Few things are more frustrating than climbing onto your John Deere lawn mower—known for its reliability and power—only to turn the key and get nothing. Whether you have a John Deere riding mower, zero-turn, or walk-behind, a no-start problem is common, especially after storage or heavy use. Luckily, most starting issues are simple to diagnose and repair at home. This in-depth guide will walk you through every step to get your John Deere mower running strong again.
Quick Picks: Most Common Reasons a John Deere Mower Won’t Start
- Dead or Weak Battery: The battery may be old, discharged, or have corroded connections.
- Bad or Stale Gasoline: Old fuel gums up the carburetor and fuel lines.
- Faulty or Dirty Spark Plug: The plug may be fouled, damaged, or not gapped properly.
- Clogged Fuel Filter or Lines: Fuel can’t reach the engine if filters or lines are blocked.
- Dirty Carburetor: Fuel residue or varnish blocks the jets inside the carburetor.
- Safety Switch Not Engaged: John Deere mowers use seat, brake, and blade switches that must be properly set or the mower will not start.
- Blown Fuse: A blown fuse interrupts power to the ignition system.
- Faulty Starter Solenoid or Ignition Switch: These can fail over time and prevent cranking.
Buyer’s Guide: What You’ll Need to Diagnose and Fix
- Socket and wrench set: For battery and spark plug removal.
- New spark plug and air filter: Always use the correct type for your John Deere model.
- Fresh gasoline: Use only new, clean fuel.
- Battery charger or replacement battery: For weak or dead batteries.
- Carburetor cleaner spray: To clear out old fuel residue.
- Multimeter: For testing voltage, fuses, and switches.
- Replacement fuse: Check your manual for the correct type.
- Gloves and safety glasses: For protection during repairs.
Step-by-Step Guide: How to Fix a John Deere Mower That Won’t Start
1. Check the Battery and Connections
- Lift the seat or access panel to find the battery. Test with a multimeter: a good 12V battery should read at least 12.4 volts.
- If voltage is low, try recharging. If the battery will not hold a charge, replace it.
- Inspect battery terminals for corrosion or looseness. Clean and tighten as needed.
2. Inspect the Spark Plug
- Remove the plug using a socket. Check for fouling, cracks, or worn electrodes.
- Clean lightly with a wire brush or replace with a new, correctly gapped plug.
- Reinstall and ensure the spark plug wire is securely attached.
3. Use Fresh Fuel and Check the Fuel Filter
- Drain out old gasoline from the tank and carburetor bowl. Replace with fresh fuel.
- Inspect the fuel filter for clogs or dirt. Replace if dirty or damaged.
- Make sure the fuel shutoff valve (if equipped) is in the “on” position.
4. Clean the Carburetor
- Spray carburetor cleaner into the intake with the air filter off.
- For deeper cleaning, remove the carburetor bowl and spray jets and passages until clear.
- Reassemble and try starting the mower again.
5. Check Safety Switches and Controls
- Ensure you are sitting on the seat, the brake pedal is fully pressed, and the blades are disengaged. All safety switches must be properly set or the engine won’t crank.
- If a switch is loose, broken, or wires are disconnected, repair or replace as needed.
- Test each switch for continuity with a multimeter if you suspect a failure.
6. Inspect Fuses and the Ignition Circuit
- Locate the mower’s fuse (often near the battery or ignition switch). Replace if blown with the correct rated fuse.
- If the ignition switch or starter solenoid makes no sound or movement, use a multimeter to check for power at each step of the circuit.
- Replace faulty ignition switches or solenoids as needed.
Comparison Table: John Deere Mower Starting Problems & Solutions
| Problem | Solution | Difficulty | Parts Needed |
|---|---|---|---|
| Dead/Weak Battery | Charge or replace battery | Easy | Battery, charger |
| Bad Gasoline | Drain and refill tank | Easy | Fresh gasoline |
| Dirty/Faulty Spark Plug | Clean or replace plug | Easy | Spark plug |
| Clogged Fuel Filter | Replace filter | Easy | Fuel filter |
| Dirty Carburetor | Spray or rebuild carburetor | Medium | Carburetor cleaner, gaskets |
| Blown Fuse | Replace fuse | Easy | Correct fuse |
| Bad Safety Switch | Repair or replace switch | Easy | Switch |
| Faulty Ignition or Solenoid | Replace switch or solenoid | Medium | Ignition switch, solenoid |
Frequently Asked Questions
Why does my John Deere mower only click but not start?
This usually means the battery is too weak or there’s a poor connection. Check and charge the battery, then inspect and clean the terminals.
How do I know if my safety switch is bad?
If your mower won’t crank even when all controls are set correctly, use a multimeter to check continuity on each safety switch. Replace any that fail the test.
Should I clean or replace my carburetor?
Light varnish or gumming can be cleaned with spray. If the mower still won’t start, a deeper cleaning or rebuild may be needed.
How often should I replace the battery in my John Deere mower?
Most batteries last 2–4 years. Replace at the first sign of weak cranking or inability to hold a charge.
When should I call a professional?
If you’ve tried all basic steps—battery, spark, fuel, filters, switches—and your mower still won’t start, a small engine technician can help with more advanced repairs.
Conclusion
Your John Deere lawn mower is built to last, but like all machines, it needs regular care and the occasional fix. When your mower won’t start, work through the basics: battery, fuel, spark, air, and safety switches. Most no-start problems are minor and easy to solve with a little time and the right parts. Stay on top of maintenance and your John Deere will keep your yard looking its best for years to come!