oil at the beginning or end of each mowing season should be sufficient, though there is certainly no harm in doing it more often.
Roy Berendsohn has worked for more than 25 years at Popular Mechanics, where he has written on carpentry, masonry, painting, plumbing, electrical, woodworking, blacksmithing, welding, lawn care, chainsaw use, and outdoor power equipment. When he’s not working on his own house, he volunteers with Sovereign Grace Church doing home repair for families in rural, suburban and urban locations throughout central and southern New Jersey.