Petrol lawnmower spark plug. Mower Won’t Start No Spark (This Is Why)
Mower Won’t Start No Spark (This Is Why)
Pulling and pulling and nothing, a mower without spark, is useless. In this post, we’ll cover all the most common ignition system failures.
Mower won’t start any spark? Common reasons a lawnmower has no spark include:
None of these tests are difficult, and twenty minutes from now, you’ll know why your mower has no spark.This post will have you covered, but if you need video help diagnosing no spark or help to fit a new coil, check out “Mower won’t start video.”
Checking Lawnmower Spark
Since you’ve checked the spark already, I’m guessing you know the procedure. However, it’s worth pointing out, getting this test wrong can lead to misdiagnosing and replacing the ignition coil or other parts unnecessarily.
Spark testing is, as you know, a simple test, you won’t need any special tools here, but a spark testing tool does make the job easier and totally foolproof.
If you need video help, check out the mower “Mower spark test video,” where I cover the whole process.
Tools needed
For these tests, you’ll need a plug spanner, insulated pliers, screwdrivers, and a spark plug is useful. You’ll also need a helper, as we’re not using a spark testing tool. It can be difficult to crank over the engine and, at the same time, check for spark. With all the tools gathered and a helper on hand, we’ll get right to it.
Spark Testing
As we’ll have a helper cranking over the engine, that means the blade will be spinning, and even though the engine’s not running, it can still remove body parts, so, you know!
You must use insulated pliers (plastic/rubber-handled pliers) to hold the plug as the voltages produced are enough to give you a jolt, which isn’t pleasant.
Tools – Plug spanner, insulated pliers, and a spark plug will be needed.
Spark test tools
Step 1 – Remove the spark plug wire by twisting and pulling, then using the plug tool, remove the spark plug.
Step 2 – Reattach the spark plug wire to the plug. Using your insulated pliers, hold the plug threads firmly against the metal of the engine. This is known as grounding. If the plug doesn’t make good contact with the metal of the engine, you won’t get a spark.
Step 3 – While you watch for spark, have the helper hold the bail lever as normal and yank on the pull cord.
If you have no spark, swap out the plug and test again.
If you still have no spark, it is most likely a failed coil, but best to check the on/off switch assembly first.
Common Spark Plug Faults
A healthy spark plug is essential for reliability, power, and smooth running. Plugs have a tough job. They carry high voltages and live at the heart of the engine where it’s hottest.
Making matters worse for the plug is its location – right out front of the engine. So getting shoved into fences and trees is all part of a spark plug’s life, and you thought you had it hard!These are the most common spark plug faults:
- Wrong plug type
- Dirty plug
- Bad plug gap
- Cracked spark plug insulator
Wrong Plug Type
Plugs areas you know are graded; each engine will have a particular plug code. So even though a plug fits, it doesn’t mean it’s correct. Plugs are graded by heat. The plug should get hot enough to burn off contaminants but not so hot that it pre-ignites. Wrong plug types can cause all types of problems, from hard starting, rough running, hot start failures, etc.
Plug type – Check your plug type with your mower engine maker.
An incorrect plug type will lead to intermittent problems.
Dirty Plug
Self-explanatory, it’s a plug that’s contaminated by too much gas (flooding), carbon, or oil. All of these will prevent the plug from doing its job. Flooding may be caused for a few reasons – blocked air filter, faulty choke, overuse of choke, tipping mower over on its carburetor side, and carburetor fault. Check out the video “How to fix a flooded engine.”
Carbon build-up in the engine is a normal condition. Fuel type, oil type, maintenance, and plug type all affect how quickly it builds.
Oil on the plug is also common. It’s caused by too much oil, blocked crankcase breather, head gasket fault, engine wear, and wrong plug type. Check out the video “How to clean a plug.”
Bad Plug Gap
A spark plug function is obviously to create a spark, and it can only do this if the electrode gap is correct. The coil has been designed to create a sufficient spark to jump a pre-determined spark plug gap.
- No gap, means no spark
- Gap too small means poor running or no start
- Gap too big means no start and risks damaging the coil
A plug gap tool is used to set the spark plugs gap. The electrode is manipulated to the correct size by simply bending it with pliers. Check out the video “How to gap a plug.”
Plug gap – The gap is important. Too small or too big can lead to no starts or poor running.
Cracked Plug Insulator
Self-explanatory too. The insulator is the white ceramic material of the plug’s body, and as said earlier, plugs are at risk of being damaged by bumping into obstacles. If the insulator breaks or cracks, the plug stops working.
Common Spark Plug Wire Faults
A spark plug wire has a few particular problems that affect them, depending on a few variables, like how and where they’re stored.
The common faults I see again and again include:
Loose Terminal
Caused by our old friends, the trees, shrubs, and fences. The plug wire terminal that clips to the spark plug becomes loose, and that can cause no starts, poor running, and intermittent starting/running.The fix here is simple, squeeze the terminal body using pliers to tighten it.
A loose terminal will cause the engine to misfire or not start at all. The quick fix here is to squeeze the terminal until it fits snugly on the plug.
Faulty Terminal
Because this cap was loose, it created arching, which burnt the metal of the terminal cap.
Faulty terminal connector – It’s different but related to a loose connector. A loose connector will often turn into a faulty one as the spark starts to jump inside the terminal, burning it or setting up conditions for corrosion to take hold.
The outcome is the same, no spark or poor running. A replacement terminal can be purchased and fitted to solve this issue.
Damaged Plug Wire
Plug wire rubbing off the engine cover can cause the insulation to wear and the coil to ground. But more often than not, a damaged plug wire means rodents. Mice love wiring insulation, and unfortunately, our furry friends have cost us a coil.
Sure, you can wrap them with insulation tape, but it’s only a quick fix. The long-term repair is to replace.
Damaged wire – Mice love to chew on the wiring insulation.
Common Stop/StartAssembly Faults
Most mower owners are familiar with the bail lever at the handlebars, which must be held to start the mower. Most mowers will use this type of stop/start system; other manufacturers may incorporate the stop/start function with the throttle lever. But apart from this difference, all other components will be very similar.
The main components of the stop/start assembly include:
No fire? No Spark? CHECK THIS FIRST How to make sure your ignition module is BAD on ANY small engine
- Bail/throttle lever
- Cable
- Flywheel brake assembly
- Stop/start switch
- Coil control wire
Bail / Throttle Lever
Common faults here include disconnected, out of adjustment, or broken levers.
Cable
The cables break and stretch, so it’s not uncommon for the bail lever to work, but because the cable has stretched, it doesn’t move the brake assembly to the start position.
Stop / start cable
Flywheel Brake Assembly
Common faults here include cable out of adjustment, meaning the bail lever doesn’t pull the brake to the off position.
Flywheel assembly
Stop/Start Switch
This is the on/off switch. It’s fitted at the flywheel brake assembly. When the bail lever pulls the assembly, it pushes on the switch removing the ground connection to the coil. This allows the mower to start.
On /off switch
Coil control – Here’s a different mower coil control switch. It’s a very simple connection; the contact points must separate before the coil and plug will create a spark.
The Coil (also known as Armature)
The control wire is connected from the stop/start switch on the flywheel brake assembly to the coil, which is fitted to the engine. The coil and plug won’t produce a spark so long as the control wire is connected to the ground (Metal of the engine).
A common fault is the chafing of the control wire on the engine (shorting to the ground); this effect is the same as releasing the bail lever – turns the engine off.
Check coil control wire for chafing, especially anywhere the wiring turns sharply around the engine.
Coil control wire – Coil control is a single wire with a push-on connection. Often they’ll come loose, and when they do, the mower won’t turn off.
Common Coil Faults
Coils generally work, or they don’t. Occasionally, you’ll get a coil that works when it’s cold and stops when the engine heats up. Coils are solid-state units – they can’t be repaired. Testing a coil and fitting a new one is easy; I wrote a whole post about it right here “Push mower hard to start when hot”.
Or check out the video here; it covers spark checking, diagnosing, and replacing the coil. If you need to replace the coil, check out the great deals on the Amazon link below.
Coils – Lawnmower coils give lots of problems; I replace tons of them.
Related Questions
Can a spark plug have a bad spark? Spark plugs wear out. A spark plug should be changed once every year at the start of the new season. You can check the spark plug for spark by removing it, connecting the plug wire, grounding it off the engine, and turning over the engine.
Hey, I’m John, and I’m a Red Seal Qualified Service Technician with over twenty-five years experience.
I’ve worked on all types of mechanical equipment, from cars to grass machinery, and this site is where I share fluff-free hacks, tips, and insider know-how.
And the best part. it’s free!
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.
Why A Petrol Lawnmower Has No Spark
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
Key Specs
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
Key Specs
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
Key Specs
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 M220
Key Specs
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.
Toro Super Recycler Self-Propelled Lawn Mower
Key Specs
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.
QA
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.
Why Is My Lawn Mower Spark Plug Wet? (And How Can I Fix It?)
So you are here because you are asking why is my lawn mower spark plug wet?
It is a valid concern, as these small pieces of equipment are what essentially make your mower’s engine produce power by supplying the spark to ignite the mix of air and fuel.
If the spark plug is wet then it makes doing this A LOT harder!
Let’s take a look at what can cause a wet spark plug and how to fix.
Why Is My Lawn Mower Spark Plug Wet?
If your lawn mower spark plug is wet, then it will nearly always be wet with oil or without petrol. If it is wet with petrol it is often because either you have flooded the engine when trying to start it, or too much fuel is being allowed in the carburetor. If it is wet with oil usually either the tank has been overfilled, oil has leaked onto the plugs when it has been tilted or the piston seals are worn.
What Are the Symptoms of Wet Spark Plugs?
Let’s ignore the most obvious symptom of a wet spark plug for now (it feels wet…).
Beyond physically looking at, and touching the spark plug, there are a few telltale signs that there is an issue with your lawn mower’s spark plug:
- Your Mower Is Difficult to StartThis is the most common symptom of a faulty spark plug. It isn’t properly producing the spark to ignite the air/fuel mixture and start the engine. It might take several pulls on the starter rope or turns of the engine to get your mower going.
- Your Mower Isn’t Running ProperlyWe can all immediately tell when any piece of mechanical machinery isn’t performing to its optimum levels. It might keep dying out, spluttering or faltering. This could be because a faulty spark plug is causing the engine to misfire.
- Your Mower is Consuming a Lot of FuelWhen a spark plug is faulty the fuel is not being burnt properly, thus the mower is less efficient and fuel consumption is higher. Often the fuel will emit an unusual odor as well.
If you notice your spark plug is wet, then it stands to reason that it will have been made wet by one of two substances…
Why Is My Spark Plug Wet With Petrol?
If you are finding the spark plug on your lawn mower is wet with petrol, there are two possible explanations.
Reason #1: You Have Flooded the Engine by Excessive Use of the Choke
Overly using the choke when starting your mower will flood the engine with too much fuel and not enough air.
The plug will become fuel fouled as a result and not spark.
How to Fix This
If this is the problem you can either:
- Remove the spark plug. Pull the starter cord a few times to get rid of any fuel from the cylinder. Reinstall the spark plug when it has dried out.
- Remove the air filter and put some starter fluid into the mouth of the carburetor. The starter fluid should get the engine going, and then combustion process should dry the spark plug.
Reason #2: There Could Be a Problem With the Carburetor
If the above doesn’t appear to be the issue, then there could be a problem with the carburetor.
Often the cause here is linked to the carburetor float needle and seat. They might be worn out, the fuel float could be leaky, or something (such as dirt) could be holding the needle off its seat.
What then happens is too much fuel enters the float chamber and is passed into the carburetor.
Air pressure forces excessive fuel into the engine flooding the spark plug.
How to Fix This
If it is severely clogged, then sufficient amounts of air cannot enter the carburetor, which is then flooded by too much fuel.
Also refer back to the owner’s manual. Often failing to follow the correct procedure when starting the mower can be to blame.
#2: Why Is My Spark Plug Wet With Oil?
The other substance your spark plug is likely to be wet with is oil.
Usually, this will be due to one of three reasons.
Reason #1: The Tank Has Been Overfilled With Oil
If too much oil is poured into the tank, the crankcase can overflow, and the oil will leak onto the spark plug.
How to Fix This
Simply remove the oil cap and drain out some of the oil. The best way to do this is to use something like a turkey baster and extract the excess oil this way.
Reason #2: The Mower Has Been Tipped on its Side
Have you recently tilted your mower sideways to clean under the deck or sharpen the blades maybe?
If so, when you did this oil may have pooled up under the piston and either seeped past the piston rings or entered the carburetor via the air intake when the mower was turned on. From there this can cause the spark plug electrodes to become oily.
How to Fix This
You can remove the spark plug and allow it to dry, or clean it with carburetor or brake cleaner.
When you reinstall the plug the engine should dry out any remaining oil on the spark plug.
Reason #3: The Piston Ring Seals Are Worn
The seals on piston rings prevent oil from leaking into the combustion chamber.
If they become too worn, oil can spray onto the spark plug.
How to Fix This
Piston ring wear occurs when there has been excessive use of the engine. It isn’t an easy part to replace and will require an engine rebuild.
If you are mechanically minded you can try and replace the piston rings, but often it is easier and sometimes cheaper to buy a new mower.
Or if the mower is still running fine you can continue to use it.
Wet Spark Plugs and Two-Cycle Engines
Although most mowers these days are four-cycle, there are still some two-cycle mowers knocking about.
If you have a two-cycle engine, then a wet spark plug isn’t actually too much to worry about, in fact it is somewhat normal.
With two-stroke engines, there is always a bit of oil residue in the cylinder, and often this will make its way onto the spark plug.
The mix of fuel and oil that two-stroke engines burn is meant to leave a bit of oil behind as a lubricant.
Lots of excess oil in the cylinder of a two-stroke mower might indicate that you have added too much oil to your fuel.
How to Fix Wet Spark Plugs: An Overview
If you are having trouble starting or keeping your lawn mower running then there could be an issue with the spark plugs.
If they are wet then they won’t ignite properly.
Whilst sometimes water in the tank or injector leaks can be the cause of a wet lawn mower spark plug, this is very rare.
It will nearly always be wet with oil or with petrol.
Most of the time the problem can be fixed without a huge amount of expense. The exception to this rule is if the cause is worn piston rings.
But even then most lawn mower engines are built to last at least five years, so if your piston rings are worn you should hopefully have got plenty of use out of them by this point.
Why The Spark Plug of The Lawn Mower is Wet? How To Fix It?
Have you ever experienced a wet spark plug of your lawnmower? Sometimes, it occurs when the spark plug comes in contact with gas or oil. In this post, we are going to reveal the reason behind a wet spark plug of your lawnmower.
Why is lawn mower spark plug wet?
Wet spark plugs in lawnmowers can occur for several reasons. According to experts, the most common reason is that the spark becomes excessively hot due to the inclusion of ethanol in the gas.
And, there is a flood of oil in the combustion chamber or, the engine is flooded with water/fuel.
Why Is Lawn Mower Spark Plug Wet?
Spark plugs can become wet on a lawn mower for a variety of reasons. When the spark plug gets wet, you need to either clean it correctly or replace it with a new one.
But before cleaning or replacing it, first, you should know why your lawn mower spark plug is wet. Like other moving parts of lawn mower, spark plugs wear out eventually, leading to malfunction.
Engine Flooding
When you often had to try several times to start your lawn mower, it is an early indication of wet spark plugs. Trying this multiple times may lead to engine flooding, which ultimately drenches the spark plug. As a result, the engine is failing to generate any sparks and can’t start the engine.
So, why engine flooding occurs in lawn mower spark plug?
Your spark plug may encounter this issue during freezing weather conditions. In order to ignite the lawn mower engine with previously worn or fouled spark plugs, a higher voltage is required.
Under these circumstances, you should either let the plug becomes dry or take it off from the mower and clean it.
Injector Leaks
Though wet fouling is rare among the latest lawn mower engines, some mechanical problems can occur. Leaking cold start injector is one of the most common issues your engine may encounter.
When this happens, the engine compartment will likely be filled with a rich starting mixture, ultimately leading the spark plug to foul.
Worn Piston Rings
A study done by Mopar Magazine reported that fouling might occur when piston rings or cylinders are worn out in older lawn mower engines.
As a result, you may notice your lower mower engine is flooded with gasoline or too much oil. In addition, an ignition attempt may not be successful if a spark does not form.
In this condition, you can easily handle the spark plug by removing and cleaning it properly and then re-install it in the place where it should be.
Why My Lawn Mower Spark Plug Wet With Gas?
The main job of an electrical device like a spark plug is to source power to start your lawn mower. You always want to keep this electric device away from getting wet to perform consistently for generating sparks. However, it may often get soaked with gas or gasoline, leading to a flooded engine.
Why is my lawn mower spark plug wet with gas?
If a lawn mower spark plug becomes wet with gas, it can happen for multiple reasons such as lousy ignition cable, or engine flooding, or internal crack in the ceramic insulator, or dirt or moisture on the outside of the plug.
When spark plugs get wet with gas, it means the electrodes have not been ignited. If it happens due to a bad ignition cable, the components are unable to carry an appropriate amount of current under heavy load conditions. So, these are the reasons behind a lawn mower spark plug wet with gas.
Why My Lawn Mower Spark Plug Wet With Oil?
By looking at the spark plugs tips and other sports, you can have an idea about its health conditions and how well the engine can perform. You can also get an idea about other problems based on the appearance and color of the deposits.
Why is my lawn mower spark plug wet with oil?
If the spark plug is becoming excessively hot and the chamber is filled with oil, you may struggle to run the mower. There can be different reasons behind lawn mower spark plug wet with oil, such as using a spark plug for too long, excessive choke usage, or stucking issue with the float.
Using A Spark A Plug For Too Long
According to experts, a spark plug needs to be replaced or changed on average after two years. If you use your lawn mower heavily, you may need to replace it earlier.
Excessive Usage Of The Choke
There’s a possibility you have to exceed the choke usage, resulting in excessive fuel in the system. Also, make sure you don’t over-prime your mower as a primer is designed to improve combustion and freshen up gas.
Stucking Issue With The Float
An automatic liquid supply system runs efficiently with a float chamber, which controls the fuel delivered to the system. When the float fails to control the amount of fuel delivered, it may make the spark plug wet with oil.
What Causes A Spark Plug To Become Wet With Fuel On A Lawn Mower Engine?
It is called “fuel fouling” when the lawn mower’s spark plug becomes wet with fuel. A spark plug wet with fuel may prevent you from running the machine smoothly, and you may fail to cut the grass efficiently.
What causes a spark plug to become wet with fuel on a lawn mower engine?
One reason can be to adjust the throttle too aggressively or too tightly, which prevents the plug from having sufficient air. Or, you may have spilled fuel while the spark plug is seated beneath the fuel tank.
Until you repair the carburetor, turn off the fuel tap. You need to clean it to prevent fuel from leaking into the engine overnight. However, it is best to turn it off after you mow the lawn. Knowing what causes a spark plug to become wet with fuel on a lawn mower engine helps you treat the machine effectively.
What Happens If a Spark Plug Gets Wet?
Engine flooding is one of the most common issues you will notice for wet spark plugs. You flood your lawn mower engine when you try to start it more than once without getting a response.
What happens if a spark plug gets wet?
When the spark plug of your lawn mower gets wet, it is highly likely to misfire. As a result, the current typically flows over an insulator as the gas/oil/fuel conducts it instead of passing through the gap.
Knowing what happens if a spark plug gets wet helps you take preventive measures so that your lawn mower becomes excessively damage. You can improve the life of the lawn mower if you take precautions sooner.
What Happens If Water Gets In Spark Plug?
When your spark plug gets wet with water, it will hinder the engine’s ability to start. Though cleaning is the best solution to eliminate this problem, there is no guarantee the problem won’t come back.
What happens if water gets in spark plug?
When water gets in your lawn mower spark plug, it gets wet. Additionally, the spark plug has the probability of getting a cracked head or blown head in the future. Most importantly, it will make the machine suddenly stop or firing inappropriately while mowing.
However, it is essential to note if the spark plug has water only on the outside surface. You won’t notice many problems until there is a loose fit between the boots and the plug body.
Should I Fix it Myself, or Take it to a Technician?
If you are already familiar with machine repair work, you can do it on your own. However, first of all, you want to figure out the actual problem of your spark plug and the best way to fix it.
You can take suggestions from a nearby local store or get some instructions for fixing it online. This could save you few bucks than hiring a professional.
However, it is well appreciated to take the spark plug to the nearby local store as they have all the necessary equipment and are professional to fix it quickly.
Tips To Prevent Wet Spark Plugs
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Conclusion
So have you found the answer to this golden question: why is lawn mower spark plug wet? Surely, you need it! So take care of your lawn mower properly to ensure the best possible lifespan.
Last update on 2023-01-28 / Affiliate links / Images from Amazon Product Advertising API
Lee Safin was born near Sacramento, California on a prune growing farm. His parents were immigrants from Russia who had fled the Bolshevik Revolution. They were determined to give their children a better life than they had known. Education was the key for Lee and his siblings, so they could make their own way in the world. Lee attended five universities, where he studied plant sciences and soil technologies. He also has many years of experience in the U.S. Department of Agriculture as a commercial fertilizer formulator.