There’s nothing more frustrating than getting your Craftsman lawn mower started, only to have it sputter and die a few seconds later. You pull the cord again, it starts, and then the cycle repeats. This common problem can turn a simple lawn care task into an all-day ordeal. Before you resign yourself to an expensive repair bill or a trip to the big box store for a new mower, take a deep breath. The solution is often simpler than you think, and with a few basic tools and a little patience, you can often solve the issue yourself. This guide will walk you through the most common reasons and provide clear steps on how to fix a Craftsman lawn mower that won’t stay running.
The good news is that most small engine problems, especially those related to inconsistent running, stem from just a few key areas. Your mower needs three things to run smoothly: clean air, fresh fuel, and a strong spark. When one of these elements is compromised, the engine can’t maintain its rhythm. By systematically checking these systems, you can usually pinpoint the culprit without needing advanced mechanical skills. Let’s look at where to start your troubleshooting journey.
Start with the Fuel System
More often than not, a mower that won’t stay running has a fuel-related issue. The most common culprit is old or contaminated gasoline. Gasoline begins to degrade in as little as 30 days, forming a sticky varnish that can clog the tiny passages in the carburetor. If your mower has been sitting with fuel in it over the winter, this is the first place to look.
Begin by safely draining the old fuel from the tank and replacing it with fresh, clean gasoline. If the problem persists, the next step is to check the fuel line for cracks or blockages and inspect the fuel filter (if your model has one). For many, the final step in this process is cleaning the carburetor. This might sound intimidating, but with a carburetor cleaning spray, it’s a very manageable task. Spray the cleaner into the carburetor’s air intake and jets to dissolve any gunk that’s preventing a steady fuel flow.
Checking the Air Flow
Just like a fire needs oxygen, your mower’s engine needs a steady stream of clean air to mix with the fuel. A clogged air filter can starve the engine, causing it to run poorly and shut down. Locate the air filter housing—it’s usually a black plastic box on the side of the engine—and remove the cover.
Take out the air filter and hold it up to the light. If you can’t see light passing through it, it’s time for a replacement. If it’s a foam filter, you can wash it in warm, soapy water, let it dry completely, and then apply a light coat of fresh filter oil before reinstalling. A clean air filter is a simple and inexpensive fix that can make a world of difference.
How to Fix a Craftsman Lawn Mower That Won’t Stay Running by Looking at the Spark
If your fuel and air systems are in good shape, the next component to check is the spark plug. A worn or fouled spark plug can produce a weak spark, making it difficult for the engine to run consistently. Carefully disconnect the spark plug wire and use a socket wrench to remove the plug.
Inspect the electrode at the end of the plug. It should be a light tan or gray color. If it’s black with soot or has a burned, eroded electrode, it needs to be replaced. When you get a new plug, make sure it’s properly gapped according to your owner’s manual’s specifications before screwing it in snugly by hand and giving it a final gentle tighten with the wrench.
Don’t Forget the Simple Safety Switches
Modern Craftsman mowers have several safety switches that can interrupt the engine if they are not engaged. The two most common are the operator presence lever (the “dead man’s” handle you hold down) and the blade engagement switch. If the mechanism that holds the handle in place is loose or out of adjustment, the mower’s engine will be intentionally shut off. Check that all control cables are connected and moving freely.
By methodically checking the fuel, air, and spark systems, you’ve tackled the vast majority of issues that cause a mower to stall. Remember to always prioritize safety by disconnecting the spark plug before performing any maintenance. With a little troubleshooting, you can have your Craftsman mower running smoothly again, saving you time and money.