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.
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 Carburetor Maintenance Tips – Step By Step Guide
Today you’re going to learn how to save a lot of money. How? By learning how to perform your own maintenance on the lawn mower carburetor. Cleaning the carb is easy and a less than 1 hour job to save you 100s of dollars a year. First up, you’ll see a quick-guide on how to remove your carburetor for cleaning (and how to clean it). Then we’ll go into more detail about the carb and what it does and why maintaining it is important. Okay, let’s do this.
Carb Maintenance – 10 Quick-Steps
- To start: find and remove carburetor from lawn mower (you may have to remove some parts to get to it – it will usually be behind the air filter). Be sure to clamp off the fuel line before removing.
- With the carb removed pull the gaskets away and look for damage – replace if necessary.
- Initially clean exterior with a spray carb cleaner you can buy from any hardware store.
- Remove the carb bowl – be careful as regular gasoline will still be present. Have a plastic container below.
- With the bowl off you have access and can start to disassemble the flow and metering needle. Now, remove the screw holding the main jet to pull apart. Now remove the emulsion tube in the carb head. And finally remove the round seal gasket from the outside diameter (replace with new gasket).
- Remove the idle screw to get access to the screw covering the pilot kit (see video for visual of which screw is which).
- With everything disassembled you can clean the internals of the carb with the carb cleaner. If you have access to an ultrasonic cleaner use that as well.
- Now go through and clean all the parts you pulled apart from the carburetor.
- Put everything back together. Be sure there is no residue left from the old gaskets – if there is remove with a knife blade.
- Install carb back onto lawn mower and re-install the fuel lines and air filter/cover.
Watch the carb cleaning video for visual directions:
Now let’s look at the lawn mower carburetor in more detail.
How a Lawn Mower Carb Works
They are tasked with mixing fuel and air together before sending it to the engine. Gasoline is flammable, so it needs to be carefully combined with air before it can be used as fuel. The carb has a number of small parts that work together to create the ideal mixture of fuel and air.
The carb bowl holds a small amount of gas, which is then drawn up into the throat by the action of the diaphragm. The diaphragm is connected to the engine’s intake valve, which opens and closes to allow air into the engine. When the diaphragm moves, it also opens a small port that allows gas to flow from the bowl into the throat. As the gas flows through the throat, it mixes with incoming air and is drawn into the engine. Carburetors are fairly simple devices, but they play a vital role in ensuring that lawn mowers run smooth and efficient.
The Importance of Maintenance
Like any machine with moving parts, a lawn mower requires regular maintenance to keep it running smooth. One of the most important parts of a lawn mower is the carburetor. It controls the mixture of air and fuel that is delivered to the engine, and over time, it can become gummed up or out of adjustment. If you notice that your lawn mower is struggling to start or running rough, it may be time to clean or adjust the carb.
Fortunately, this is a relatively simple process.
Check The Air Filter
A dirty air filter can restrict airflow to the carburetor, causing the engine to run lean. Lean engines run hot and can damage other engine components. Check the air filter regularly and clean or replace it as needed.
Clean The Fuel Tank
Over time, the fuel filter can become filled with dirt and debris. This can clog the fuel line and prevent the carburetor from getting the gas it needs to run properly. Drain the tank and clean it out regularly to prevent this problem.
Inspect The Spark Plug
A fouled or damaged spark plug can cause starting and running problems. Inspect the spark plug regularly and replace it as needed.
Check The Carburetor
The carburetor can become gummed up with dirt and debris, causing starting and running problems. Clean the carburetor periodically to keep it in good working condition.
Clean The Lawn Mower Carburetor
Over time, the carburetor can become clogged with dirt and debris, which can prevent the engine from running properly. Therefore, regular cleaning is important. There are several ways to do this, but one of the most effective methods is to use a spray-on cleaner.
- First, remove the air filter cover and spark plug from the engine.
- Next, spray the carburetor cleaner into the carburetor and dirty spark plug. Then allow it to soak for several minutes.
- Finally, use a brush to scrub away any remaining dirt and debris.
By following these steps, you can keep your lawn mower running smoothly for years to come.
Adjusting The Air And Fuel Mixture
The carburetor controls the amount of compressed air and fuel that enters the engine, and the right mixture is essential for optimum performance.
If the mixture is too rich, it will cause the engine to run excessively rich, resulting in reduced power and efficiency. If the mixture is too lean, it can cause pre-ignition, which can damage the engine. The ideal mixture is about 14.7 parts air to 1 part fuel.
To adjust the mixture, you will need to adjust the screws on the side of the carb.
Start by turning both screws counterclockwise by 1/8 turn. If the engine slows down, turn both screws another 1/8 turn. Repeat this process until you reach the desired mixture. With a little practice, you will be able to fine-tune your carburetor and keep your lawn mower running like new.
Store The Lawn Mower Carburator In A Dry Place
To avoid small engine problems, be sure to store your mower in a dry place where the carburetor won’t be exposed to moisture. Also, use a cover to protect from the elements.
By following the above-mentioned tips, you can keep your lawn mower’s carburetor in good working condition and extend the life of your mower. Be sure to clean the carburetor regularly, adjust the air and fuel mixture as needed, and store your mower in a dry place.
About your guide: Jamey Kramar is a certified Lawn Care Manager (NALP) and a Mechanical Engineer by trade. He has been writing about outdoor power equipment for 11 years and has been quoted in NYTimes, Popular Mechanics, HowStuffWorks, iFixit, Realtor.com, and more. He spends his spare time disassembling things and also building an off-grid cabin at his 200-acre property.
Lawn Mower Carburetor Not Getting Gas
I was mowing and it just died. It was like it ran out of gas. I looked and I had a third of a tank. From that point on it would only run if I sprayed gas in the carb. When I do it right it runs at an idle speed only. It is not getting gas to the jets in the throat of the carb.
I replaced the carb with one I know works, but the same thing happens. So far at least 3 experts including Briggs Stratton techs are baffled. It is a YT3000 Sears with a 21 horsepower engine and 46 inch cut. Thanks.
Answers
Check all the fuel lines to the carburetor. If those are good, then check the fuel pump.
All that has been done all my info says ethanol gas causes problems and no fuel is coming out of the jet other then that its all flowing great also even when I spray gas I can’t get past a fast idle.
I would suggest starting off by downloading the YT 3000 operation manual. Here they have a help section and a carburetor design. It seems you are having an issue with the ethanol gas. I would start by taking my carburetor apart and giving it a good cleaning. You could have a stuck valve inside the carburetor that isn’t allowing the gas to flow freely. You might need to replace your fuel jets on the carburetor. Here is the manual you can download online:
Jets are all clear. I have replaced the carberator coil gas and spark plug. It will start and run smooth at idle speed as long as I spray gas in the throat of the carb.
It seems you have tried everything the experts instructed you to do but nothing worked. have you talked with the Sears Service Center about this problem? I know they have always been helpful with my problems and usually have suggestions to try (given over the telephone) but its for sure they should know more about your mower even if others have failed.
Did you also replace the fuel lines and the filter? If not, replace those fiirst before thinking about the fuel pump.
Some gas lines after exposure to ethanol will pinch under even the slightest vacuum. Replace the fuel line.
Check your wires. that plug in to bottom of carb. That allows gas to go in it might need pushed up to plug in properly. Try that and hopefully that fix your problem.
Questions
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Question: Mower Carburetor Not Getting Gas?
I have a Sears 16 HP twin riding mower. When I went to start it the engine didn’t suck gas through the gas line. After cleaning the carburetor the engine sucks gas part way to the carburetor. What do I do? How do I check the fuel pump and where do get a new one?
Answers
Could the fuel line need blowing out? Or do you need a new spark plug?
The fuel pump works off a vaccum so make sure your vaccum hose is good n has no bad places.
I have used my Craftsman 42″ lawn tractor for over 25 years. the vast majority of those years I used regular 89% gas. no problems. I used the same gas in my Honda ATV. but I do not use the ATV often, and it became hard to start. I removed the carburetor, and the metal had turned green. I ordered a new carburetor. installed a new play, and breather, and the problem was solved. I decided it was time for me to switch to no ethanol gasoline. It was only a few weeks before I had a problem with my mower. It cut off during cutting with no warning. I removed the gas reservoir cap, and saw a couple black things floating in the gas. Then I inspected the gas filter, and saw tiny specs of black inside the filter. I pulled the tank off, cleaned it. I also removed the rubber gas lines and found one was eroding at the connection to the gas filter.
The gas lines are only a couple years old, so I assumed that changing from regular gas to high octane gas must have caused the rubber to break down. I cut off the ends on the rubber gas lines, blew out the lines, checked for any obstructions, and reinstalled them onto the filter. I cut grass almost every day when the weather permits. It is my relaxation. I do have a problem that I had once before, and I can’t remember what it was. I can be riding along with no problems and my mower will shut off, with out any sputter. I look at the gas filter and it is empty. I get off. wait a few minutes. the filter is again full, and my mower cranks perfect, and runs for about 30 minutes and the exact thing occurs. Like I stated this happened a long time ago, but I can’t remember what the fix was. please someone remind me.
Archives
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Archive: Mower Carburetor Not Getting Gas
I can’t get my lawnmower started. I have changed the fuel, changed the spark plug, changed the air filter, changed the air filter gasket, and changed the oil. When I dump lots of fuel in the carb it will run for about 2 seconds, then it dies. Any suggestions?
Archive: Mower Carburetor Not Getting Gas
I have a 4 HP Briggs and Stratton push mower (Murry). the carburetor is not getting any gas, even when the tank is full. Do I need to get another or is there some other things I can try first?
Archive: Mower Carburetor Not Getting Gas
I have a Briggs and Stratton engine on my push mower. The primer will not move any gasoline to the carburetor. Once I took the carburetor apart and it worked for a short while.
Lawn Mower: Only Runs With The Choke On
If your lawn mower only runs with the choke on, check the carburetor. Our repair and symptom guide will help you identify the problem and how to fix it. If you need specific repair instructions related to your model, refer to the manual provided by the manufacturer.
If your lawnmower will start and run with the choke on but dies when the choke is turned off, it may have a problem with the carburetor. The carburetor brings air and fuel together and mixes them in the perfect ratio for combustion before they enter the engine. There are several passages in the carburetor that allow fuel to enter the air stream depending how the throttle is set. The idle circuit, for when the throttle is nearly closed and the engine is idling. The transition circuit, for when the throttle is transitioning from idle to full. The main jet is used when the throttle is at full. The choke assists with providing additional fuel when the engine is first started. When closed, the choke plate restricts most of the incoming air from entering the carburetor’s venturi. This creates additional low pressure in the venturi and also forces air to.
If your lawnmower will start and run with the choke on but dies when the choke is turned off, it may have a problem with the carburetor. The carburetor brings air and fuel together and mixes them in the perfect ratio for combustion before they enter the engine. There are several passages in the carburetor that allow fuel to enter the air stream depending how the throttle is set. The idle circuit, for when the throttle is nearly closed and the engine is idling. The transition circuit, for when the throttle is transitioning from idle to full. The main jet is used when the throttle is at full. The choke assists with providing additional fuel when the engine is first started. When closed, the choke plate restricts most of the incoming air from entering the carburetor’s venturi. This creates additional low pressure in the venturi and also forces air to be drawn through a port on the front of the carburetor body. This port leads to the air space at the top of the bowl. This air pressurizes the space above the fuel in the bowl, which forces fuel to flow out the main jet, into the venturi. This rich fuel mixture makes it easier to start the cold engine. Once the engine fires up and runs for few a few seconds, the choke is opened and the other fuel passages in the carburetor do their jobs as normal. An engine that will fire and run with the choke closed but dies when the choke is opened likely has debris at least partially blocking the fuel passages in the carburetor. In this condition the closed choke provides enough extra fuel to enter the engine to overcome the lack of fuel flowing through the other passages. The engine runs until the choke is opened. The fuel supply is then starved by the blocked fuel passages, and the engine dies. You have a couple of choices to solve this problem: clean the carburetor or replace it. Most carburetors can be cleaned and made to run like new again. Cleaning a carburetor isn’t difficult, but it does require the carb to be mostly disassembled. Replacing a carburetor is a fast and easy repair. In some cases, the new carburetor is so inexpensive that it really doesn’t make sense to clean the old one. Usually the cost of a new carburetor versus your amount of repair experience and skill will inform the decision to clean or replace. To begin cleaning your carburetor, remove it from the lawnmower and carefully disassemble its components. Remove the bowl and drain any fuel out of it. Notice that there is a gasket that seals the bowl to the carburetor as well as one to seal the bowl screw. If either gasket is damaged or cracked it should be replaced. Remove the pin that the float pivots on and the metering needle. The metering needle should be inspected for corrosion and wear on the tip of the needle. Dirt or corrosion on the tip or the needle seat will prevent the needle from closing completely. This will cause fuel to continue to flow into the bowl and spill out of the carburetor’s throat. Remove the main jet and the emulsion tube. Dirt or corrosion can clog the tiny opening in the jet or the series of holes cross-drilled in the emulsion tube. These tiny openings can be cleaned with carburetor cleaner and compressed air. trimmer line can be used if needed to help clean debris out of the openings. Never use anything metal when cleaning a carburetor. Metal picks, wires, or other tools can easily alter the size of the openings, changing the amount of fuel that can flow through them. Next is the pilot jet. There will often be a plug or screw on the carburetor’s body that covers the pilot jet. Access the pilot jet and clean it with carb cleaner, compressed air, and trimmer line if needed. Once the carburetor has been stripped down you can clean the carb body and bowl. Use carb cleaner to thoroughly clean each tiny passage in the carburetor. Also clean the bowl, main jet, pilot jet, and emulsion tube with the carb cleaner. Use compressed air to remove any residual carb cleaner from each component. If you have an ultrasonic cleaner in your arsenal of tools it will work great to clean your carburetor. Ultrasonic cleaners do an amazing job of cleaning the tiny openings and passages in a carburetor. Often times an ultrasonic is the only way to save a badly plugged carburetor. Replace any part in the carburetor that was too dirty to clean or that was damaged by corrosion. Carefully reassemble the carburetor after cleaning and reinstall it onto the mower.
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How To Stop Your Lawnmower Carburetor From Clogging
The best way to prevent a clogged carburetor is to take it off and clean it relatively frequently. Try to clean your carb once after every couple of uses or after you have left your mower in storage for a while.
You can also prevent clogging by buying a high-quality mower. Briggs and Straton is a well-known brand whose lawnmowers are made of quality components that are resistant to rusting and gumming out from dried-up gasoline.
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.