My Lawn Mower is Not Getting Gas to Spark Plug [5 Fixes that Work]
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It is frustrating when your lawn mower won’t start. I’ve seen this problem even with new gas-powered mowers. After extensive diagnosis and experience, I’ve found the most common cause is that the lawn mower is not getting gas to the spark plug. But that’s not all.
When your lawn mower won’t start, chances are it is not getting gas to the spark plug. Common causes include a dirty air filter, spark plug, and carburetor. To fix these issues, replace the fuel filter, clean the carburetor and spark plug, and replace the fuel if it is old as illustrated below.
What causes my lawn mower not to pump gas to spark plugs?
Gas-powered lawn mowers need gas to be pumped into the carburetor in order to start. Should anything obstruct the flow of gasoline, the engine won’t start. And even if it does, it’s likely to fail after a couple of minutes.
Here’s what causes mowers to not efficiently pump gas to the spark plug and ignite:
A dirty air filter
The air filter on a carburetor cleans the incoming air of dust and other debris that could cause damage to engine parts. Over time, the air filter could get clogged up, thus affecting the flow of oxygen to the engine.
When the engine does not get enough oxygen that helps with fuel combustion when the spark plug ignites your lawn mower won’t start.
Manual choke left turned on
The choke is a shaft-mounted valve within the air intake chamber of the carburetor. Its function is to block the airflow for improved suction and consequently facilitate a more efficient engine start-up.
While some chokes are automatic, some mower motors have manual chokes that the user has to turn on and off by themselves.
If you leave a manual choke on several minutes after starting the mower, the carburetor will likely flood up, leading to starting failures the next time you try to start up your lawn mower.
Clogged filters in the fuel pump
powerful mowers, such as ride-along lawn mowers, make use of fuel pumps to pump gas into the engine – instead of the gravity-feeding system that’s common in most push-along mowers.
If the filters are clogged, your lawn mower won’t start because gas will not reach the spark plug.
Stuck open valves
If the intake and exhaust valves don’t seal fully due to sticking, build-up of debris or normal wear and tear, compression is hampered, consequently creating ignition problems.
If the intake valve becomes stuck, this affects the efficiency of the flow of the air/fuel mixture to the cylinder, resulting in a lawn mower that won’t start.
Signs your lawn mower is not getting gas
There are several issues that could be causing your lawn mower not to run, including electric faults within the spark plugs as well as the causes I’ve listed above.
For instance- if your spark plug is wet, you definitely can’t get your motor to start. However- more often than not- the issue is usually caused by the cutting off of efficient fuel supply to the spark plugs.
Here are a few signs your lawn mower is not getting gas to the spark plug and won’t start due to the inability to pump gas to the engine:
Lawn mower won’t start completely
If you totally can’t get your mower to start, there could be issues with the efficiency of fuel flow to the engine.
- This is usually caused by debris collecting and blocking crucial components of the fuel intake system such as the throttle, primer button, carburetor bowl, and the fuel filter.
- A malfunctioned fuel pump.
Such clogging hampers the efficient flow of gas to the spark plugs.
Riding lawn mower starts then stops running
If your fuel tank is full, but your mower still comes to a stop after just a few seconds, it’s highly likely that the hole atop the tank’s cap has been blocked by dust and debris.
This cuts off the back pressure needed to push fuel out of the tank and into the carburetor – by cutting off air supply into the tank.
How To FIX a TROY BILT Lawnmower HONDA Engine WILL NOT START, STARTS then DIES. WATER in GAS
No gasoline odor
If you can’t get your mower to start and at the same time can’t sense any gas smell coming from the motor, your lawnmower has definitely run out of fuel.
Most mower brands typically include a dipstick attached to the screw cap. A dipstick is used to check the fuel level within the gas tank. It will typically have low and high-level markers.
- Dip the dipstick into the gas tank to check the gasoline level.
- If the fuel mark is below the low-level mark, it means you’re running out of gasoline and that’s why your mower won’t start.
In this case, refill the gas tank then try starting the mower again to see if the problem will have been fixed.
See also my guide on the type of gas to use with your lawn mower
How to Fix a Lawn Mower that’s Not Getting Gas
Some of these problems can occur when in the middle of mowing. A dirty spark plug, for instance, may cause your lawn mower not to have enough power for mowing. Fuel pump and filter problems too can make it not to start.
Here are simple DIY fixes you can use to correct the problem and start the lawn mower again.
Use fresh or new fuel
I found that for Craftsman mowers, old fuel tends to clog up the carburetors and cause difficulty in the flow of gasoline. As such, you should always ensure that the gasoline in your tank is as fresh as necessary.
- A good way of keeping stored oil fresher for longer is to use a gas stabilization product.
- Use a high-quality fuel stabilizer for small engines such as the Star Tron Enzyme Fuel Treatment.
This solution will prevent fuel degradation by reducing oxidation. Your fuel will stay clean and fresh for longer.
Replace the fuel filter
If you own a Husqvarna mower and it won’t start, the most likely cause would be a clogged fuel filter. This usually happens if you’ve left fuel in your mower for long.
The best fix is to drain off the old fuel from the gas tank and replacing the filter.
Clean the carburetor
For MTD mowers, the most common cause of fuel not getting to the spark plug is a clogged-up carburetor due to the buildup of debris.
To fix the problem, clean up the carburetor by taking out the fuel bowl and spraying the carburetor with some carburetor cleaner.
A clean carburetor will get your MTD lawn mower motor running again.
Here’s a video on how to clean the carburetor on your lawn mower:
Lawn Mower Starts With Starter Fluid Then Dies: Fixes
It becomes worrying when your lawn mower starts with starter fluid then dies. especially if you think that getting your lawn mower to start using a starter fluid might do the trick. Problems related to the air filter, carburetor, spark plugs, fuel, fuel cap, and oil are the most common causes that make your mower suffer from this malfunction.
Given that there are plenty of things to consider when diagnosing the issue, we will help you in this article by covering the possible problems in detail and then aiding you in troubleshooting this issue by providing the solutions needed for you to fix it.
- Why Does Your Lawn Mower Starts With Starter Fluid Then Dies?
- – Clogged or Dirty Air Filter
- – Carburetor Issue
- – Old Gas
- – Defective or Dirty Spark Plug
- – Oil Level Issue
- – Blocked Fuel Cap
- – Clean or Replace the Air Filter
- – Remove and Replace the Fuel
- – Change the Spark Plug
- – Fix the Oil Level
- – Clean the Fuel Cap
Why Does Your Lawn Mower Starts With Starter Fluid Then Dies?
Your lawn mower starts with starter fluid then dies because of a clogged or dirty air filter, a carburetor issue, old gas, a defective or dirty spark plug, oil level issues, or a blocked fuel cap.
It is important to identify the root cause before administering a solution.
Here are the common reasons why your engine only starts with starter fluid then dies, let’s begin to tackle them one by one and discover what is really happening with your lawn mower.
– Clogged or Dirty Air Filter
Issues with the air filter commonly cause a lot of different troubles for lawn mowers. However, this issue is not difficult to identify. Having a dirty or clogged air filter will result in an inadequate amount of air that can enter the engine, such that your mower won’t start.
Commonly, air filters can be clogged by oil due to incorrect tilting of the lawn mower or when your mower is filled with dirt and debris that have accumulated over time.
– Carburetor Issue
One of the common reasons why a small engine turns over when you are using a starting fluid and then dies is a fuel supply-related issue. However, this is not uncommon. What is really happening is that the starter fluid is enough that your lawn mower starts at first, but since the carburetor is not supplying the right ratio of air and fuel, the engine suddenly stops after a while.
So, issues that have to do with a dirty carburetor can be considered as one of the culprits. This happens when your lawn mower is not used often and is allowed to stay running for a long time. When this happens, the gas in the bowl of the carburetor becomes gunk over time.
– Old Gas
When old fuel turns to gunk in the carburetor, the same thing happens in the fuel tank. Though not all types of gas easily turn bad as time goes by, it is recommended to add a fuel stabilizer to prevent your fuel from getting old and going bad for a longer period of time.
Keep in mind that you should always check the carburetor and the fuel before using the lawn mower. especially if you had not used the machine for a couple of years.
– Defective or Dirty Spark Plug
If you have already checked the fuel and the carburetor and both turned out fine, then maybe those problems are not related to the gas supply but rather in igniting the gas. So this is the time when you have to look at the spark plugs.
There are a lot of reasons why spark plugs cause issues, but if your engine starts with starter fluid then dies. a faint spark is probably the reason. You can easily inspect the spark plug and replace it once you ensure that it is already damaged. If not, you can give it a good cleaning if dirt has already accumulated on it.
– Oil Level Issue
Another thing you could check is the oil level. You can use a dipstick to do this. Alternatively, you can observe whether your mower releases white smoke if you try to turn the engine over.
This white smoke could mean that there is oil that is burning in the mower engine. In contrast, if you own a two-cycle mower, observe if there is unburned gas that is released when you try to start the engine.
– Blocked Fuel Cap
The carburetor bowl has a screw placed on its feet that has a narrow opening that supports the bowl. This hole has a chance of getting clogged up and can be a reason why your engine start with a lawn mower starter fluid then dies.
How Can You Fix Your Lawn Mower Starts With Starter Fluid Then Dies?
To fix your lawn mower starts with starter fluid then dies, you can try cleaning or replacing the dirty air filter, removing and replacing the old fuel, changing the spark plug, fixing the oil level, or cleaning the dirty fuel cap.
Upon knowing the possible issues that your lawn mower might be having, let us now discuss how we can fix it through the list below.
– Clean or Replace the Air Filter
Replacing the air filter is the easiest thing to do and won’t take too much of your time, so if this is causing the issue with your mower, consider yourself a bit lucky. First, you have to closely examine your air filter. From there, you could tell if it needs replacement or just a good cleaning. Replace it once it is already full of oil and if there is too much gunk there.
Doing this step may sound difficult and complicated, but surprisingly, it’s not. You can use a carburetor cleaner. Use one with a narrow straw in it to easily spray it exactly on the area where you want it.
After that, remove the air filter, set it aside, and then you will see the air intake. Put the carburetor cleaner there as this will be drawn into the carburetor by the time you try to start the engine, and it may clean off some of the dirt buildup.
Reattach the air filter and then you can turn over the engine. If this method did not work, you can detach the carburetor and give the jets and bowls a good cleaning. However, if you are unsure, you may contact a small engine specialist.
– Remove and Replace the Fuel
If your mower has sat for a long time without running, the fuel may have aged and is no longer as good as it was before. Inspect the gas in the tank, and observe its color. A dark-colored fuel might mean it has already gone bad. The smell should not be pungent or sour and instead should be a normal fuel smell.
Lastly, inspect the fuel closely to see if there are any particles that are floating in it because that will determine that it is not good. If this is the case, you have to remove the bad fuel by draining it out completely using a siphon and replacing it with fresh gas.
– Change the Spark Plug
In order to inspect and replace the spark plug, you have to remove a few parts to get into it. First, unscrew the wirings of the spark plug then observe the electrode and inspect it if it is filled with oil or fuel or has turned black due to carbon. Clean it if it is not extremely dirty or damaged like having cracks on it.
If it is too dirty or damaged, it is recommended that you simply replace it as part of your lawn mower’s maintenance. Also, it is not really that expensive. After getting the newly cleaned or brand-new spark plug, reattach it to the mower, along with the other parts that you have removed at the beginning. After this, you can do a test run.
– Fix the Oil Level
If you find out that your mower has a low oil level, top up the oil to the approved level. In contrast, if your mower has a high oil level, drain the excess off and try to measure it again.
If you own a two-cycle mower and you would not be able to inspect the oil range but think that you might have a higher level than the recommended, you can drain the gas, create a new oil or gas mixture, and finally refill it to the tank.
The bottom line is that proper oil level is crucial, so you should know how to identify the signs and symptoms of a lawn mower having low oil levels.
– Clean the Fuel Cap
When you have a clogged or a dirty fuel cap, cleaning it is the best thing you can do. Sprinkle the crevice with carburetor cleaner and reattach the carburetor bowl carefully to avoid a misshapen fuel cap.
A lawn mower that starts with a starter fluid then dies might mean that there are problems going on inside the engine, but keep in mind that this issue can be fixed easily with the key points from the article:
- A lawn mower that will start with starter fluid and then dies likely has a fuel supply-related issue.
- You can also take a close look at the air filter, fuel, oil, and spark plug to see if the carburetor is perfectly fine.
- Maintaining the cleanliness of the air filter, fuel cap, and sparkplug can save you a lot of trouble by preventing this issue.
- Oil levels should be monitored to avoid mishaps.
- Inspect every part of your mower, especially the fuel and the carburetor, if you haven’t used it in a while.
There are no problems that cannot be fixed when it comes to a lawn mower. Having it diagnosed properly and applying the right method to fix it would do the trick.
Lawnmower Won’t Start? Do this.
A lawnmower that won’t start, especially when taken from storage, is almost always due to one problem: bad gas.
Storing a lawnmower in the fall without adding gasoline stabilizer to the fuel tank can cause the fuel to break down and plug the fuel passages. If fixing that problem doesn’t help, there are a few others that can help fix a lawnmower that won’t start, as we explain here.
How to Fix a Lawnmower That Won’t Start
Replace the Bad Gas
Over time (like the six months your lawnmower sat in your garage over the winter), the lighter hydrocarbons in gas can evaporate. This process creates gums and varnish that dirty the carburetor, plug fuel passages and prevent gas from flowing into the combustion chamber.
The carburetor bowl below formed corrosion and deposits during storage, which can easily plug fuel passages and prevent the engine from starting.
Storing equipment without stabilizing the gas can lead to deposits that foul the carburetor or injectors.
Ethanol-containing gas can absorb water from the atmosphere, which can lead to phase separation, which occurs when ethanol and gas separate, much like oil and water. Ethanol that has absorbed enough moisture and has sat long enough can foul the fuel system and prevent the engine from starting.
No matter how many times you yank the pull cord and pollute the air with your advanced vocabulary, the lawnmower won’t start if it’s trying to run on bad gas.
In extreme cases, evaporation of lighter hydrocarbons can change the gasoline’s composition enough to prevent it from igniting. The gas may be fueling the engine, but it doesn’t matter if it won’t ignite.
Bad Gas in Your Lawnmower? Here’s How to Fix It
If you neglected to add gasoline stabilizer to the fuel prior to storage, empty the tank and replace with fresh gas. If the tank is nearly empty, simply topping off with fresh gas is often enough to get it started.
On some mowers, you can easily remove and empty the fuel tank. Sometimes that’s more trouble than it’s worth. In these cases, use a fluid extraction pump or even a turkey baster to remove the bad gas. You don’t need to remove all of it; but try to get as much out as possible.
Clean the Carburetor
You’ve replaced the fuel, but your lawnmower still won’t start.
Next, try cleaning the carburetor. Remove the air filter and spray carburetor cleaner into the intake. Let it sit for several minutes to help loosen and dissolve varnish and gums.
Remove the air filter and spray carburetor cleaner into the intake. Let it sit a few minutes to loosen deposits.
On some carburetors, you can easily remove the float bowl. If equipped, first remove the small drain plug and drain the gas from the bowl. Remove the float bowl cover and spray the float and narrow fuel passages with carburetor cleaner.
This kind of “quick-and-dirty” carburetor cleaning is usually all it takes to get the gas flowing again and your lawnmower back to cutting grass.
If not, consider removing the carburetor from the engine, disassembling it and giving it a good cleaning. Be forewarned, however: taking apart a carburetor can lead to nothing but frustration for the uninitiated. Take pictures with your phone to aid in reassembly. Note the positions of any linkages or the settings of any mixture screws, if equipped. If you’re at all reluctant, visit the servicing dealer instead.
Consider replacing the carburetor altogether. It’s a fairly simple process on most smaller mowers and it’s often less expensive than taking it to the dealer.
Direct compressed air from the inside of the air filter out to remove debris that may be reducing airflow and preventing the lawnmower from starting.
Clean/Replace the Air Filter
With the air filter removed, now’s the perfect time to clean it.
Tap rigid filters on a workbench or the palm of your hand to dislodge grass clippings, leaves and other debris. Direct compressed air from the inside of the filter out to avoid lodging debris deeper into the media.
Use soap and water to wash foam filters. If it’s been a few years, simply replace the filter; they’re inexpensive and mark the only line of defense against wear-causing debris entering your engine and wearing the cylinder and piston rings.
An incorrectly gapped spark plug can prevent the engine from starting. Set the gap to the specification given in the owner’s manual.
Check the Spark Plug
A dirty or bad spark plug may also be to blame. Remove the plug and inspect condition. A spark plug in a properly running four-stroke engine should last for years and never appear oily or burned. If so, replace it.
Use a spark-plug tester to check for spark. If you don’t have one, clip the spark-plug boot onto the plug, hold the plug against the metal cylinder head and slowly pull the starter cord. You should see a strong, blue spark. It helps to test the plug in a darkened garage. Replace the plug if you don’t see a spark or it appears weak.
While you’re at it, check the spark-plug gap and set it to the factory specifications noted in the lawnmower owner’s manual.
If you know the plug is good, but you still don’t have spark, the coil likely has failed and requires replacement.
Did You Hit a Rock or Other Obstacle?
We’ve all killed a lawnmower engine after hitting a rock or big tree root.
If your lawnmower won’t start in this scenario, you probably sheared the flywheel key. It’s a tiny piece of metal that aligns the flywheel correctly to set the proper engine timing. Hitting an immovable obstacle can immediately stop the mower blade (and crankshaft) while the flywheel keeps spinning, shearing the key.
In this case, the engine timing is off and the mower won’t start until you pull the flywheel and replace the key. It’s an easy enough job IF you have a set of gear pullers lying around the garage. If not, rent a set from a parts store (or buy one…there’s never a bad reason to buy a new tool) or visit the dealer.
My Lawnmower Starts But Runs Poorly
If you finally get the lawnmower started, but it runs like a three-legged dog, try cleaning the carburetor with AMSOIL Power Foam. It’s a potent cleaning agent designed to remove performance-robbing carbon, varnish and other gunk from carburetors and engines.
Add Gasoline Stabilizer to Avoid Most of These Problems
Which sounds better? Completing all these steps each year when your lawnmower won’t start? Or pouring a little gasoline stabilizer into your fuel tank?
Simply using a good gasoline stabilizer can help avoid most of the problems with a lawnmower that won’t start.
AMSOIL Gasoline Stabilizer, for example, keeps fuel fresh up to 12 months. It helps prevent the lighter hydrocarbons from evaporating to reduce gum and varnish and keep the fuel flowing. It also contains corrosion inhibitors for additional protection.
I have a five-gallon gas can in my garage from which I fuel two lawnmowers, two chainsaws, two snowblowers, a string trimmer, an ATV and the occasional brush fire. I treat the fuel with Gasoline Stabilizer every time I fill it so I never have to worry about the gas going bad and causing problems.
You can also use AMSOIL Quickshot. It’s designed primarily to clean carburetors and combustion chambers while addressing problems with ethanol. But it also provides short-term gasoline stabilization of up to six months.
Use a Good Motor Oil for Your Lawnmower
Although motor oil has no bearing on whether your lawnmower starts or not (unless you don’t use oil at all and seize the engine), it pays to use a high-quality motor oil in your lawnmower.
This is especially true for professionals or homeowners running expensive zero-turn or riding mowers.
Lawnmower engines are tougher on oil than most people realize. They’re usually air-cooled, which means they run hotter than liquid-cooled automotive engines.
They often run for hours in hot, dirty, wet conditions. Many don’t have an oil filter, further stressing the oil.
In these conditions, motor oils formulated for standard service can break down, leading to harmful deposits and reduced wear protection.
For maximum performance and life, use a motor oil in your lawnmower designed to deliver commercial-grade protection, like AMSOIL Synthetic Small-Engine Oil.
Its long-life formulation has repeatedly demonstrated its ability to safely exceed original equipment manufacturer (OEM) drain intervals in the toughest conditions. It provides an extra measure of protection when equipment goes longer between oil changes than is recommended by the OEM.
My Lawn Mower Starts Then Dies: What’s Wrong?
Ahhh…the smell of fresh-cut grass. There’s really nothing like it. However, it’s pretty frustrating to be all ready to tackle those tall green blades only to have your mower fire up and then sputter out. If your lawn mower starts then dies, you want a quick answer about what’s to blame, and what to do to fix it. I’ll share the 4 most common causes to this mower problem and what you need to do to address each.
How to diagnose and fix a Honda Lawnmower, wont start, no fuel, no-spark
When your mower starts then dies it can feel like you’re alone, but this problem is more common than you might think, and the fix can be an easy one.
Let’s take a look at the four most common reasons behind that false start and how to fix them.
Causes for Lawn Mower Starting then Dying
If your lawn mower starts, runs briefly, then dies these are the four most common reasons that’s happening:
- Dirty carburetor / clogged carburetor bowl
- Old gasoline that has gone bad
- Dirty or defective spark plugs
- Too much oil in your resevoir
Below I’ll get into each potential problem, why it can result in a mower that starts then dies, and what you should do to fix it.
Dirty Carburetor or Clogged Carburetor Bowl
When your lawn mower starts then dies, your carburetor is most likely involved somehow.
Think about it. If you live in a northern region, your mower sits all winter … waiting months without any action.
And, if you live in a more temperate zone, your mower works hard year-around.
In both cases, your carburetor is going to need a little TLC.
What’s so important about the carburetor?
Your engine needs a steady flow of gasoline to run correctly. The carburetor is responsible for mixing gas with just the right amount of oxygen to create combustion.
This combustion supplies a continuous rotation of the crankshaft that is necessary to run the mower’s engine.
If your carburetor is dirty or the carburetor bowl is clogged, the process above is compromised, and your engine may start up, but it will not run properly and may die shortly after you pull the cord.
How do I fix it?
Your dirty carburetor needs a good blowout with an aerosol can of carburetor cleaner. This will cost you less than 10 and will last for a season or two. I use the WD-40 Specialist Fast Acting Carb/Throttle Body Parts Cleaner (Amazon link). This cleaner uses a solvent formula to breakdown carbon contaminants, leaving your carburetor clean and gum-free. I give my mower a shot of that every time a mow, right before pulling the cord, and recommend that you do the same.
The only drawback to this particular cleaner is it does not have a straw for targeted spraying. If you need a more precise application, Gumout makes a cleaner (Amazon link) that will do the trick with its jet spray applicator.
You can purchase either product locally, or online.
Unscrew the carburetor bowl and give it a once over with the cleaner. Be sure to clean the screw and hole with the carburetor cleaner as well. This is where the directional spraying straw is particularly handy. When reattaching the bowl, don’t over-tighten the screw. This could strip the threads enough to distort the seal.
What I Do
For carb maintenance, give a light spray near the air intake hole for your mower’s engine just before you start it up. This is typically just behind the air filter. Remove the filter, give the hole a spray, then replace the filter.
When you start the mower, it’ll be pulled into the engine and clean deposits in your carb.
Old Gasoline in Your Mower
You know your mower can’t run without gasoline, but the quality of the gas is equally important.
If the gas in your mower has been sitting inactive for a while, evaporation has most likely created a damaging residue.
This residue leaves particles that clog your mower’s internal parts.
The end result is restricted gas flow, which means your mower can start and die shortly thereafter. Sometimes, your mower won’t start at all.
How do I fix it?
If your mower tank is less than half full of old gas, you might try adding new gas to dilute the impurities. If the old gas is more than half of a tank, it would be best to siphon it out and fill the tank with fresh gasoline.
In both cases, adding a stabilizer such as Sta-bil Fuel System Stabilizer (Amazon link) is a Smart idea. Stabilizers prevent the clogging residue for up to two years, and at around 10 a bottle, they are an inexpensive additive that can keep your mower running like a champ.
Always read the directions to know the proper fuel to stabilizer ratio for your mower.
What I Do
I used to mix Sta-bil into my fuel, but now I just pay a little extra for 4-cycle TruFuel – an ethanol free gas product that can sit for years without going bad.
It’s more expensive than regular gas mixed with Sta-bil, but a couple of larger cans will get my Honda self-propelled mower (this one from Home Depot if you’re curious) through the mowing season up here in New England, and I like the peace of mind that comes with knowing my mower and snow blower always start on the first pull, and I don’t have to worry about bad gas giving me problems when I’m ready to mow or need to clear the driveway.
You can buy it online, or locally at Home Depot or some local hardware stores.
Dirty or Defective Spark Plugs
Spark plugs supply the “spark” that ignites the air/fuel mixture in your engine.
This small explosion makes your engine produce power.
The spark plugs are an essential component of your mower’s ignition system. If they are dirty or faulty, they will not spark, and your mower will not start, or may start and then quickly die.
How do I fix it?
Your mower’s spark plug(s) are easy to find. In most walk-behind mowers they’re covered with a black cable and right in the front of your mower.
You’ll need a socket wrench of the right size to remove your plug (check your manual to find the correct size for your mower/spark plug).
If your spark plugs are not too heavily coated with build-up, you can try cleaning them. You should never clean a spark plug with a shot-blasting cleaner. A wire brush and appropriate cleaner will do the trick if the plug is just dirty.
However, if your mower’s spark plug looks filthy or appears to have a dark carbon residue, you might be better off replacing.
This is an easy job and it’s inexpensive – a new spark plug with be 8-9 and your size is probably available locally.
What I Do
Spark plugs should be replaced every year or two for problem-free mowing, and I do mine annually as part of my spring mower maintenance.
I get a new air filter and change the oil in my mower at the same time. This runs me about 20 total, takes me about 15 minutes, and keeps my mower in perfect working condition.
Replacing Your Spark Plug
Removing your spark plug is an easy job anyone can do. Simply unhook the spark plug wire and remove the old plug with a spark plug socket.
Replacing a spark plug can be a bit more challenging for a first-timer, but I still consider it an easy job.
Use a spark plug gauge to measure the gap between the two electrodes at the tip of your spark plug. Check for the specifications for your model to know the recommended size of the gap.
If necessary, use a spark plug gauge to adjust the gap by gently bending the curved electrode. When the gap is correct, the gauge will drag a bit as you pull it through the gap.
Now you can install the new plug and attach the spark plug lead. Be careful not to over-tighten on installation.
If you have never done this before, there are several videos online that can be of great assistance, but my advice is that as soon as it starts to feel snug, give it no more than another quarter turn to prevent damage.
Too Much Oil in the Mower’s Reservoir
If your carburetor is clean and the spark plugs are firing, the problem might be too much oil.
I believe it’s human nature to want to over-fill a lawn mower’s oil reservoir, especially if you’re not particularly handy. You feel so accomplished that we’re doing the job yourself that you go overboard and over-fill the tank.
It happens, and it’s not the end of the world (or your mower).
White smoke coming out of the engine is a tell-tale sign that excessive oil is the culprit.
If a lot of smoke is coming out, your mower might be running, but not for long. In this case, the excess oil will eventually drown out the engine and cause it to die.
How do I fix it?
This is actually an easy fix. If you have too much oil, you just need to drain some. You can use a siphon, or (if you have a walk-behind mower) you can tip your mower and drain the oil from the hole where you add it.
What I Do
I’m guilty of overfilling the oil tank sometimes too, so I’ve learned to go slow when I add oil. I check, and check again with the dipstick and gradually bring the level up to the proper place.
If you have overfilled your oil tank, I advise that you use a dipstick to measure the amount of oil in the reservoir before removing it, and then again after to make sure you get the right level.
Not enough oil is another (and more serious) problem, and you would not want to inadvertently trade one issue for another.
After draining some oil and checking to see if you have an adequate amount, start the mower again.
If the mower fires and stays running without the billowing puffs of white smoke, you have corrected your problem.
Lawn Mower Starts Then Dies: When it’s Time to Call a Professional
If you have tested all of the methods I’ve shared for fixing your lawn mower that starts and then dies, hopefully your problem is solved.
But if not, it might be time to throw in the shop towel and call a professional.
The following are other issues that could be keeping your mower from running properly.
Serious Reasons Your Lawn Mower Starts Then Dies
- Worn out carburetor: If your carburetor is more than dirty, it might be time to replace it.
- Faulty choke: Unless you are extremely handy, identifying this problem and restoring the delicate balance necessary to get your engine purring like a kitten is another issue for the experts.
- Gas tank or gas line blockage: Anytime your gasoline is not getting to the engine, your mower will not run properly. A blockage of any kind that prevents the constant flow of gas is a problem that might take a trained eye to identify and fix.
The average weekend warrior with limited knowledge on the matter will probably feel more comfortable hiring someone with the experience and the tools to get the job done right.
I recommend that you start by checking your mower’s warranty. If it’s covered, a repair may not cost you anything. Some companies will send someone right to your home, or come to pick up your mower to save you time.
If your mower isn’t covered by warranty, find a local small-engine repair shop that has good reviews. These guys can fix almost anything, and their are typically lower than you’d expect.
Preventing Mower Problems
The best way to ensure your mower will fire up and run like a champ is to put preventative measures in place.
I have tips for winterizing your mower, and a spring maintenance checklist that you can check out if you’d like to learn more.
To summarize those here, however:
- Clean your air filter regularly (replace it annually).
- Change your spark plugs every 1-2 years.
- Keep stored oil and gasoline clean. Use a stabilizer in your gas to keep it fresh for up to two years, or pay extra for 4-cycle TruFuel.
- Keep your engine clean with an engine degreaser.
- Use the dipstick and don’t overfill your oil reservoir.
- Keep your carburetor clean with a carburetor cleaner spray.
Performing regular maintenance on your mower is the best way to keep it running smoothly, and investing a few bucks per year in this is worth it.
You’ll avoid headaches, repair costs, and your mower will last a long time, starting right up when you need it.
If you do encounter a problem with your lawn mower, decide if you are comfortable with trying to fix it yourself.
If the issue seems to be something beyond the basics, don’t hesitate to call a professional. There’s no shame in this, and sometimes do-it-yourself repairs are just not worth the time, energy, or frustration.
But if you are up for the challenge of fixing the problem yourself, the above guidelines provide a good starting place, and online videos may also be useful. I think YouTube is a great resource.
The main thing is that you get your mower fixed so you can get out there and make your lawn the envy of the neighborhood.