Your Lawn Mower Starts Then Dies: Try Our Tips
Wow, it’s the weekend! And such a beautiful day the sun’s out and your lawn needs a mow. If you’re anything like me the sooner you get your mowing chores done the more time you have for weekend fun stuff. But wait! Your lawn mower starts fine then dies? What happened? What’s wrong? Well, if this crazy scenario just trashed your weekend and your motivation just went out the window because of a malfunctioning mowing machine, you’re not alone my friend. Just like us, there are days when something goes wrong and we can’t seem to do anything right.
Yet, lawn mowers are basic machines that you can easily fix if you read our troubleshooting guides. In no time, your weekend can get back on track and you’ll be whistling away while mowing your grass and turning your lawn into a bowling green again.
There are a number of possible causes why a lawn mower starts then dies. It could be a failure with the spark plug, lack of gas flow to the engine, a clogged air filter and the most common is a dirty carburetor. Actually, most of the problems that stall the engine while it is just starting come from the carburetor. But what is a carburetor and what is its function? Its a most important part of an engine and yet can be the main cause of lawnmower problems?
All small gas-powered engines are equipped with carburetors, particularly the 2- and the 4-stroke lawnmower engines. Its main function is to mix gas and air to convert it into a more combustible form of gas for the engine to use.
The carb, as we call the carburetor, is designed to allow air and gas and do the proper mixing. So whenever you start your lawnmower’s engine, fuel will flow from the tank and pass through a hose, and goes inside the chambers of the carburetor. In the case of a 4-stroke engine, it has its bowl that holds the gasoline, and inside it is a floater that controls the inflow and outflow of fuel much like what you have in your bathroom’s toilet float system.
What Happens When the Engine Starts?
When the engine starts, air will be sucked through the air cleaner and this will be pressurized inside the carburetor. The carburetor will then atomize the fuel and mix it with the pressurized air to turn it into a fine mist.
This atomized gas will then be sprayed onto the spark plug inside the combustion chamber. Because the spark plug is charged with electricity, the air-gas mixture which we call air-fuel ratio (AFR) will generate a spark and that begins the internal combustion in the cylinder.
So as long as there is a continuous supply of gas and oxygen from the carburetor, the combustion process will go on and the rotation of the crankshaft will also continue. Unfortunately, if your lawnmower starts then stops then 1 or several of these steps are not working correctly.
Lawn Mower Starts Then Stops - Problems in Carburetor
Now we will talk about the usual problems why your mower starts then stops due to carburetor issues. The carburetor is the main mechanical system that’s a separate part of the engine that mixes air and fuel so if there is a problem with it, your lawn mower will surely experience some issues particularly with stalling. Below are a number of the common carburetor problems and easy fix solutions.
Carburetors have lots of screws so each of these should be tightened because the chambers inside are where the air and gas mixes and passes through. If there’s a leak due to a loose carburetor, there will be an insufficient flow of fuel and the atomization of gas will be affected. With an unstable air-gas mixture, the mower starts then stops occasionally.
Make it a habit to check your carburetor always to see if everything is secured and firmly fixed. Wiggle the carburetor a bit and test the tightness of the screws using a screwdriver.
Sediment or residue clogging the carburetor
One of the reasons why a lawn mower starts then dies is because of blockage of the internal parts of the carburetor. This could be due to the gunk that has formed from old stale gasoline in the carburetor bowl.
Drain out the old gas. Unscrew the bowl which you can find underneath the carb and check for trapped dirt. If there’s gunk inside, scrape it out. Spray the inside of the carb also with the carburetor cleaner and reattach the bowl. Start the engine and observe. Put in fresh fuel and add a fuel stabilizer. This can improve the quality of the fuel and can prevent gasoline residue formation for up to 2 years with stabilizer.
Clogged screw pin in the carburetor
You will find in many carburetors the fuel bowl located underneath the carb body. This bowl is where the fuel is stored before it enters the carb for fuel to be atomized.. At the bottom of this bowl is a screw pin that has a hole and a seal in it and its function is to regulate the downward movement of gas. If the hole in this screw gets clogged up due to gasoline sediments or dirt, the downward movement of gasoline from the inlet would be cut off and that could be a reason your lawnmower starts then stops.
Carefully remove the screw. Clean out the bowl and check the hole in the centre of the screw. If you see it clogged or even if it’s not, use a thin wire to clear out the hole with possible debris lodged inside. Spray the inside of the carburetor with a carb cleaner to ensure that the remaining sediments will be dissolved. Reattach the bowl but do not tighten the screw too much to avoid damaging the seal.
Defective or dirty spark plug
One of the most common reasons that a lawnmower starts then stops is a problem with the spark plug. Because the spark plug produces the spark to complete the air-mixture combustion, once there is a carbon build up between the side electrode and the center electrode which is the part of the spark plug that generates an electrical spark, there is no possibility of a spark as these two parts need to have a clear gap for the electricity to jump from one electrode to the other.
Carbon deposits can be caused by an overly rich gas-air mixture or it could be due to a clogged air filter. Another cause of spark plug failure is due to oil deposits that can be caused by the breakage of the spark plug tube seal. This seal or gasket prevents oil contamination when there is a spilling of oil during oil replenishment or oil over spilling. Dirt can also get into the seat of the spark plug and contaminate the electrode.
The best thing to do with carbon deposits is cleaning it by first disconnecting the spark plug from the wire cap. You can just pull it off with your hands. Then using a plug socket unscrew the spark plug be sure not to damage the porcelain neck. Clean the plug seat to ensure no soot or carbon deposits remain. Use a wire brush when cleaning the gap between the side and the center electrodes and spray this with a plug cleaner or a carb cleaner. If you don’t have a wire brush you could use sandpaper or a small nail to clean out the gap.
With oil deposits due to breakage of the seal, best to replace the spark plug with a new one but clean the plug seat first. If oil continues to seep into the spark plug chamber, this could mean the problem comes from inside the cylinder like a failing gasket or the rings of the piston have worn out. In this case, better bring your machine to a shop for repairs.
Blocked fuel cap
Did you know that even the cap of your lawn mower’s fuel tank can be a cause why your lawn mower starts and dies? In most lawn mowers, their gasoline caps have holes to stabilize the pressure inside the gas tank. Once this hole is clogged by dirt, the pressure will develop a vacuum that can disrupt the flow of gasoline to the carburetor. Fine dirt can easily penetrate this hole so for every filling of gas, you should check this hole thoroughly.
The hole can be easily cleaned out with a thin wire. But if the cap has already seen better days, better to buy a new cap from your lawn mower’s manufacturer.
Pouring too much oil in the oil reservoir
Another common reason why a lawnmower starts then stops is by putting too much oil in the crankcase. So if you have cleaned out the carburetor including making sure all the holes are free from dirt and sludge. Then you start your mower and there’s white smoke coming from the engine, this is also a possible cause of a stalling lawn mower. If the oil has been overfilled . This means that some of the engine parts are being drowned by too much oil and the excess will be burning which produces the white smoke.
To know if too much oil in the crankcase is causing the lawn mower to start then die, tilt the machine up and secure its handle with a heavy object to hold it. This will allow the oil to circulate into different parts of the engine that are hard to reach by oil. Let your mower stay in this position for an hour then run its engine for a few minutes and observe if it’s stalling and the white smoke disappears. If the engine keeps dying and white smoke still appears, do the next solution.
How to Change Oil in Craftsman Lawn Mower Click Here
The next thing you can do if you suspect that too much oil is the culprit is drain about 1/4 of the content oil of the machine then use the dipstick to measure the oil level. Be aware of the level at the end of the dipstick and the oil level must not be over the upper line. Drain excess as necessary. To drain oil, locate the drain plug which is usually underneath the mowing deck. If there’s no drain plug, open the oil cap and tilt the machine towards the direction of the oil filler cap and catch the oil with an oil pan. Learn more about
How Much Oil To Put In Lawn Mower Click Here
Old, malfunctioning carburetor
An old worn carburetor could also make your mower start then stop. And should be replaced immediately. Especially if your lawn mower has been cutting your lawn for a lot of years and has not undergone any major repairs or an overhaul. The carburetor has a lot of moving parts and it doesn’t take much for it to malfunction.
Needless to say that if you have to replace your carburetor, you must be comfortable with dismantling and replacing it .Some of the things you need are carburetor cleaner or oil degreaser, fresh oil and fresh gasoline. We won’t recommend you buy a carburetor especially if you have an old mower (10 years or older) Because what we have found is that by the time you buy a new carb, spend half a day fitting it to your old mower. Then hope like hell it actually fixes the problem. You may as well just buy a new mower with a warranty. They can cost as little as $200. Here are my 3 best choices.
Clogged air filter
A lawn mower always needs air to maintain its combustion for the air-fuel mixture and it needs clean air to do this. If there is insufficient air coming to the engine because of a dirty air filter, this can cause the air-to-fuel ratio to be overly rich thus can cause sputters or stalling of the machine. So most likely when the mower starts then stops while the carburetor is still in good condition, the problem could come from a clogged air filter.
So before you start the engine, don’t forget to check the air filter which is very easy to remove and clean. There are 3 types of air filters for lawn mowers and each type requires a specific cleaning method. These are the foam, paper, and dual-elements.
A dirty foam air filter only needs washing with soap detergent and water and squeezing until all the dirt and oil residue is gone. Then dry it by squeezing it again while wrapped in a clean cloth. You can put 2 or 3 drops of engine oil on the sponge and squeeze it again to spread it. This is to make the sponge more effective in filtering out dust and dirt coming from the air and soil.
The paper type filter can be cleaned using compressed air but if it is worn out, replace it with a new one. These types are disposable. The dual-elements have sponge and paper cartridges in them. Clean the sponge as described above and use compressed air on the paper filter. This is a very easy fix as air filters are very cheap to replace. Sometimes it’s not worth trying to clean them.
Moisture in the gas tank
Moisture can get into the gas tank in many ways – due to leaks on the tank, crack in the fuel cap, loose fuel cap or gas refilling during rain. Unfortunately, moisture with gas can cause your lawn mower to start then die right away or the engine may be very hard to start then stalls even if you throttle it. The cause of these issues is the disruption of the air-fuel ratio due to moisture that creates an imbalance in the burning of fuel.
Another problem with moisture in the tank, since water is heavier than gasoline and goes to the fuel line, this can freeze up with extreme cold and can ruin the fuel system.
Once you see moisture in the fuel line, the best you can do is drain out the gas fully and put new gas in again. But before you pour in the gas, you have to check how the moisture came about. Check the hose that carries the fuel to the engine if this fits tightly. Replace the hose if it’s worn out or loose. Inspect also the rest of the fuel tank including the cap for cracks.
Remove the cap, hold it above your head Look through it using the brightness of the sun and look under it while bending it a little. If you see some light seeping through, the cap is cracked. Check also its tightness when you refill your tank. A loose or cracked cap should be replaced. More about
Other Reasons Why Your Push Mower Starts Then Dies
If using a carb cleaner doesn’t work and your push mower still starts then dies if you’re running out of ideas and options, why not let an expert check your lawn mower out. So here are the things you should ask your mechanic to check :
As we have mentioned, there are many reasons why a carburetor needs replacement, particularly when it gets old. Lawn mower carburetors can easily get dirty because of the jobs that they do. That’s why they are also vulnerable not only to clogging but also to physical damage particularly with their small internal parts. Think about its floats, needles, shutters, and other small parts. If any of these get damaged or get out of shape due to lack of maintenance or the carburetor itself doesn’t fit anymore to its seat, then better have it checked by an expert and a carburetor replacement may be necessary.
Every 2 or 4-stroke engine has its choke features and its function is to allow you to adjust the intake of fuel into the air-fuel mixture while reducing the intake of air to create a temporary richer mixture. We use the choke usually during the cold weather or when the engine gets cold. But if your lawn mower keeps dying even after you choke the engine, most likely there is a problem with the choke system or with the filter assembly or the throttle linkage.
What Should Be Done:
If you’re not confident in checking the choking system or the linkages and your lawn mower won’t’ stay running, better take your machine to a repair shop. The mechanic will refine the choke or adjust it or may replace parts as necessary.
Blockage in the gas line or gas tank.
This is one of the most common problems why a lawn mower runs for a minute then stops – blockage in the gas line or tank. Some dirt may have accidentally dropped into the tank while you are gas refilling and causes the blockage. Eventually, the blockage will constrict or stop the flow of fuel into the engine making your lawn mower run then stops.
What Should Be Done:
If you discover there is a blockage in the gas tank, you can do a few things to eliminate the sludge or dirt. You can either drain the gas hoping that the blockage will flow out with the gas, or siphon the blockage if it’s too large to pass through the hose but this requires a special technique. You can also drain the fuel and remove the gas tank from the engine and clean it with a cleaning solution. But if you’re not up to these tasks, taking your machine to a repair shop would be much better.
How to Prevent Common Lawn Mower Issues
Now that you know some of the common problems why a lawn mower starts then dies, or maybe you have a flooded lawn mower
you also need to know the best maintenance tips on how to prevent these problems from occurring. These tips will help you prolong the life of your trusty grass-cutting machine and avoid spending too much on repairs or replacement.
Have your air filter cleaned out regularly.
If you’re a beginner with how your lawn mower works, the air filter acts as the primary defense of the engine against dirt and debris. It keeps the dirt from the engine through the carburetor. When the air filter gets clogged up with dirt or cut grass or with its oil, fresh air cannot enter and can choke the engine causing the lawn mower to die after starting.
lawn mower spark plug replacement each year
Not many people know that their spark plug need to be maintained too, especially if the machine is frequently used for an extensive period. The function of the spark plug is to create the spark to burn the fuel inside the combustion chamber. But if it becomes worn out or goes bad, this will not produce an efficient electrical spark and the machine will experience hard starting and will frequently stall.
The common signs that your lawn mower’s spark plug need to be replaced are the following:
The efficiency of the machine has decreased due to the lack of combustion power given by the spark plug.
The mower has difficulty in starting.
The engine runs then stops.
Experts suggest that every mowing season or once a year is the best time for changing the spark plug and with the use of the proper tools, it’s a no-brainer to replace it. But note that you should buy only branded spark plugs.
Use only fresh gasoline and use a stabilizer.
This is self-explanatory but in essence, to avoid moisture in your gas tank and prevent the accumulation of sludge or sediments from old gasoline inside the tank, putting in a stabilizer can retain the freshness of the fuel for months while it can also smooth out the operation of the machine.
Always clean the lawn mower after use.
Cleaning the lawn mower immediately after use can also prolong its life. By eliminating the dirt while it is fresh and not hard to get off, this will enable your engine to breathe and prevent the dirt from going into the engine’s nook and crannies. Include the underside of the lawn mower when cleaning by spraying water with a garden hose and the engine can be cleaned with water mixed with car washing detergent. You can also detach the blade and sharpen them up to be ready for the next mowing season.
Always use a carb cleaner when cleaning the carburetor.
If the lawn mower won’t stay running, cleaning a carburetor can solve the problem and this can be quick and easy with the use of a carb cleaner. These products are specially formulated to dissolve sludge and gunk that have deposited inside the carburetors and to their hoses. If your lawn mower starts then dies quite often, it would be better to have a carb cleaner on hand for a fast fix .
Mower Starts Then Stops - Can Carburetor Cleaners Stop This
If you noticed, we always recommend the use of carburetor cleaner every step of the way in cleaning the carburetor of lawn mowers. But did you know the benefits of using these cleaners? Here are some of the things they can be good for.
It can clean your carburetor inside which helps in the distribution of the right amount of fuel necessary in achieving the exact air-fuel ratio.
It can dissolve stubborn built-up dirt inside and outside the carburetor and there’s no need for scrubbing or even disassembling your carburetor. Just unscrew the carb bowl and do a quick spray inside until you see the dirt dripping out and that’s how easy for this stuff to work.
Not only is it effective in cleaning and degreasing your carburetor and preventing the problem of a mower starting then stopping but it can also be used in cleaning out the inside of your cylinder if you are disassembling it. So carb cleaners are actually all-purpose degreasers and dirt dissolvers.
Always handy in achieving better performance for your lawn mower engine. Since dirt is the usual culprit getting trapped inside the carburetor, the carb cleaners are the only solution to clean this dirt out without detaching the carburetor completely.
Types of Carburetor Cleaners
There are different types of carburetor cleaners and these are the chlorinated,non-chlorinated, aerosol spray, and dipping can. Some of the chlorinated types contain volatile organic compounds which unfortunately are banned in some states. However, these compounds are what make the carb cleaners more effective in clearing out dirt.
The non-chlorinated carb cleaners are less toxic but are more flammable. So being flammable means you don’t use them in a very hot environment but are effective cleaners if used inside the garage. They don’t, however, dry out easily unlike the chlorinated types that dry in seconds but are still safe to use on materials with plastic components.
The aerosol types which are usually in spray cans are the most common and effective in reaching even the inside of your carburetor especially in cleaning up passages, crevices, and holes. The carb cleaner dip can types are best preferred for those who want to soak their engine parts in a pan for overall cleaning.
Now that you have learned a lot about carburetors and how they work including their usual problems if your lawnmower starts then stops, hopefully, you will know what to do once your machine dies on you after a few seconds of starting. And we have also provided you with the best information about how carb cleaners work.
So the next time you mow your lawn and your mower is hard to start then stalling, try these troubleshooting tips. These may save you a lot of money going to the repair shop. A simple fix with a professional mechanic can cost a good amount of money. However, if you have done everything you have learned here and still your lawn mower starts then dies. Look into buying a new machine rather than repair a really old mower because these days you can get a good mower for a great price.