15 Reasons a John Deere Lawn Mower Won’t Start (Lawn Tractor & Zero Turn)

by Jack Grover
John Deere mower
Reading time: 22 min Prefer to listen?

Your John Deere mower is a reliable partner in keeping your lawn in top shape, but when it suddenly refuses to start, you may find yourself in quite a predicament.

With the busy season upon us, taking your mower to the dealership for repairs could mean waiting weeks before getting it back — and grass doesn’t stop growing just because your mower is out of commission.

So, what can you do to get your trusty John Deere mower up and running again? Thankfully, there are several things you can check and troubleshoot before resorting to professional help.

From safety switch malfunctions to spark plug problems, here is a list of the most common issues and ways to solve them.

Quick Reference Chart

Potential CausesSolutions 
No Gas in the TankFill up the tank with sufficient fuel.
Clogged Fuel FilterClean or replace the fuel filter.
Bad or Old FuelDrain old fuel, clean the carburetor, and fill up with fresh gasoline (preferably mixed with a stabilizer).
Faulty Fuel CapInspect for damage, check the vent, and replace it if necessary.
Bad Fuel PumpTest fuel lines, replace the fuel filter, and buy a new fuel pump if necessary.
Loose Spark Plug WireEnsure the wire is securely connected to the spark plug.
Dirty or Damaged Spark PlugClean or replace the spark plug.
Dirty CarburetorDisassemble and clean the carburetor using a designated cleaner.
Faulty CarburetorReplace the entire carburetor.
Dead BatteryCheck battery connections, test the battery, and replace it if necessary.
Bad Ignition SwitchReplace the ignition switch.
Safety Switch MalfunctionsTest and replace the faulty seat switch, blade engagement switch, or parking brake switch as needed.
Clogged Air FilterRemove, clean, or replace the air filter.

Please note that this chart is intended as a quick reference guide only. Consult your owner’s manual for specific troubleshooting techniques, and always exercise caution when working on your lawn mower.

Fuel System Issues

When it comes to engine problems, fuel system issues are some of the most common culprits. They can bring your mowing activities to a screeching halt, leaving you scratching your head and wondering where to start.

A well-functioning fuel system is crucial for any engine-operated machinery, and lawn mowers are no exception. Identifying and addressing these issues can save you from unnecessary frustration and prevent further complications down the line.

No Gas in the Tank

First things first, before jumping to conclusions or getting too concerned, take a moment to check if there’s sufficient fuel in the tank.

At times, something as simple as an empty tank can be the root of your lawn mower problems. If it’s running low, simply filling up might do the trick.

ful tank

With enough fuel to power the engine, you could be back to mowing in no time, enjoying the satisfaction of a freshly trimmed lawn.

However, if you have enough gas and your mower still isn’t starting, it’s time to delve deeper into potential fuel system issues.

Clogged Fuel Filter

One key component to examine is the fuel filter. This small but vital part plays a critical role in ensuring a clean and efficient fuel supply for your mower’s engine.

Over time, debris and contaminants can build up within the filter, obstructing fuel flow and causing your mower to struggle when starting. In cases like this, cleaning or replacing the fuel filter can help get your John Deere lawn mower back on track.

To clean the filter, carefully remove it from the mower and use compressed air or a soft brush to remove any debris.

If cleaning doesn’t solve your problem or the filter appears damaged, consider replacing it with a new one.

Bad or Old Fuel

Gasoline, unlike fine wine, doesn’t age gracefully. As time ticks away, it undergoes a slow but steady transformation that ultimately wreaks havoc on your mower’s engine.

When left sitting for months, volatile components within the fuel evaporate, leaving behind a thick, gummy residue. A substance that was once a powerful propellant now threatens to clog your carburetor and render your mower lifeless.

“But wait,” you might say, “my John Deere ran just fine last season!” True, but even the most reliable machines can fall victim to old fuel’s insidious grasp.

Consider this: gasoline begins to degrade after just 30 days. It means the fuel resting in your tank all winter long has slowly transformed into a sticky sludge, ready to bring your mowing adventures to a grinding halt.

If you confirm it is the root of your starting problems, drain the remaining old fuel from the tank and dispose of it safely. Then, give your carburetor a thorough cleaning to eliminate any lingering gunk. Finally, fill up with fresh gasoline — preferably one mixed with a stabilizer — and revel in the sweet sound of a smoothly running engine.

To prevent future fuel-related mishaps, make it a habit to empty your John Deere’s tank before storing it away for extended periods. A simple act that takes minutes can save you hours of frustration and costly repairs.

Faulty Fuel Cap

The fuel cap may seem inconsequential, but it plays a vital role in maintaining proper pressure within the gas tank.

When functioning correctly, this unassuming piece allows air to flow in while preventing fuel vapors from escaping. At the same time, when the cap’s vent becomes clogged or damaged, it can throw a wrench in that delicate balance.

So how does a faulty fuel cap stop your beloved John Deere from roaring to life? The answer lies in the vacuum created by an unvented gas tank.

As fuel is drawn from the tank during operation, air must replace it to maintain equilibrium. A blocked vent prevents air from entering, resulting in negative pressure that starves the engine of its much-needed gasoline.

Identifying and remedying a faulty fuel cap is as simple as following these steps:

  1. Inspect for Damage: Examine your fuel cap for cracks or signs of wear that could compromise its integrity.
  2. Check the Vent: Ensure the tiny hole on top of the cap is clear of debris or obstructions.
  3. Test & Replace: If issues persist after cleaning and inspecting the cap, consider investing in a replacement.

Bad Fuel Pump

The fuel pump transfers fuel from the tank to the engine, providing that essential lifeblood for your mower’s roaring performance. But when the fuel pump turns treacherous, your mower might just give up the ghost.

fuel pump

So, how do you know if a bad fuel pump is the culprit behind your mower’s sudden demise? Look out for these telltale signs:

  1. Sudden power loss: If your John Deere mower loses power while operating, only to regain it momentarily before quitting altogether, a faulty fuel pump could be starving your engine of its much-needed sustenance.
  2. Engine sputters and stalls: An erratic fuel supply caused by a failing pump can result in your engine stuttering or stalling unexpectedly. This situation can leave you with an uneven cut or, worse, stuck halfway through the job!
  3. No-start condition: Sometimes, a bad fuel pump will refuse to cooperate from the get-go. Your faithful beast simply won’t start despite your best efforts, leaving you scratching your head and cursing under your breath.

And here is a list of the best ways to conquer this insidious foe:

  1. Inspect and test: Check your fuel lines and connections for leaks or damage. You can also test the fuel pump by disconnecting the fuel line from the carburetor and turning the engine over. If little or no fuel comes out, it’s time to replace that dastardly pump.
  2. Fuel filter fiasco: A clogged fuel filter can mimic the symptoms of a bad pump. Make sure you replace it regularly to avoid any unnecessary heartache.
  3. The last resort — replacement: If all else fails and your fuel pump is truly beyond salvation, it’s time for a transplant. Replacing it with a fresh, new pump will breathe life back into your John Deere mower and send you back on your merry mowing way.
  4. Preventative care: To keep your fuel pump in excellent shape, make it a habit to use fresh, high-quality fuel and store it properly. Regular maintenance checks will also go a long way in ensuring your mower remains the envy of the neighborhood.
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Spark Plug Problems

The spark plug is an essential component of your mower’s engine. As the primary catalyst for igniting the fuel-air mixture, it initiates combustion, allowing the engine to power up and run smoothly.

When this vital component malfunctions, it can lead to starting issues and adversely impact your mower’s efficiency. Besides preventing your mower from starting, a faulty spark plug may cause other problems, such as poor fuel economy, reduced power output, and engine misfires.

Loose Spark Plug Wire

Begin by taking a look at the spark plug wire. Ensure it’s securely connected to the spark plug, as a loose or disconnected wire can impede proper functioning.

If the wire appears to be in good shape and properly attached, proceed to inspect the spark plug itself.

Dirty or Damaged Spark Plug

To assess the spark plug’s condition, remove it from the engine and carefully examine it, paying attention to any indication of corrosion or fouling. Gently remove debris buildup using a wire brush, and set the electrode gap according to your lawn mower’s specifications.

Additionally, look for visible signs of wear or damage. This may include cracks in the ceramic insulator, damaged electrodes, or deposits caused by oil, carbon, or fuel.

If your spark plug is visibly worn out or damaged, it’s time to replace it with a new one. Keep in mind that experts recommend replacing spark plugs periodically as part of regular maintenance, typically every 100 hours of operation or once per mowing season.

Carburetor Complications

Your lawn mower’s carburetor is responsible for mixing the right proportions of air and fuel to achieve combustion. Still, like any other engine part, the carburetor is susceptible to wear and tear over time.

Dirt, debris, and the occasional buildup of gunk can all lead to malfunctions and negatively impact your mower’s performance.

If you suspect your carburetor might be at the root of your mower’s issues, there are several steps you can take to address the problem.

Dirty Carburetor

One of the first things to try is cleaning your carburetor with a designated cleaner. This specially formulated solution removes dirt and deposits that may have accumulated inside the component.

To perform the task effectively, you’ll need to disassemble the carburetor according to the manufacturer’s instructions, clean each part with the cleaner, and reassemble it.

Faulty Carburetor

In some cases, cleaning may not be enough to resolve the issue.

Replacing the entire carburetor might be necessary if your mower still refuses to start or exhibits poor performance after a thorough cleaning.

You can purchase a new carburetor from a reliable retailer or ask a professional mechanic to help you find a suitable replacement.

That being said, replacing a carburetor can be a complex task, particularly if you lack experience with engine repairs. Because of that, it’s often best to seek the assistance of a qualified mechanic who can diagnose and fix the problem.

Dead Battery

If your John Deere lawn mower is equipped with an electric starter, a drained battery could be the reason for your troubles.

The first thing you should do is to check the battery connections. They should be clean and securely fastened. Dirty or loose connections can hamper the flow of electricity from the battery to the starter, making it seem like the battery is dead when it might not be.


If everything looks good with the connections, it’s time to test the battery. You can do this using a voltmeter or taking it to a local auto parts store offering free battery testing.

If your battery turns out to be dead, it’s time for a replacement.

Remember that batteries can lose their charge over time, especially during long periods of inactivity, such as throughout the winter months when lawn mowing is not required. This loss of charge can lead to a weakened or completely dead battery when you’re ready to begin mowing again.

To avoid this issue in the future, invest in a trickle charger. This device is designed to maintain your battery’s charge throughout periods of inactivity by providing a slow, steady flow of electricity. It will help keep your battery charged and ready for action whenever you need it.

Bad Ignition Switch

The ignition switch is the gatekeeper of your mower’s engine, controlling the flow of electricity from the battery to the starter. When it works seamlessly, your mower leaps into action like an eager lion. But when it goes rogue, it becomes a silent saboteur, leaving you stranded in a sea of grass.

Here are telltale signs your John Deere has become a victim of a bad ignition switch:

  1. Playing Dead: If turning the key results in no response (i.e., no clicks, no whirring), the ignition switch could be the villain in this story.
  2. Flickering Lights: When your mower’s headlights or dashboard lights flicker or fade when turning the key, it indicates an internal issue with the switch.
  3. Hot to the Touch: After attempting to start your mower, touch the ignition switch (carefully!). If it feels unusually warm or hot, there might be an electrical issue at hand.
  4. The Key Conundrum: Is your key refusing to turn smoothly or getting stuck in the ignition? It could be a sign that the switch’s internal components are damaged or worn out.

If you notice any of these signs, it might be time to replace the ignition switch. Consult your owner’s manual or seek professional assistance to ensure you’re following the correct steps for your specific model.

Safety Switch Malfunctions

Safety switches are a crucial component of modern lawn mowers, including the John Deere series. These switches have been specifically designed to protect the operator and the mower from potential harm or damage.

Nonetheless, they can fail or become defective, preventing your mower from starting.

Faulty Seat Switch

To troubleshoot this problem, begin by examining the seat switch. This particular switch ensures the engine will only start when someone is properly seated on the mower.

If the seat switch is malfunctioning, it may prevent the engine from turning over even when you’re in the correct position. Test the seat switch for proper function and consider replacing it if necessary.

Bad Blade Engagement Switch

In addition to the seat switch, other safety switches on your John Deere lawn mower could be causing issues.

One of these is the blade engagement switch. This switch is responsible for activating and deactivating the cutting blades.

A faulty blade engagement switch might send mixed signals to the engine, preventing it from starting even when the blades are disengaged. Again, inspect this switch for any signs of wear or damage and replace it if needed.

Damaged Parking Brake Switch

Lastly, take a look at the parking brake switch. This safety mechanism ensures your mower won’t start unless the parking brake is engaged, avoiding any unintentional movement during startup.

If the parking brake switch is malfunctioning or damaged, it could hinder your mower’s ability to start even if everything else is in working order. Check this switch thoroughly and replace it if required.

Clogged Air Filter

As essential as oxygen is for humans, it is equally vital in keeping your mower’s engine alive and kicking. And just like we struggle when there’s no fresh air to breathe, your John Deere will gasp for life if its air filter is clogged with dirt or dust.

So how does a clogged air filter manage to bring your mower to its knees?

It’s simple, really. The air filter works like a guardian angel for your engine, filtering out impurities from the air before they can enter the combustion chamber.

When the filter becomes clogged, it severely restricts the airflow, causing the engine to work harder and consume more fuel. Eventually, this lack of oxygen can lead to a weakened performance or prevent your mower from starting altogether.

But fear not! Restoring that vibrant vigor to your verdant warrior is often a quick fix.

Simply remove the air filter, give it a thorough inspection, and clean it. If it’s beyond salvation, replace it, and watch as your John Deere springs back to life with renewed enthusiasm.

Experts recommend checking your air filter every 25 hours of use or at least once per mowing season. By keeping that breath of fresh air flowing through your John Deere’s lungs, you’ll ensure it remains ready for action whenever your lawn demands attention.

The Bottom Line

A John Deere lawn mower that won’t start can be frustrating. Yet, with a bit of patience and some detective work, you’ll likely find the problem at hand.

Before diving headfirst into an investigation of your lawn mower’s internal workings, it’s essential to exercise caution. Always consult your owner’s manual for guidance on proper troubleshooting techniques, as this will provide invaluable insight into the unique specifications of your particular model.

Equipped with this knowledge and a healthy dose of common sense, you can approach the task at hand confidently and safely. By being proactive and exploring these potential issues before seeking professional help, you might just save yourself time and money.

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