16 Reasons Your John Deere Lawn Mower Won’t Start 


It’s usually bad timing when your John Deere mower won’t start. You can bring your lawn mower to the John Deere dealership to be fixed, but in the heat of the season, you may not get your lawn mower back for a week or two. Your lawn doesn’t stop growing so what can you do?

A John Deere lawn mower may not start because of an issue in the fuel system; a clogged air filter; a dirty carburetor; or a bad battery, safety switch, spark plugs or ignition switch. A faulty charging system and ignition coil can also be the culprit of your starting problem. 

I have put together a complete list of items that can cause starting issues in your John Deere gas powered lawn mower. Many of these items can be checked and fixed in no time so you can have your lawn looking good in no time!

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Reasons Why Your John Deere Mower Won’t Start 

1. No Gas in Your John Deere Fuel Tank 

This may seem like a no brainer, but to my surprise, I have found it to be the reason why several of my customers’ mowers wouldn’t start. Sometimes you forget the simple things.

Fix: Fill with fresh gasoline. I write more about the correct fuel for your gas lawn mower hereOpens in a new tab.

2. Bad or Old Fuel in Your John Deere

Fuel that doesn’t get used right away becomes old and stale over time. Gas only has a 30 day shelf life before it begins to break down and become less effective. The ethanol added to today’s gasoline tends to draw moisture to the fuel. When this moisture evaporates, a residue is left behind that clogs the fuel system. 

Always use fuel right away.  If you are unable to consume the fuel within 30 days, you need to add a fuel additive to stabilize the fuel

Fix: Remove the old fuel, flush the tank and add fresh fuel. 

3. Faulty John Deere Fuel Cap 

Your fuel cap is vented by design.  When your cap is broke and the cap no long vents, a vacuum is formed in the fuel tank and your lawn mower is no longer able to get fuel. 

Fix: Replace with a new fuel cap. You can find one on AmazonOpens in a new tab. or visit your local John Deere dealership. 

4. John Deere Mower has a Bad Spark Plug or Loose Connection 

You may have a bad spark plug connection or the spark plug may be damaged. A plug that is excessively dirty can foul out causing your engine to misfire. Remove your spark plug and inspect it for signs of carbon buildup or a cracked porcelain insulator. A loose connection or a plug that isn’t gapped correctly can also cause starting issues.

Fix: Replace with a new spark plug(s). Make sure to gap them according to your manufacturer’s specifications. 

5. John Deere Air Filter is Plugged

Clean air is crucial to the performance of your John Deere’s engine. When you air filter is excessively dirty, the engine can’t get air and it is essentially being suffocated. This can develop into a larger problem causing extensive engine damage if not addressed right away. 

Fix: Clean your paper filter by removing it from the air filter housing. Be 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. 

For information on other types of air filters read my article hereOpens in a new tab.

6. Bad John Deere Fuel Pump 

You need to make sure fuel running through one inlet port of the fuel pump is pumped to the outlet port. If you don’t see fuel coming out of the outlet port, your John Deere fuel pump may be bad. 

A fuel pump is used to pump gas to your carburetor when the fuel tank sits lower than the carburetor. The fuel pump has 3 ports on it. There is an inlet port and outlet port where the fuel passes into and out of the pump. The third port is attached to a fitting on the crankcase which pressurizes the fuel pump. 

FIX: First, inspect your vacuum fuel pump for cracks. If you see fuel outside of the fuel pump or cracks in pump, the pump will no longer being able to create the pressure needed to pump fuel. 

Second, you will want to make sure you are getting fuel from the fuel tank to the fuel pump. Turn off the fuel valve or use a clamp to stop the flow of fuel. Disconnect the line from the fuel pump inlet port and place 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, your fuel troubles exist before the fuel pump. You will want to check for blocked fuel lines or a plugged fuel filter. 

Third, if your fuel pump appears to be in good condition, and you have verified you are getting fuel to the fuel pump, you will need to 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 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 your fuel pump if it fails to provide a flow of fuel out of the outlet tube or if you find fuel pump cracks or leaks. 

7. Plugged John Deere Fuel Filter 

Look at the fuel lines running in and out of your fuel filter. Make sure the fuel that is running into the filter using the same steps used when identifying fuel flow from the tank to the fuel pump above. Check for cracks in the fuel filter.

Fix: Replace with a new fuel filter if needed.

8. Blockage in the Fuel Line 

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

Fix: Remove the fuel line, spray carb cleaner into the tube and use canned air to blow air through the tube until the line is free of debris and gummy residue. You can also replace with new fuel line if you are unable to remove the clog or if your fuel lines are dry, brittle and beginning to crack.

9. Clogged & Dirty John Deere Carburetor 

The carburetor is essential to your engine running because it regulates the amount of air mixed with the right amount of fuel to create a combustion. The John Deere lawn mower carburetor and its components can get dirty and gum up which affect how it regulates the air and fuel mix.

Fix: Clean the carburetor by taking it apart and using carb cleaner to clean the carburetor including the float bowl and needle. You can find steps for cleaning your carburetor in this articleOpens in a new tab.

You may choose to replace the carburetor if it appears to be in very bad condition. 

10. John Deere Has a Bad Battery or Loose Terminals 

Your John Deere lawn mower won’t start when the battery is dead. Make sure your battery cables are secure and the connections are not showing signs of corrosion. 

Fix: Test your battery with a multimeterOpens in a new tab.. You will want a reading of about 12.7 volts. Place on a charger to charge your battery if your reading is less than 12.7 volts. 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. 

11. Bad John Deere Safety Switch

Your lawn mower may use several safety switches in its operator’s presence control system. The switches are designed to kill the engine if the operator leaves the seat. A bad switch can cause your John Deere mower not to start. 

Fix: You can temporarily bypass the safety switch to identify a bad switch. A multimeter can also be used to help identify a bad switch. Never operate a mower without a good safety switch or when the switch is bypassed. Many people get injured by mowers annually by rolling them or falling off the mower.  Always have safety switches installed and working on your equipment.

12. John Deere Has a Bad Ignition Switch 

You insert the key into your ignition switch and turn it only to find nothing happens. Your John Deere mower won’t start. The ignition switch can be the culprit.  You can check the switch using a multimeter.

Fix: Replace Switch if you find it is bad

13. Bad Ignition Coil on Your John Deere Mower

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 ohm meter. Replace the ignition coil if you find a break in the continuity. 

14.Bad Starter Solenoid on Your John Deere Mower

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

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

15. John Deere Mower’s Charging System is Not Charging 

The charging system can drain the battery and cause your lawn mower not to start. A bad stator or alternator can be the problem among other things. I show steps on how to test your charging system hereOpens in a new tab. using an ohm meter. 

Fix: If you find the problem is in your charging system, have a small engine mechanic identify the actual cause of the failure. It could be several different items and you don’t want to start guessing at the cause of the problem. Throwing parts at your John Deere mower gets pretty expensive. 

16. Incorrect Operating Procedure When Starting Your John Deere 

There are different safety procedures taken by John Deere when starting and operating your lawn mower that will shut off the mower. For example, when you get off your zero turn mower with the engine still running, your mower will shut off if you fail to set the parking brake first.   

Fix: Refer to your John Deere operating 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. 

My top items to keep on hand to service & troubleshoot your lawn mower

Socket & Allen Wrench SetOpens in a new tab. – Tool set needed to service & troubleshoot your mower problemsCarburetor CleanerOpens in a new tab. – Clean clogs & buildup in fuel system
MultimeterOpens in a new tab. – To check voltage, continuity & current to identify electrical problemsFuel StabilizerOpens in a new tab. – Stabilize & clean your fuel to minimize fuel system buildup
12-Volt Battery ChargerOpens in a new tab. – Battery/trickle charger to start your mower & slowly charge your batteryFilter WrenchOpens in a new tab. – Helps loosen your filter
Oil Drain PanOpens in a new tab. – To collect oil with spout to place in containers for disposalBattery Powered InflatorOpens in a new tab. – Keep your lawn mower tires inflated to prevent uneven cutting or steering issues

Powered Equipment Team

We're just a guy and a girl obsessed with outdoor power equipment! We are excited to share the knowledge and tips we have learned over our combined 55 years in the power equipment industry. We have both ran equipment dealerships and took pleasure in helping our customers everyday providing equipment repair, parts, purchasing, and business tips to our residential and commercial clients. We hope our blog will help you with your next purchase, repair, or project.

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