17 Reasons Why Your Craftsman Lawn Mower Won’t Start

As the owner of a lawn mower, you will most likely come upon a time when your lawn mower doesn’t start and it may be at a time when you need it most.

A Craftsman lawn mower won’t start when the engine is not getting air, fuel, or spark due to a plugged air filter, bad fuel, faulty switches, bad battery, bad spark plug, fuel blockages, or dirty carburetor.

Keep reading for my complete list of items that can prevent your riding mower or push mower from starting.

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Troubleshoot a Craftsman Mower Starting Problem: Fuel, Air, and Spark

An internal combustion engine on a mower requires fuel and air to be introduced to the cylinder. This mixture is compressed and ignited with spark to form combustion.

Check for a Fuel Problem

Old gas is often the root cause for fuel components to stop functioning or for clogs to develop.

Before checking for a fuel problem, if your mower has a fuel shut-off valve, make sure it is in the open position. This valve is often moved to the closed position when the mower is stored or for transportation.

Perform this test to narrow down your problem to the fuel system:

• Detach the air filter cover and remove the air filter.
• Spray carburetor cleaner into the air intake. Find out why I use carburetor cleaner and not starter fluid.
• Attempt to start your mower using the manual recoil starter or turning the ignition key (depending on your mower type)
  • If the mower attempts to start or starts, then you have a problem with the fuel system.
    • The most common fuel issues are a dirty carburetor, clogged fuel filter, and clogged fuel lines. The fuel pump may also be an issue if your mower uses one.
  • If the mower doesn’t attempt to start, you most likely have a spark plug problem.

Check for an Airflow Problem

Air is an important component needed for your engine to start. The engine must run rich to start a cold engine. This condition allows more fuel and less air into the cylinder.

Airflow is controlled by the choke. You will find a choke lever that opens the choke plate to introduce more air and close the choke plate to restrict air.

On newer push mowers, you will find an automatic choke controlled by a thermostat.

Perform this test to narrow down your problem to the air supply system:

• Detach the air filter cover and remove the air filter.
• Inspect the air filter’s condition. A clogged air filter will restrict airflow. Clean the filter or replace it if it is very dirty or damaged.
• With the air filter removed, inspect the choke plate.
  • Manual-choke model
    • Move the choke lever to the on position: The choke plate should be closed.
    • Move the choke lever to the off position (on some models, this is placing the throttle in the fast throttle position): The choke plate should be open.
  • Auto-choke model
    • The choke plate should be closed when the engine is cold and moved to the open position when the engine warms.
• If the choke isn’t opening and closing correction, check the choke linkage and choke cable. Loosen a stuck choke by lubricating the linkages and choke shaft using carburetor cleaner. Replace a bad choke cable (if used on your model).

Check for a Spark Problem

Spark must be released at the right time for combustion. A spark plug may fail to spark if it is dirty or damaged. It may also fail due to a loose spark plug wire, a bad ignition coil (armature), or other ignition system problems.

Perform this test to narrow down your spark problem:

• Remove the spark plug wire (boot) from the spark plug.
• Attach a spark plug tester to the spark plug ignition wire.
• With the spark plug still installed, attach the other end of the spark plug tester to the spark plug.
• Attempt to start the engine using the pull cord or electric start.
• You will see a glow in the transparent section of the tester if it is generating a spark.
• If you don’t see a glow, the spark plug may be bad or you may have a bad ignition coil. On electric start models, you may have a problem with the ignition system including the battery, wiring, and starter solenoid.

Reasons Why Your Craftsman Mower Won’t Start  

1. No Gas in Your Fuel Tank 

Having gas in the gas tank seems like the obvious answer, but it is often overlooked. I’m just mentioning it just in case you forgot to check.  

Fix: Fill with fresh gasoline with an octane level of 87-grade or higher. Choose a gas with an ethanol level no greater than 10%. Find more information on the correct fuel for your gas lawn mower here.  

2. Bad or Old Gas

Gas begins to break down and become less effective after about 30 days. This is why it is important to purchase your fuel from a busy gas station where fuel isn’t sitting around for long periods of time. Only purchase what you can consume within 30 days. 

The ethanol included in gas today is an environmentally friendly substance that works fine in vehicles, but it is not a good choice for lawn mower small engines.

Ethanol attracts moisture and when that moisture evaporates, gummy residue deposits can be left in the fuel system to clog fuel lines, filters, and the carburetor. 

To read more about the correct gas to use in your lawn mower and ways to extend the life of your fuel, read my article about the right type of gas to use in your zero turn, riding mower, or push mower.

Fix: Remove the old fuel, flush the tank, and add fresh fuel. Adding a fuel system cleaner like Sea Foam is a good idea, especially after running old gas through your lawn mower. 

3. Fuel Cap  

Your gas cap has a vent. When this vent gets plugged, the fuel tank forms a vacuum preventing gas from moving through the fuel lines. Your mower acts like it is starved of fuel when it is unable to pull gas due to improper venting of the cap.  

Fix: Try to clean the cap to open up the vent. Replace if your cap is broken or you are unable to get your cap to vent.  

4. Bad Spark Plug or Loose Spark Plug Wire

Another reason your mower won’t start may be due to a bad spark plug connection or a damaged spark plug. An excessively dirty spark plug can foul out causing your engine to misfire.  

Fix: Remove your spark plug and inspect it for signs of carbon buildup or a cracked porcelain insulator. Replace with a new spark plug(s). Make sure to gap them according to the manufacturer’s specifications.  

5. Clogged Air Filter  

Your air filter should be cleaned or changed frequently so your engine can continue to pull in clean air. When airflow is blocked because of a plugged air filter, the engine runs hot and searches for air where ever it can find it including air remaining in the crankcase.

Fix: Clean your paper air filter by removing it from the air filter housing, being careful not to drop any dirt into the intake. Tap the filter against a solid surface to remove excess dirt. 

Hold the filter up to the light to check to see if light can be seen through every area of the filter. If you cannot see light, you must replace the air filter.  

You can find information on other types of air filters here.  

6. Bad Fuel Pump  

When your fuel tank is lower than the carburetor, you will have to pump fuel to the carburetor using a fuel pump. The fuel pump will have three ports: an inlet port, an outlet port, and a port that is connected to a line off of the crankcase that pressurizes the pump.

You may be able to visually recognize your fuel pump is bad by checking the pump for small cracks or fuel leaking. You will have to replace the fuel pump if you see cracks or fuel leaking outside of the pump.

If the fuel pump appears to be in good condition, you need to check the fuel lines to make sure fuel is getting to the fuel pump and fuel is being pumped out of the fuel pump.

Fix:

• Verify you are getting fuel to the fuel pump. Turn off the fuel valve or use a clamp to stop the flow of fuel. (Not every mower has a fuel valve). Disconnect the line from the inlet port of the fuel pump and place it in a container that sits lower than the fuel tank. Unclamp or turn on the fuel valve and check to make sure fuel is flowing out of the tube into the container.
  
  If you are not getting fuel, check the fuel lines or the fuel filter for blockage.
  
  
• Verify your fuel pump is pumping fuel to the carburetor. Reinstall the first fuel line you took off by connecting it to the fuel pump inlet. Remove the fuel line from the carburetor. Place the tube in a container, start the lawn mower, and watch the end of the fuel line to make sure fuel is being pumped out of the fuel line into the container. You should have a steady flow or pulsating flow of fuel coming out of the fuel line.  
  
  Replace the fuel pump if it is unable to consistently pump fuel out of the outlet port.

7. Plugged Fuel Filter  

Your fuel filter strains the fuel coming out of your fuel tank and running through your fuel system to keep out any dirt or debris. Old fuel can leave gummy deposits when it evaporates, which may plug the fuel filter.

Fix: A fuel filter that is cracked must be replaced. You can check whether fuel is being passed through the filter by removing the fuel line after the fuel filter and placing it in a container to see if you have fuel flow.

Use a clamp to stop fuel flow while you are moving the line into the container and then remove the clamp to test flow. Replace a fuel filter that doesn’t allow fuel to pass through.

8. Blockage in the Fuel Line  

Old fuel that gummed up can become lodged in your mower’s fuel line.   

Fix: Remove the fuel line. Next, you need to spray a carburetor cleaner into the tube and use compressed air to blow air through the tube until the line is no longer clogged. You can also replace it with new fuel line.  

9. Clogged & Dirty Carburetor  

The carburetor is an essential component of your Craftsman lawn mower. Its function is to make sure your engine receives the right mixture of gas and air to create a combustion in the engine.

Without this correct ratio of gas and air, your lawn mower may run rough and may not be able to start.

Fix: Your carburetor can be replaced or cleaned. Most of the time, cleaning your carburetor will do the job, and your lawn mower will be up and running again. You can find steps for cleaning your carburetor in this article. 

10. Bad Battery, Loose Cables or Corroded Terminals

To continue to check for your starting issue you will need to check the battery, cables, and terminals. The battery must be charged at a reading of 12.7 volts or greater. Loose cables and corroded terminals can contribute to starting issues.

Fix: Clean corroded terminals in a baking soda solution containing 2 cups of water and 3 rounded tablespoons of baking soda. Use a wire brush to scrub the terminals clean.

Test your battery with a multimeter. If you receive a reading of less than 12.7 volts, you must charge your battery. Read more about the steps and items needed to charge your battery here. If your battery does not hold a charge, you will need to replace it with a new battery.

You can purchase lawn and garden batteries at hardware and auto parts stores. Many stores that sell batteries will charge you a core fee if you don’t have the bad battery to give them. Don’t forget to bring your battery with you.

11. Bad Safety Switch  

A mower uses several safety switches in order to keep you safe when you are operating the lawn mower. These switches can become faulty and cause your lawn mower to not start. 

Fix: Test the switch using a multimeter or you can temporarily bypass the safety switch to identify a bad switch. Do not operate a mower without the safety switch installed for your safety.  Always have safety switches installed and working on your equipment.

12. Bad Ignition Switch  

You insert the key into your ignition switch and turn it only to find your mower doesn’t start or even turn over. The ignition switch could be the problem.

Fix: You can use a multimeter to test the ignition switch. Replace the switch if bad.

13. Bad Recoil on a Push Mower 

Many push mowers are pull-started using a recoil. When that recoil is damaged or the parts fail, the mower is no longer able to be started using the recoil. A bad pulley, broken spring, or broken clips are likely to be the culprit of a broken recoil.

Fix: You can attempt to replace the spring and restring the recoil. If it does not work because other components in your recoil are damaged such as the clips or pulley, you are better off just replacing the recoil assembly.

14. Bad Ignition Coil  

The ignition coil provides voltage to the spark plug so it can fire and start the engine. The engine will not start if the spark plug isn’t able to fire.   

Fix: After you verified your spark plug is in good condition, check the continuity of your ignition coil using a multimeter. Replace the ignition coil if you find a break in the continuity.  

15. Bad Starter Solenoid

A lawn mower solenoid is an electromagnetic switch that is like an on-off switch that actuates the starter motor to turn over the engine. A click or hum when turning your ignition key is an indication to check your solenoid.

Another indication your riding mower solenoid may be bad is when a wire attached to your solenoid gets hot and begins to smoke or melt.

Fix: Test your Craftsman mower solenoid by following the steps here. Replace your solenoid if it is found to be bad.

16. Faulty Charging System  

While the charging system isn’t the main reason your mower won’t start, it can contribute to a weak battery that prevents the mower from starting.

When the charging system fails to charge the battery, the battery may not be able to start the mower the next time you go to use it.

A bad stator or alternator can be the problem along with several other electrical parts. Read this article to test your charging system here using an ohmmeter. 

Fix: If you find the problem is in your charging system, have a small engine mechanic identify what is the actual cause of the failure. It could be several different items and you will just be guessing at the problem which gets pretty expensive.  

17. Incorrect Starting Procedure

There are specific instructions for starting different types of Craftsman mowers. A reason these specific procedures are put in place is for safety reasons. For example, push mowers to use a safety bar to recognize the operator.

Riding mowers use a seat switch to confirm the operator is still on the mower. They also use a brake switch that can fail to allow the mower to start if the brake is not engaged. 

Fix: Refer to your operator’s manual to ensure you are operating your lawn mower correctly, so you don’t set off the safety features that shut off your lawn mower. 

Related Items

Mower Stops Running

Many items that prevent a lawn mower from starting are also reasons why your mower may die when cutting your lawn. There are additional items to check if you are experiencing this problem check out this article on why your mower may die.

Mower is Smoking

Another problem you can encounter is smoking. Smoking occurs when other substances burn in your fuel system or the engine gets hot and begins to burn oil. Find more information in “Why Your Craftsman is Smoking“.