When my lawnmower won’t start, the first things I check are for faulty spark plugs, as these components are responsible for igniting the fuel-and-air mixture inside the cylinder of the mower engine.
Quick Answer
If your lawn mower isn’t getting the gas to the spark plug, the first and perhaps the easiest fix is to remove and clean the spark plugs of your lawnmower. Other reasons include:
- Dirty air filter
- Manual Choke left on
- Clogged filters in the fuel pump
- Stuck open valves
Read on for more details and how to fix each issue.
What causes my lawn mower not to pump gas to spark plugs?
Gas-powered lawnmowers 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, the spark plug will fail the ignite, therefore your lawn mower won’t start.
The 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
More 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 mowers.
If the filters are clogged, your lawn mower won’t start because gas will not reach the spark plug.
Stuck open valves
When 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
Several issues 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 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 on top of 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 the air supply into the tank.
- You should- therefore check your gas tank cap’s air hole to see whether it’s been plugged.
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 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 start.
Here are simple DIY fixes you can use to correct the problem and start the lawn mower again.
1. 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. Your lawnmower will still run on old fuel but not very well. 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.
2. 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 too long.
The best fix is to drain off the old fuel from the gas tank and replace the filter. Here’s how to change a fuel filter in small engines.
3. 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:
4. Avoid using high-ethanol gas
If you own a Honda mower, you might want to stick to a gasoline brand with less than 10% ethanol. Higher ethanol levels often cause these lawnmowers to fail to start.
Anything above 10% ethanol and your carburetor will collect up all the atmospheric moisture absorbed by the high-alcohol fuel.
During winter, the vapor turns to water which leaves some type of residue on the carburetor parts. This debris will cause blockage over time and thus interrupt fuel flow. You’ll then end up with a Honda mower that can’t start.
5. Clean the spark plug
A lawn mower not starting doesn’t necessarily mean the fuel is not reaching the engine or spark plug. The problem could be that the spark plug is loose, dirty, or faulty in some way.
To fix this problem and make the mower start, remove the spark plug, clean off any debris, and return it. Make sure it is well-fitted to prevent any electric faults and cut-offs.
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Hi, Alex Kuritz here. Growing up I remember that my family had one of the best lawns in the neighborhood. Richly green and lush. I did a lot as I grew up in terms of caring and tending for not only my family’s lawn but also my neighbors. I can say I have years of experience, and I am here to share it with you.
Push mower started as usual, then sputtered as if out of gas. I stopped and checked gas -almost empty. Filled with new gas and it won’t start at all. I have been mowing about every 5 – 7 days this summer, mower is less than 2 years old and always starts quickly. Gas is not old. I assume a blockage somewhere in the fuel system. Just wondering if there is anything I can do before taking it to a shop. It is a very self contained system, auto choke, etc. Will fuel treatment or any additive help me? I have given it 2 days, shaken the mower…
Another reason for gas not to be getting to the engine is the wrong type of fuel filter. I hire a guy to come to my house once a year to perform maintenance on my Murray riding mower. He replaced the fuel filter with the wrong type. Engines without a fuel pump should use the small red disc fuel pump. These have a high flow rate of 150 microns. I bought one and replaced it myself.
My carb on my riding mower is getting gas but the spark plug is not ? Cleaned the carb installed a new spark plug