It won’t start if there is a plugged air filter, old fuel, a dirty carburetor, clogged fuel lines, a faulty gas cap, a plugged air filter, a faulty safety switch, a dead battery, or a faulty starter solenoid.

Learn more about items that could prevent your mower from starting. Following the safety precautions in your operator’s manual will keep you safe when working on your mower Your Walk-Behind Mower Won’t Start.

Taking your lawnmower out of your garage, you find that it won’t start when you’re mowing. If you are able to diagnose the problem, there’s often a quick and easy fix. Low fuel, spark plug issues, a clogged carburetor, a broken clutch, and broken gears are some of the common lawn mower problems.

Reasons Your Walk-Behind Mower Won’t Start 

Your Walk-Behind Mower Won’t Start

Powered walk-behind mowers need gas. Mower owners know this.

It occurs to me often that when you’re frustrated with the mower not running, you skip the obvious things like gas Your Walk-Behind Mower Won’t Start.

A gas tank needs fuel. Add fresh fuel.

Walking-Behind Mower Gas Cap Won’t Vent

Gas caps on walk-behind mowers come with a vent to equalize the air pressure in the fuel tank.

Plugging the vent will create a vacuum inside the fuel tank, which prevents fuel from leaving. Fuel will not get to your engine and the mower will not start.

To check whether your gas cap is venting, remove the cap and see whether the lawn mower starts. Place the cap back on the fuel tank and let it continue to run.

If a restriction is placed on your fuel supply, your mower may eventually sputter and shut down. That means you likely have a faulty gas cap.

Replacement of your gas cap is the solution if your gas cap will not vent correctly. Occasionally, cleaning it can help remove a clog, but it isn’t always effective.

A gas shot test

To find the problem quickly, narrow down the search area. Gas shot tests are the most common method of diagnosing non-starting mowers. Think of this as an elimination round. During the test, the fuel system and ignition system are simultaneously tested without bypassing the fuel system.

Remove the air filter. Fresh gas is needed. Fresh gas will fail this test. Fill a bottle cap with gas and drop it into the carburetor. Make sure the choke is full when starting the mower.

Fuel shot – Use clean fresh fuel. Pull off the cover and air filter (some are fixed on with screws or wing nuts, others just pull off)

With brand-new carburetors, you won’t be able to fuel up the carburetor without the hassle of inserting the spark plug directly into the cylinder, using a funnel, and pouring gas into the cylinder.

Mower Spark Plug or Connection Problems 

Walk-behinds cannot start and run without a spark. It can become dirty with carbon buildup.

Intermittent starting problems can also be caused by improper spark plug gapping.

Your spark plug(s) can fail if they are dirty from carbon buildup or have a broken porcelain or burned electrode. Your walk-behind mower may also experience starting problems if your spark plug is incorrectly gapped and does not make a proper connection.

Look for carbon buildup, cracked porcelain, or burnt electrodes when removing the spark plug.

In case of any of these conditions, replace the spark plug. Spark plugs should be gapped accurately and wires secured.

Use a wire brush to remove carbon buildup from a spark plug if it’s still in pristine condition and only slightly dirty.

You have a faulty solenoid on your mower

A starter solenoid that doesn’t function properly can cause the mower to not start. In walk-behind mowers, the solenoid is an electromagnetic switch that actuates the starter motor.

If your ignition key clicks or hums, check your solenoid. It is also possible that your mower’s solenoid is damaged if a wire attached to it gets hot and smokes.

Find out if your lawn mower solenoid is damaged in our article “How To Tell”.

Replacement of your solenoid is the most effective solution.

 Conclusions

You can be extremely frustrated when you keep pulling the lawn mower starter cord, and then hear the motor sputter and die. You may be tempted to take the lawn mower to a repair shop or even leave it by the curb for bulk trash pickup. However, you can possibly fix it yourself if it’s a simple repair Your Walk-Behind Mower Won’t Start.

Before opening your wallet, put these easy and cheap fixes to the test. You don’t have an excuse not to mow with a broken lawnmower if one of these fixes helps. Back out there and shape up your grass!