John Deere makes a good zero-turn mower. It’s beneficial for larger lawns because it cuts down on the time needed when compared to other mower types.
Even though it is a good mower with a reputable engine manufacturer, you will still run into problems over the course of its life.
Keeping your John Deere clean, using the right fuel, and routinely performing maintenance will help reduce potential problems and extend the useful life of your zero-turn.
I have put together a list to help you troubleshoot and narrow down the cause of your mower problem. You will find handy charts along with links to articles that go into more detail.
Follow the safety precautions listed in your John Deere operator’s manual to minimize injury while performing repairs. Always park your mower on a flat-level surface, remove the ignition key, and remove the spark plug wires prior to performing repairs.
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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.
Won’t Start
A John Deere zero-turn won’t start when the engine doesn’t get the air, fuel, and spark required to form an explosion to start. The battery, starter solenoid, and switches can also fail and cause a starting problem.
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Reasons a John Deere Zero Turn Mower Won’t Start
| Potential Cause | Solution |
|---|---|
| Empty fuel tank | Fill with fresh fuel. |
| Old fuel | Empty the fuel tank. Fill with fresh fuel and an additive to clean the fuel system like Sea Foam. |
| Bad spark plug | Replace a dirty or damaged spark plug. |
| Plugged air filter | Clean a dirty air filter. Replace a very dirty or damaged filter. |
| Plugged fuel filter | Replace the fuel filter. |
| Clogged fuel line | Remove and clean a clogged fuel line. Replace the line if needed. |
| Bad fuel pump | Replace a bad fuel pump. |
| Dirty carburetor | Remove and clean the carburetor. Rebuild or replace if damaged. |
| Bad battery, loose cables, or corroded terminals | Charge a weak battery. Replace a bad battery that won’t hold a charge. Secure cables and remove corrosion from components. |
| Bad safety switch | Replace a bad safety switch. |
| Bad ignition switch | Replace a bad ignition switch. |
| Bad starter solenoid | Test and replace a bad starter solenoid. |
Starts then Dies
Many of the items that cause a zero-turn to not start are also reasons a mower will die after running. In addition to these items, you’ll also need to check for a plugged mower deck, bad ignition coil, and low or high engine oil level.
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Reasons a John Deere Zero Turn Starts Then Dies
| Potential Cause | Solution |
|---|---|
| Old fuel | Drain the fuel tank. Mix fresh fuel with a fuel additive to stabilize gas, reduce moisture and clean the fuel system. Add to the fuel tank. |
| Plugged air filter | Clean a dirty air filter. Install a new filter when it is very dirty or damaged. |
| Dirty cooling fins | Clean around the cooling fins and replace damaged fins. |
| Clogged fuel line | Remove a clogged fuel line and attempt to remove the clog. Install a new fuel line when you can’t remove the restriction. |
| Bad fuel pump | Replace a bad fuel pump. |
| Dirty carburetor | Remove and clean a dirty carburetor. Rebuild or replace the carburetor when it can’t be sufficiently cleaned or internal parts are damaged. |
| Bad fuel cap / fuel tank vent | Replace a fuel cap that no longer allows the fuel tank to vent through the cap. |
| Wrong engine oil level | Correct the engine oil level by adding or removing a little oil until it is at the level recommended by the engine manufacturer. Consult a mechanic when this doesn’t solve the problem. The John Deere may have extensive engine damage. |
| Plugged mower deck | Scrape the mower deck. Sharpen the mower blades. |
| Bad ignition coil | Replace an ignition coil that has a break in continuity. |
| Dirty spark plug | Install new spark plug(s) when they are dark in color, damaged, or worn. Clean them with a wire brush when they are in good condition and slightly dirty. |
Won’t Move Forward or Reverse
The hydrostatic transmission pumps fluid to move the wheels. The pressure is so great that you will not be able to free-roll the zero turn without bypassing the transmission.
Make sure the transmission levers are not bypassing the transmission. Check the belt, pulleys, and tensioners to make sure they are securely in place and not damaged. Ensure the oil is fresh and at the full level.
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John Deere Zero Turn Won’t Move Forward or Reverse
| Potential Cause | Solution |
|---|---|
| Transmission bypass levers in the wrong position | Place the transmission bypass levers in the operating position. You will find a lever near each drive wheel. |
| Drive pump belt is worn | Replace a worn belt and confirm it is sitting securely around the pulleys. |
| Bad tensioner pulley | Replace the tensioner pulley. Grease the tensioner arm. |
| Missing or damaged idler arm spring | Replace a broken or missing spring. |
| Low or old hydraulic oil | Change your hydraulic oil at regular intervals as recommended by John Deere. Check your hydraulic oil periodically to ensure your hydraulic fluid is full. (Note: some transmissions are unserviceable. Consult the John Deere dealer for help) |
Zero Turn Vibrates & Shakes
Even if you have a seat suspension system, you still bounce around when mowing the lawn. When you develop a vibration, the shaking and bouncing can get worse.
Check for worn engine mounting bolts or a bad clutch. Inspect all of the linkages and remove all debris from the mower. Items on the mower deck can fail or wear causing pulleys and blades to wobble and the deck belt to become loose.
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Reasons Your John Deere Mower is Vibrating
| Loose or missing engine mounting bolts | Secure the engine mount bolts. Replace any worn or missing bolts. |
| Failing clutch | Replace a bad electric clutch. Replace a worn clutch cable, lever, or bushings on a manual engagement clutch. |
| Unbalanced or damaged mower blades | Replaced damaged blades. Make sure they are correctly balanced. |
| Foreign material wrapped around the blade shaft | Remove foreign objects wrapped around the blade shaft. Inspect the spindle and housing for damage. |
| Bad spindle housing bearings | Check the spindle bearings and replace them when worn. |
| Bad deck belt | Replace a worn or loose deck belt. |
| Bad pulleys | Replace damaged pulleys or pulleys where you feel restriction when turning by hand or a wobble due to a bad bearing. |
| Debris lodged in the mower | Clean the mower checking all crevices for debris. |
Engine Overheats
Engine oil plays an important part in keeping the engine cool. Use an air-cooled engine oil of the right viscosity that is high in zinc. Keep the engine oil level full.
Check for items that can block airflow around the engine including the cooling fins, engine shroud, and engine guard.
Inspect the air filter, mower deck, and mower blade condition.
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Your John Deere Lawn Mower Engine Overheats
| Potential Cause | Solution |
|---|---|
| Wrong engine oil | Drain the engine oil and fill it with fresh oil. Use a 10W-30 oil in most conditions. You may have to use a different viscosity in very warm conditions. |
| Low engine oil level | Drain the fuel tank. Refill with a fresh gas with an additive to clean the fuel system and stabilize the fuel. |
| Plugged engine cooling fins | Remove the carburetor and clean it to remove deposits that m |
| MIssing engine guard | Replace a missing engine guard. Securely attach a loose guard. |
| Plugged air filter | Replace a dirty air filter. |
| Plugged mower deck | Scrape the mower deck to remove grass clippings and debris. |
| Dull mower blades | Sharpen dull mower blades. Replace worn blades. |
| Overworking the engine | Slow down the ground speed to match the mowing conditions. Avoid cutting wet grass. Double or triple-cut an overgrown lawn. |
Zero Turn is Smoking
A John Deere zero-turn smokes when the air filter is plugged, the engine oil is not correct, or a bad engine gasket has caused oil to seep onto a hot surface like the muffler.
When you can’t find the cause of the smoke, you may have internal engine issues like a worn piston ring or a burnt valve. In this case, I recommend having a small engine technician perform tests to determine the cause.
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Why Your John Deere Lawn Mower is Smoking
| Potential Cause | Solution |
|---|---|
| Plugged air filter | Replace a plugged air filter. |
| Too much engine oil | Remove a little engine oil from the crankcase until it is corrected. Check the condition of the air filter. |
| Low engine oil level | Have a small engine technician inspect the engine. You can correct the engine oil level, but chances are the engine is damaged if it began smoking due to low engine oil. |
| Bad engine gasket | Locate the bad engine gasket and repair it. |
| Internal problems: piston ring or valve train | If you continue to experience engine smoking, a small engine technician must perform testing to determine the cause of internal engine damage. |
Weak Hydrostatic Transmission
Hydrostatic transmissions on a John Deere zero-turn may experience a weak transmission when the hydraulic oil is old or the hydraulic tank is low on oil.
It can also feel weak when the drive belt or tensioner pulley is worn or broken.
| Potential Causes | Solutions |
|---|---|
| Bad drive belt | Replace a worn pump drive belt |
| Bad tensioner pulley | Replace a bad tensioner pulley. Grease the tensioner arm. |
| Low or old hydraulic oil | Change the hydraulic oil at regular intervals. Keep the hydraulic oil level at the full level. |
Won’t Drive Straight or Steer Correctly
When a zero turn doesn’t drive straight and pulls to one side, check the tire pressures and dampers. If these items are in good condition, you may just need to track the mower so each tire rotates at the same speed.
| Potential Cause | Solution |
|---|---|
| Incorrect tire pressure | Ensure the tires are filled to the manufacturer’s specifications. The tire pressures must be equal on each side of the zero-turn. |
| Bad dampers | Replace with new dampers. |
| Tracking adjustment needed | Adjust the speed adjustment bolt to change the rotation speed of the tire so each tire moves at the same speed. Refer to your owner’s manual. |
Running Rough and Sputters
When you find your John Deere zero-turn is running rough and bogs down, look for items that can restrict fuel flow or airflow or can cause an intermittent spark.
You’ll also need to look at items that can put extra load on the engine like a fast ground speed, plugged mower deck, and dull mower blades. Not having your throttle at its fastest speed can also cause the engine to run sluggishly when the blades are engaged.
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John Deere Mower is Running Rough or Sputtering
| Potential Cause | Solution |
|---|---|
| Old fuel | Drain old fuel. Refill with a gas and fuel stabilizer mixture. |
| Clogged fuel line | Remove a clogged fuel line and remove the clog using carburetor cleaner and compressed air. Install a new fuel line when the clog can’t be removed. |
| Plugged fuel filter | Replace the fuel filter. |
| Dirty carburetor | Remove the carburetor to clean it. Rebuild or replace it if needed. |
| Bad gas cap | Replace a gas cap that no longer allows the fuel tank to vent. |
| Dirty spark plug | Clean a dirty plug using a wire brush. Install a new one if it is very dark in color, worn, or damaged. |
| Fast ground speed | Slow down the ground speed to match the mowing conditions. Slow down when mowing tall, thick, or wet grass so the engine isn’t under too much load. |
| Low engine speed | Place the throttle lever in its highest position when engaging the mower blades. |
| Plugged mower deck | Scrape the mower deck to keep it clean. |
| Dull mower blades | Sharpen the mower blades. |
Mower Blades Won’t Engage
The mower blades won’t engage on a John Deere zero turn when the PTO switch is faulty, the battery is weak, a safety switch failed or the clutch is bad.
The blades won’t turn when the belt is worn or has fallen off the pulleys due to a stretched belt, bad pulley bearing, or worn tensioner parts.
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John Deere Mower Blades Won’t Engage or Turn On
| Potential Cause | Solution |
|---|---|
| Worn mower deck belt | Replace a belt that is worn, cracked, or has a shiny glazed appearance. |
| Belt falls off the pulleys | Replace worn or damaged deck parts including a worn idler arm, worn spring, or bad pulleys. Replace a stretch mower deck belt. |
| Bad PTO switch | Replace the PTO switch. |
| Bad clutch | Replace the clutch. On a manual engagement clutch, replace a worn clutch cable, lever, springs, and linkages. |
| Weak battery | Test the battery and place it on a charger if the reading is less than 12.7 volts for a 12-volt battery. Replace the battery when it won’t hold a charge. |
| Bad Safety switch | Replace the safety switch |
| Blown fuse | Replace the fuse with the same capacity fuse. |
Leaking Gas
It can be difficult to find where a John Deere is leaking gas especially if the gas has evaporated into the air and doesn’t leave any wet spots behind.
Common areas to check for a leak is the carburetor and dry cracked fuel lines. You may also develop fuel leaks from fuel components from plastic components that degrade or seals that dry out.
For More Information Check Out:
Reasons Your John Deere Lawn Mower is Leaking Gas
| Potential Cause | Solution |
|---|---|
| Bad carburetor bowl gasket | Replace the gasket located between the carburetor bowl and the carburetor. |
| Stuck carburetor float or float needle | Clean the carburetor and replace any damaged parts. |
| Cracked fuel line | Replace the fuel line. |
| Bad fuel tank | Replace a fuel tank that begins leaking at the seams |
| Bad fuel shut-off valve | Replace the fuel shut-off valve |
| Weak fuel filter | Install a new fuel filter. |
| Bad fuel pump | Install a new fuel pump. |
| Bad gas cap seal | Replace the gas cap. You may be able to purchase only the rubber seal on some caps. |
Clicks & Won’t Turn Over
When the John Deere zero-turn just clicks when you go to start it, you may have a bad starter solenoid. In addition to the solenoid, check the items that can affect the power getting to the solenoid.
These include the battery, cables, terminals, and ground. When the fault doesn’t lie with any of these items, check the starter motor.
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John Deere Lawn Mower Clicks But Won’t Turn Over
| Potential Cause | Solution |
|---|---|
| Damaged or loose battery cables & wiring | Replace damaged cables. Remove any corrosion on the terminals or other components. Secure loose cables. |
| Weak or bad battery | Test the battery and place it on a charger if the reading is less than 12.7 volts for a 12-volt battery. Replace the battery when it won’t hold a charge. |
| Bad ground | Remove corrosion from the ground. Make sure the ground cable from the battery and ground cable from the starter solenoid is making good contact. (A 3-post solenoid is self-grounded) |
| Faulty starter solenoid | Test the starter solenoid and replace it if faulty. |
| Bad starter motor | Replace a bad starter motor. |
Has a Bad or Uneven Cut
There are many items that can affect the cut quality of your John Deere zero-turn. First, check the tire pressures to make sure you don’t have a low tire that is causing the deck to sit unleveled.
Next, at the condition of the components on the top of your mower deck and underneath the deck. Sharpen dull blades, replace components with bad bearings and replace a worn deck belt.
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Reasons for a John Deere Zero Turn Bad or Uneven Cut
| Potential Cause | Solution |
|---|---|
| Dull or worn mower blades | Sharpen the mower blades. Replace blades that are extremely worn where the blade sails are thinner than the center of the blade or the blade ends are worn and rounding. |
| Bent mower blade | Replace a bent mower blade. |
| Blade installed wrong | Make sure the blades are installed with the correct hardware. The blade sails must be pointed upward toward the mower deck. |
| Bent blade spindle | Replace a bent spindle. Inspect the spindle housing for damage. |
| Bad mower deck belt or bad pulleys | Replace a deck belt that is stretched, worn, cracked, or has a glazed appearance. Slowly rotate the pulleys by hand. Replace the pulleys when you feel a restriction, hear a bearing noise, or the pulley is wobbling. |
| Mower deck is plugged with grass clippings & debris | Scrape the mower deck. |
| Uneven tire pressure | Correct the tire pressures. Make sure they are even on the left and right-hand sides. |
| Unleveled mower deck | Level the mower deck so the mower deck is level side-to-side. The mower deck sits slightly lower in the front than in the rear. Consult the operator’s manual for exact specifications to level the deck. |
| Engine speed is too low | When engaging the blades, have the throttle set at the highest level. |
| Ground speed is too fast | Slow down when mowing thick, wet or tall grass. Mowing in these conditions puts extra strain on the engine. Running the mower too fast can end up pushing over some grass instead of cutting it. |
| Operator error | Properly overlap paths so strips of grass are not left in between passes. Use a small format deck like a push mower to mow ditches and other steep changes in grade. |