It’s the start of spring and the first heavy rain just came to wash away the last of the winter snow. And then you see those sprouts of green start to shoot up faster than you’d like. So, you grab your lawnmower to keep it nice and short.
You’ve checked it has gas and oil already and pumped the primer – and then you give it a pull and it starts. Great! But what if it dies out after a few seconds. If you keep trying this multiple times and it keeps dying you might have a few different issues happening that you can try to tackle fixing.
Lawnmowers are fairly simple small engines and don’t require a lot of knowledge about their inner workings in order to troubleshoot/maintain them. If you start your mower and it dies after a few seconds, try out the following tricks.
Check the Fuel Line
The fuel line typically should be clean from any debris or dirt as the only thing traveling through it should be the transfer of gasoline from the pump to the mower. But when you open the gas tank often small particles can fly in and even the gasoline itself may have some particles in it which may end up getting into the fuel line.
Some lawn mowers may have a fuel filter in the fuel line between the gas tank and the carburetor. If yours does, you can easily replace this if it seems to be clogged with dirt and other junk. This will cause the gasoline not to be able to easily flow to the engine which will cause it to stop after a few seconds.
While typically gasoline doesn’t get old and stale easily unless open to the elements, it can “varnish” which is a term that means the gas has produced a type of solid substance on the walls of the gasoline tank or the internal parts. This typically happens when the lawn mower sits between mowing seasons (in those pesky winter months).
You might be able to notice this if you smell the gasoline and find that it has a sour smell (don’t smell the fumes very long as this can be quite dangerous to your health). To fix this you’ll need to drain your lawn mower gas tang of its entire contents.
Place a large plastic/metal pan next to the lawn mower and open the fuel tank to drain the contents of the gas tank out, clean the fuel lines and then add fresh fuel back into the tank.
Dirty Gas Tank
Just as the gasoline may often become dirty/stale and needs to be replaced and the fuel line needed to be cleaned, the gas tank itself may also need cleaning. All aspects of the gasoline storage, intake, flow and the liquid itself can all become old and dirty which means a good cleaning is in order to get it working properly.
Cleaning the gas tank is a bit more difficult as you’ll need to drain it and then either flush it with fluids or remove it in order to clean it.
Additionally, one key part of the gas tank that can become dirty is the cap on the gas tank. You may not know it, but there is a pinhole in the top of the cap that allows air to flow through into the tank. If this hole is clogged then no air can get back into the tank as the fuel is used up and it ends up killing the motor as the gas can’t enter the motor as well at that point.
Clean off the cap and flush water through the pinprick if possible, to clean it out. Place it back on and start it up again to see if that fixes the issue.
Here’s the video that also might help:
While this isn’t a specific fix to the lawn-mower starting and then dying, it will prevent most of the similar issues with your lawn mower automatically as it will keep everything flowing through it cleanly and maintained. It is suggested to have your mower serviced at least once per year typically in the spring (if you’re in a colder climate).
For this, you’ll need 3 basic supplies including:
- Engine Oil (appropriate for your lawn mower)
- New Air Filter
- New Spark Plug
Typically to make it easy when purchasing these, take out the air filter/spark plug from your lawn mower and take them with you to the store when you purchase the new ones. This way you’ll be able to easily know which one you need to purchase.
The air filter should be replaced once a year along with the spark plugs so that you know the juices flowing in and out are kept in tip-top shape. Start by removing the spark plug from your mower and then drain the oil from the mower by removing the cap and tipping it on its side. Make sure you don’t let the oil just go into the ground as it is very destructive/toxic.
Next, remove the blade from the bottom and give its edges a little sharpen so it doesn’t have to work overtime to keep the grass cut. You can use a file to do this. Ensure to clean under the mower deck so all of the build-ups from last season is removed. Put the blade back on and install the new spark plug on your mower. Lastly, fill up the lawn mower with oil again and you’re good to go!
The most common issue when a lawn mower starts up and then stops a few seconds after is a carburetor issue. Typically, if this is the case, you’re best to let a professional take a look and clean it out as this can get a bit more complicated.
If you do feel comfortable enough to work with them this would be the last step in the troubleshooting process for why the motor won’t keep running. When dirt and varnish from the fuel end up going through the lawn mower it can cause things to get sticky, orifices to get clogged, jets to get clogged, or gum to end up inside it which makes the engine sputter out while it’s running.
By doing an in-depth cleaning of the carburetor including all of its internal components will normally fix this up easily as long as you haven’t let it go too long and it ends up needing replacement. Most times cleaning will get the job done.
If you do plan to clean it there are different ways of doing it depending on the cleaner you get. Some simply require you to remove all of the connectors and spray all of the connectors/openings. After letting it sit for a while you then wipe it down and re-connect everything.
Another way is by taking apart the carburetor (make sure to take photographs of how all of the pieces went together first as this be helpful when reassembling it). Once all of the pieces are separated then place them in a container filled with carburetor cleaner. You can then let them soak for about an hour or however long the instructions on the cleaner state. Once completed, rinse the parts with water and let them dry completely. You can use an air compressor to speed up this process if needed. You will need to ensure that all of the water has dried completely as water should not be present here as it will cause issues with starting the lawn mower.
Once all of the parts are cleaned and dried you can then reassemble the carburetor and re-mount it on the mower again connecting all of the pieces and parts. Because this can be a bit of a complicated process you only want to do it if you have some experience/confidence with this type of task. If you are unsure, find a local handyman who has experience with it and asks them to teach you so you can self-sufficiently do this in the future.
If in doubt, it’s best to contact a professional for the carburetor cleaning.
Lawn mowers can be pesky to keep maintained but if you follow many of these simple steps to make sure everything is cleaned it will often fix all of the issues you may encounter. As a last tip, although you won’t be in contact with many dangerous chemicals, oil and gas are still not good to come into contact with your skin.
Ensure you use gloves whenever cleaning the parts of the lawn mower. Additionally, do not ever spray any liquids onto the electrical connectors including the spark plugs and if they do get wet ensure they are dried off completely prior to starting up the lawn mower again to avoid any permanent damage to the motor components.
Hopefully, after following these steps your lawn mower will be running in perfect condition all season!