When a Machine Clicks but Refuses to Start

[MikePhua]

The Common Scenario of Starter Failure
Heavy equipment left idle on a job site for weeks can develop electrical issues that prevent it from starting. One of the most frequent symptoms is a distinct click when the ignition key is turned, but no engine turnover. This issue typically points to a problem in the starting circuit—either electrical or mechanical—and is especially common in machines like the Volvo BL71 backhoe, which rely on robust but aging starter systems.
The click sound often comes from the starter solenoid engaging, but the motor itself fails to spin. This can be caused by low voltage, poor connections, a faulty relay, or a seized starter motor. Diagnosing the issue requires a methodical approach, especially when the machine has been exposed to moisture or corrosion.
Initial Checks Before Replacing Parts
Before assuming the starter motor is dead, several basic checks should be performed:

• Ensure the transmission is in neutral. Most machines have a neutral safety switch that prevents starting in gear.
  
• Inspect battery terminals and ground connections. Corrosion or loose clamps can cause voltage drop.
  
• Hold the key in the start position and feel for heat at the starter, solenoid, and cables. Warm spots indicate resistance or poor contact.
  
• Tap the starter housing with a screwdriver handle. This can temporarily free stuck brushes or contacts.
  

A technician in Wales once revived a non-starting loader by simply cleaning the battery tray and bypassing the battery disconnect switch. The machine roared to life, proving that sometimes the solution is simpler than expected.
Understanding the Starter Circuit
The starter system includes:

• Battery
  Supplies power to the entire circuit. Must be fully charged and capable of delivering high current.
  
• Starter Solenoid
  Acts as a relay, sending power to the starter motor when the key is turned.
  
• Starter Motor
  Spins the engine flywheel to initiate combustion.
  
• Neutral Safety Switch
  Prevents starting unless the transmission is in neutral.
  
• Battery Disconnect Switch
  Cuts power to prevent parasitic drain or unauthorized use.
  

If the solenoid clicks but the motor doesn’t turn, the issue may lie in:

• Insufficient voltage reaching the starter
  
• Internal failure of the starter motor
  
• Faulty solenoid contacts
  
• High resistance in cables or terminals
  

Jumping the Solenoid Safely
To test the starter directly:

• Ensure the machine is in neutral and parking brake is engaged.
  
• Use a heavy wire to jump between the large terminals on the solenoid.
  
• Alternatively, use a small wire to jump from the battery terminal to the solenoid’s signal terminal.
  

If the starter engages, the issue is upstream—likely in the ignition switch, relay, or wiring. If it doesn’t, the starter or solenoid may need replacement.
A mechanic in North Carolina recommends leaving the key off during jumping to avoid accidental engine start. He uses a test light and voltmeter to trace voltage through the circuit, checking each terminal for proper response when the key is turned.
Moisture and Engine Seizure Risks
If the starter hums but doesn’t turn, or if all connections heat up evenly, the engine itself may be seized. Water ingress through the exhaust or air intake can cause internal rust and hydraulic lock.
To check:

• Attempt to rotate the engine manually by pulling on the fan belt or using a crank tool.
  
• Remove injectors or glow plugs to relieve pressure if water is suspected.
  
• Inspect oil and coolant for signs of contamination.
  

A backhoe left in heavy rain for weeks may develop internal condensation, especially if the exhaust was uncovered. Preventive measures include sealing the intake and exhaust and using desiccant packs in the cab.
Battery Disconnect Switches and Their Role
Battery disconnect switches are useful for isolating power during storage or transport. However, they can corrode internally or fail mechanically, cutting off power even when switched on.
Replacing a faulty disconnect switch is recommended if:

• Bypassing it restores function
  
• Voltage is present at the battery but not at the starter
  
• The switch feels loose or fails to click firmly
  

A new switch typically costs $20–$60 and can prevent future no-start scenarios.
Conclusion
When a machine clicks but won’t start, the cause is often electrical and easily diagnosed with basic tools. From corroded terminals to faulty solenoids and disconnect switches, the starting circuit offers multiple points of failure—but also multiple opportunities for quick fixes. With a structured approach and attention to safety, operators can restore function without costly downtime. In the world of heavy equipment, even a stubborn click can be the start of a simple solution.