We’ve all been there, you are ready to start the mower for the first time in the season, and it just won’t start. Don’t despair, there are a few common and easily reparable reasons why a lawnmower won’t start. Common reasons include bad gas, spark plugs, and carburetor issues.
There are a few things to keep in mind when trying to start a lawnmower that’s not starting:
- They’re Carbureted– Well, most of them are. Carburetors area technology that hasn’t been seen in cars and trucks regularly since the 1980’s. This means that there is a generation of people coming up that have no idea how to deal with a carb (which can be tricky).
- Air/Fuel/Spark– Assuming that your engine isn’t seized or locked up, these three ingredients in the proper combination will have your lawnmower starting every time.
- Safety Mechanisms– Mowers have mechanisms that keep the mower from hurting you. When they fail, the mower won’t start.
This guide is written for riding lawn mowers or push mowers. They function relatively the same way.
Fuel System Issues
Fuel issues are the most common reason that a lawnmower won’t start. It’s smart to start there. Every season, you should inspect the fuel lines and make sure that they are free of cracks. Replacing the fuel filter every few years is a great idea in general.
Outdoor power equipment needs to be choked when it starts. Sometimes it’ll only run for a second or two before it needs to have the choke backed down a bit. This can be tricky on some models and in some weather. Keep at it.
A carbureted engine can flood. Flooding occurs when raw fuel spills over the bowls and dumps straight into the combustion chamber. When this occurs the spark plug gets wet with fuel and can’t spark. The best way to start a flooded engine is to floor (or in this case find the bunny) the accelerator and clear the fuel out of the bowls. It seems counter intuitive, but anyone who’s driven a carbureted vehicle will tell you that is exactly what needs to be done when it floods.
You can always grab a Pepsi and let the plug dry for a few minutes and try again.
If your mower won’t start, the first thing that you should look at is fuel. How old is the fuel? Has it been sitting in the lawnmower or a gas can for a long time? Gas does go bad. It really shouldn’t be stored for over six months without some sort of fuel stabilizer in it. Then it’s ok for a longer period of time.
If this is your first time starting the mower for the year, this is a very common issue. If it was just running last week with the same fuel, obviously not.
Clogged Fuel Filter
Just like any vehicle, the fuel filter on a lawn mower can go bad. Lawn mowers are gravity fed fuel, which is why they have a primer bulb and means that they are going to be more likely to stop running if the fuel filter is clogged. There’s nothing pulling the gas through.
If you suspect a clogged fuel filter, it’s easy to tell if they are. Most of them are clear. Take a look. If you don’t see any gas passing through it, you know that it’s bad. Also, if you crank the engine for a few minutes, and don’t smell any gas, that’s a clear indication of a fuel issue.
Stuck Needle (Bad Carb)
Given enough time, the seals in a carb can go bad. A rebuild kit may be what the doctor ordered. But, there may be a way to get your lawnmower started anyway. If you gently tap a carburetor with a hammer or a large wrench, it’ll often free up the stuck needle. If the carb is bad, you will need to have it rebuilt, or order a new one.
Your mower has a relatively simple ignition system, so this section is not going to be very long. It is very common for a fouled spark plug to keep your lawn mower from starting. This can happen at any time, even while the engine is running.
If you are certain that your lawnmower is getting fuel, the next thing that you would want to take a look at would be spark. Spark is much more simple. Take a look at the spark plug. How does is look? If it has caked on carbon build up, sometimes you can get your lawnmower started again just by filing that back off. Really, you need a new spark plug though.
Here’s a fantastic YouTube video on how to determine if a spark plug is fouled:
Inspect the spark plug wire where it meets the boot. If the plug wire looks damaged, or if the boot is cracked, it may be keeping your mower from starting.
The carburetor mixes the air and the fuel together. This is known as the air fuel ratio. If the mixture is off (particularly if it is too lean), you’ll have a really hard time getting the mower to start. If you are sure that you have fuel and spark, the carb is the place to look. This assumes that something is not blocking the air intake (such as an air filter caked with grass clippings).
Other Things that Can Keep a Mower From Starting
While the above section takes a look at what would keep an engine from running, this section deals with what would keep the engine from running.
See Also: The Best Lawnmower for Three Acres
Rodents (mice in particular), love to nest in mowers. Mowers are great at keeping the bad weather out, and have abundant material to build a nest with. Mice will chew on the wiring to sharpen their teeth. If they chew through the right wire, it can be very difficult to tell just by a quick glance at the mower.
If your mower won’t start, it could be a rodents fault. Make sure there isn’t a nest blocking the air intake as well.
Dead Man Switch
A riding mower will not start with the blades engaged. If there is something keeping the blade switch from returning all the way down, it’ll keep the mower from starting in the same fashion that a neutral safety switch would. Try yanking down on the handle while turning the key.
The same principal goes for the dead man on a push mower. Make sure that there isn’t a bunch of extra slack where the cable meets the engine. If there is it may need an adjustment.
Seat Switch (Rider Only)
Just like the Dead Man, you’ll need to make sure that the seat switch isn’t damaged in some way. Most of the time, this switch will keep the mower from even turning over. Make sure that the contact points are clean and rust free.
Conclusion: Lawnmower Not Starting
We hope this guide has helped you get your lawnmower started. If you do get it started, please leave a comment letting us know what the issue was. Thanks for reading!