There’s nothing more frustrating than pulling the starter cord on a crisp morning, expecting your Craftsman mower to roar to life, only to be met with silence or sputtering. Often, the culprit behind this stubborn behavior is a small but critical component: the auto choke. When this system fails, it disrupts the delicate fuel-to-air mixture your engine needs to start cold. If you’re facing the common issue of a Craftsman lawn mower auto choke not working, how to fix it is probably your top priority.
The auto choke, or automatic choke system, is designed to make starting your mower effortless. It automatically enriches the fuel mixture when the engine is cold and gradually leans it out as the engine warms up. When it malfunctions, you’re left to do its job manually, which is a guessing game at best. Fortunately, many of the fixes are within reach for a DIY enthusiast.
What Does the Auto Choke Actually Do?
Think of the auto choke as the engine’s personal assistant for cold starts. Inside the carburetor, a small plate called the choke butterfly valve restricts airflow. This creates a richer fuel mixture, which is exactly what a cold engine craves to ignite. On most modern Craftsman mowers, this valve is controlled by a thermostatic spring that expands and contracts with heat. When the engine is cold, the spring is tight, holding the choke closed. As the engine warms up, the spring expands, slowly opening the choke valve to a normal running position.
Diagnosing a Craftsman Lawn Mower Auto Choke Not Working, How to Fix
The first step is always a simple visual inspection. Locate the air filter cover and remove it to access the carburetor and choke linkage. You should see a mechanism connected to the choke plate. Now, look for the thermostatic spring—it’s often a small, coiled piece of metal. Gently move the linkage with your finger. The plate should snap back to a closed position when released if the engine is cold. If it feels loose, sticky, or doesn’t move at all, you’ve found a problem area.
Common Culprits and Their Simple Solutions
More often than not, the issue isn’t a broken part but a dirty or disconnected one. Here are the most common problems and their straightforward fixes.
A Dirty or Gummy Choke Mechanism
Over time, old fuel residue and grass clippings can create a sticky varnish on the choke plate shaft and linkage. This gunk prevents the plate from moving freely. A thorough cleaning with carburetor cleaner can often restore perfect function. Simply spray the linkage and the plate shaft, working the mechanism back and forth until it moves smoothly.
A Disconnected or Misadjusted Linkage
The auto choke system uses a series of small rods and springs. It’s not uncommon for a spring to pop off or a linkage rod to become bent, especially if you’ve hit something while mowing. Carefully trace the path of the linkage from the thermostatic spring to the choke plate. Ensure all springs are connected and that the rods move freely without binding. A small pair of needle-nose pliers is perfect for reattaching a spring.
A Failing Thermostatic Spring
If the linkage is clean and connected but the choke plate still doesn’t snap shut when cold, the thermostatic spring itself may have lost its tension or broken. This part is specific to your engine model (commonly Briggs & Stratton or Kohler), but it is usually inexpensive and relatively easy to replace. You’ll need to note your mower’s model number to find the correct replacement part.
Getting Back to a Smooth Start
Dealing with a faulty auto choke can feel like a major setback, but as you’ve seen, the solution is often simpler than it appears. By methodically checking for dirt, disconnected parts, and a weak spring, you can usually diagnose and resolve the problem yourself. A little cleaning or a small, inexpensive part is typically all it takes to restore your Craftsman mower’s reliable, one-pull starting power and get your lawn looking great again.