John Deere 120C No Crank Problem: Troubleshooting and Solutions

[MikePhua]

The John Deere 120C is a popular compact excavator widely used in construction and excavation tasks. Like any heavy equipment, the 120C can experience issues that may prevent it from starting, with one common problem being the "no crank" issue. This problem can stem from several sources, including electrical, mechanical, or fuel-related issues. In this article, we will discuss the possible causes of the no crank issue on the John Deere 120C, along with troubleshooting steps and solutions.
Common Causes of No Crank Issue

1. Battery and Electrical Issues
   One of the most common reasons for a no crank problem in any piece of equipment, including the John Deere 120C, is a dead or weak battery. If the battery does not have enough charge, the starter motor will not receive sufficient power to crank the engine.
   • Symptoms: No sound from the starter motor, dim or non-functional lights, or sluggish operation of other electrical systems.
     
   • Solution: Check the battery charge level and connections. If the battery is old or unable to hold a charge, it may need to be replaced. Clean the battery terminals and check for corrosion, which can interfere with the electrical connections.
     
2. Starter Motor or Solenoid Failure
   The starter motor is a critical component that initiates the cranking of the engine. If the starter motor or solenoid (the component that activates the starter) fails, the engine will not crank. This issue can sometimes be identified by hearing a clicking sound when turning the key.
   • Symptoms: A single click or repeated clicking sound when attempting to start the machine, but the engine does not crank.
     
   • Solution: Test the starter motor by applying direct current (DC) power to it, bypassing the solenoid. If the motor operates, the solenoid or wiring might be the issue. If the motor does not work, the starter motor may need to be replaced.
     
3. Ignition Switch or Relay Malfunction
   The ignition switch is responsible for sending the signal to the starter to begin cranking. A faulty ignition switch or relay can prevent the signal from reaching the starter, causing the engine not to crank.
   • Symptoms: No electrical response when turning the key or a failure to engage the starter motor.
     
   • Solution: Test the ignition switch and relay using a multimeter to ensure they are functioning properly. If they are faulty, replace them with new, compatible parts.
     
4. Safety Switches and Interlocks
   Many modern machines, including the John Deere 120C, have safety switches and interlocks that prevent the engine from cranking under unsafe conditions. These switches include items such as seat switches, neutral position switches, and brake switches. If any of these switches are faulty or out of alignment, the engine will not start.
   • Symptoms: The machine will not crank, but there are no obvious issues with the battery or starter.
     
   • Solution: Check the seat switch, neutral switch, and brake switch. Ensure they are functioning correctly and in the proper position. If any of these components are defective, replace them or realign them as necessary.
     
5. Fuel System Problems
   While fuel system issues typically result in the engine cranking but not starting, a fuel system blockage or malfunction can sometimes prevent the engine from cranking altogether. This issue may be more common in machines that have been idle for an extended period.
   • Symptoms: The machine attempts to start, but there is no power or response from the engine.
     
   • Solution: Inspect the fuel lines, filter, and fuel pump for any blockages or malfunctions. Ensure the fuel is reaching the engine and that there is no air trapped in the fuel system.
     

Troubleshooting Steps

1. Inspect the Battery
   • Check the voltage of the battery using a multimeter. If the battery voltage is below 12 volts, recharge or replace the battery.
     
   • Inspect battery connections for corrosion and ensure they are tightly secured.
     
2. Test the Starter Motor and Solenoid
   • Use a multimeter or jumper cables to test the starter motor and solenoid.
     
   • If the solenoid clicks but the starter does not turn over, the starter motor may be faulty and require replacement.
     
3. Check the Ignition Switch and Relay
   • Test the ignition switch and relay using a multimeter to confirm they are sending power to the starter.
     
   • If they are not functioning, replace the defective components.
     
4. Examine the Safety Interlocks
   • Verify that all safety switches, including the seat, neutral, and brake switches, are functioning properly.
     
   • Ensure the machine is in neutral and the parking brake is engaged before attempting to start.
     
5. Inspect the Fuel System
   • Check the fuel filter and lines for any blockages or leaks.
     
   • Ensure that fuel is reaching the engine and that there is no air in the system.
     

Additional Tips and Solutions

• Electrical Connections: Loose or damaged wiring can also be a culprit in no-crank situations. Inspect all electrical connections and wires for wear or disconnections, especially around the battery, starter motor, and ignition system.
  
• Cranking Voltage: If the battery is fully charged and the starter still won’t engage, measure the cranking voltage. If the voltage drops significantly during starting attempts, it may indicate a problem with the wiring or a weak starter.
  
• Check for Fault Codes: If your John Deere 120C has diagnostic capabilities, check for any fault codes that could indicate an issue with the engine management system, safety switches, or other electrical components.
  

Conclusion
The John Deere 120C no crank issue can stem from various causes, including battery problems, starter motor failure, faulty relays, or issues with safety interlocks. By methodically diagnosing the problem using the troubleshooting steps outlined above, you can efficiently pinpoint the source of the issue and restore functionality to your excavator. Regular maintenance and timely repairs are essential to ensuring that your machine operates smoothly and reliably for many years to come.