There’s a special kind of frustration that comes with a lawn mower that starts on the first or second pull, only to sputter and die a few seconds later. You get a brief moment of hope, followed by the silence of a job still waiting to be done. This particular issue is a common headache for many homeowners, and it almost always points to a simple, fixable problem.
If your lawn mower starts but does not stay running, you’re likely dealing with an interruption in one of the engine’s core needs: fuel, air, or spark. The good news is that you don’t need to be a small engine mechanic to diagnose and often fix the issue yourself. By understanding a few common culprits, you can get back to a neatly trimmed lawn without the hassle or expense of a service call.
Lawn Mower Starts But Does Not Stay Running: Common Causes
Let’s walk through the most frequent reasons a mower cuts out shortly after starting. These are listed in order from the easiest and most common to the slightly more involved, making it simple for you to troubleshoot step-by-step.
A Clogged Carburetor is Often the Culprit
This is, by far, the most common reason for a mower that starts and then dies. The carburetor’s job is to mix fuel and air in the perfect ratio for combustion. Today’s gasoline, especially gas with ethanol, can leave behind sticky varnish and gums that clog the carburetor’s tiny internal passages. When you first start the mower, the choke is on, providing a rich fuel mixture. Once the engine warms and the choke opens, the engine relies on those tiny passages for fuel. If they’re clogged, the engine starves for fuel and stalls. Old fuel left in the tank over the winter is a primary cause of this issue.
Check Your Fuel Flow and Cap
It may seem too simple, but a faulty fuel cap is a classic cause of this problem. Modern fuel caps have a small vent that allows air to enter the tank as fuel is used. If this vent becomes blocked, a vacuum lock forms inside the tank, preventing fuel from flowing to the carburetor. A quick test is to loosely screw the cap back on and start the mower. If it stays running, you’ve found your issue. Similarly, a clogged fuel filter or a kinked fuel line will restrict the flow of gasoline, causing the engine to die once the fuel in the carburetor bowl is used up.
When a Dirty Air Filter Causes Problems
Your mower’s engine needs a precise mix of fuel and air to run. A severely clogged air filter can choke off the engine’s air supply. This creates an overly rich fuel mixture, which can cause the engine to start but quickly flood and stall, especially once it comes off the initial choked setting. It’s a good practice to check your air filter at the start of each mowing season and clean or replace it as needed.
Other Potential Issues to Consider
If the simple fixes don’t solve the problem, there are a couple of other areas to consider. On some mowers, a faulty ignition coil can fail once it heats up, causing the spark to die and the engine to stall. This is less common but becomes more likely if your mower runs for a minute or two before cutting out. Additionally, if your mower has a built-in safety feature like a seat switch or blade engagement switch, a loose connection could be intermittently killing the engine.
In most cases, the solution to a lawn mower that starts but won’t stay running lies within the fuel system. By starting with fresh gas and investigating the carburetor, fuel cap, and air filter, you can usually pinpoint the problem. A little bit of focused troubleshooting can save you time and money, getting your mower back to reliable operation for the season ahead.