Troubleshooting the JD650J: Why It Won't Start

[MikePhua]

The JD650J is a reliable crawler dozer from John Deere, commonly used in heavy construction and landscaping tasks. However, like any complex machinery, it can occasionally experience starting issues. When the JD650J won’t start, the problem could be due to various factors, ranging from fuel system issues to electrical or mechanical failures. This article provides a comprehensive guide on troubleshooting and resolving common starting problems in the JD650J.
Common Causes for JD650J Not Starting

1. Battery and Electrical System Issues
   • Symptoms: The engine cranks slowly or does not crank at all, and there may be no lights or power to the machine.
     
   • Possible Causes:
     • Weak or dead battery.
       
     • Loose or corroded battery terminals.
       
     • Faulty starter motor.
       
     • Blown fuses or electrical connections.
       
   • Solution:
     • Check the Battery: Start by testing the battery voltage. A battery with low voltage may need to be charged or replaced.
       
     • Clean and Tighten Connections: Inspect the battery terminals for corrosion or loose connections. Clean the terminals and ensure they are tightly connected.
       
     • Starter Motor Check: If the battery is fine, but the engine still doesn’t start, test the starter motor. A faulty starter motor may need to be replaced.
       
2. Fuel System Problems
   • Symptoms: The engine turns over but doesn’t start, or it may start briefly and then stall.
     
   • Possible Causes:
     • Empty fuel tank.
       
     • Clogged fuel filter.
       
     • Air in the fuel system.
       
     • Faulty fuel pump.
       
   • Solution:
     • Check Fuel Levels: Ensure there’s enough fuel in the tank. Even if it seems obvious, running out of fuel can often be overlooked.
       
     • Fuel Filter Inspection: Check the fuel filter for clogs. If the filter appears dirty or clogged, replace it with a new one.
       
     • Bleed the Fuel System: If air has entered the fuel lines, it can prevent the engine from starting. Bleed the fuel system to remove trapped air.
       
     • Fuel Pump Function: If the machine still won’t start after addressing the above, test the fuel pump to ensure it’s delivering the required fuel pressure. A malfunctioning pump may need replacement.
       
3. Ignition System Problems
   • Symptoms: The engine cranks but doesn’t fire, or there is no spark at the spark plug.
     
   • Possible Causes:
     • Faulty ignition switch.
       
     • Defective ignition coil or spark plug.
       
     • Malfunctioning engine control module (ECM).
       
   • Solution:
     • Ignition Switch Test: Check the ignition switch to ensure it’s functioning properly. A faulty ignition switch can prevent power from reaching the starter or ignition system.
       
     • Check Spark Plugs: Remove and inspect the spark plugs. If they are fouled, replace them. Also, check the ignition coil for signs of wear or damage and replace it if necessary.
       
     • ECM Check: If the ignition system components seem fine, the issue might lie with the engine control module (ECM). Have the ECM diagnosed using a diagnostic scanner to check for any fault codes.
       
4. Safety and Interlock System
   • Symptoms: The engine won’t start, but there are no obvious issues with the battery or fuel system.
     
   • Possible Causes:
     • Faulty safety interlock switches (seat, neutral, or park brake).
       
     • Transmission lever not in the correct position.
       
   • Solution:
     • Check Safety Interlocks: Many heavy equipment machines have safety features that prevent the engine from starting unless certain conditions are met, such as being in neutral, the park brake being engaged, or the operator being seated. Check all safety interlocks to ensure they are functioning properly.
       
     • Transmission and Gear Position: Verify that the transmission lever is in the correct position for starting (typically neutral). If the lever is out of position, it can prevent the engine from starting.
       
5. Engine Mechanical Issues
   • Symptoms: The engine turns over but doesn’t start, or it starts intermittently and then stalls.
     
   • Possible Causes:
     • Lack of compression.
       
     • Timing issues.
       
     • Valve or piston problems.
       
   • Solution:
     • Compression Test: Perform a compression test to check if the engine has adequate compression. Low compression could be caused by worn piston rings, valves, or gaskets.
       
     • Timing Check: Inspect the engine’s timing. A timing issue can cause the engine to misfire or not start at all. If the timing is off, it may require professional adjustment.
       

General Troubleshooting Steps

1. Step 1: Inspect the Battery and Electrical System
   • Check the battery voltage, clean the terminals, and ensure all connections are tight. Test the starter motor and ensure no blown fuses are preventing the system from receiving power.
     
2. Step 2: Examine the Fuel System
   • Ensure the fuel tank has sufficient fuel, and inspect the fuel filter for blockages. Bleed the fuel system to remove air, and check the fuel pump’s operation.
     
3. Step 3: Test the Ignition System
   • Check the spark plugs and ignition coil for proper function. Test the ignition switch and ECM for faults.
     
4. Step 4: Verify Safety Interlocks
   • Ensure that the safety interlocks are functioning and that the machine is in the correct starting position.
     
5. Step 5: Check for Mechanical Issues
   • Perform a compression test and inspect the engine’s timing and internal components for potential mechanical failures.
     

Conclusion
When the JD650J won’t start, it can be frustrating, but by following a methodical troubleshooting process, you can identify the root cause and resolve the issue. Begin by checking the battery, fuel system, and ignition system, as these are the most common sources of problems. Always ensure the safety interlocks and transmission are in the correct position, and be prepared to check for mechanical issues if the simpler solutions don’t work. By addressing these potential issues, you can get your JD650J back up and running efficiently.