Solving No-Crank Issues in the Volvo EC120E Excavator

[MikePhua]

The EC120E and Volvo’s Excavator Lineage
Volvo Construction Equipment, a division of the Swedish industrial giant Volvo Group, has built a reputation for durable, operator-friendly machines with advanced hydraulic systems and efficient engines. The EC120E is part of Volvo’s compact-to-mid-size excavator range, designed for urban infrastructure, utility trenching, and light demolition. With an operating weight around 12 metric tons and a Volvo D4J Tier 4 Final engine producing roughly 100 horsepower, the EC120E balances power, fuel economy, and maneuverability.
Volvo’s excavator sales have grown steadily across North America, Europe, and Asia, with the EC120E gaining traction in markets that demand reliability and low emissions. However, like any electronically controlled machine, it can experience startup issues—particularly no-crank conditions that leave operators stranded and projects delayed.
Terminology Notes

• No-Crank Condition: When the starter motor does not engage or rotate the engine upon key activation.
  
• CAN Bus: A communication protocol used to link electronic control units (ECUs) across the machine.
  
• Starter Relay: An electrical switch that sends power to the starter motor when the ignition is engaged.
  
• Neutral Safety Switch: A sensor that prevents starting unless the machine is in a safe gear or position.
  

Common Causes of No-Crank Behavior
When an EC120E fails to crank, the issue typically falls into one of several categories:

• Electrical faults in the starter circuit
  
• Safety interlock failures
  
• Battery or cable degradation
  
• Faulty ignition switch or ECM logic
  
• CAN Bus communication errors
  

A contractor in British Columbia reported that his EC120E wouldn’t crank after a weekend shutdown. After checking the battery and fuses, he discovered the travel lock lever was slightly out of position, triggering the safety interlock and preventing starter engagement.
Electrical System Diagnostics
Start with the basics:

• Verify battery voltage under load; should exceed 11.5V during cranking
  
• Inspect battery terminals and ground straps for corrosion or looseness
  
• Test starter relay and solenoid for continuity and voltage drop
  
• Check ignition switch output to starter circuit
  
• Confirm voltage at starter motor during key-on
  

A technician in Texas traced a no-crank issue to a corroded ground strap between the frame and engine block. Replacing the strap restored full starter function.
Safety Interlocks and ECM Logic
Volvo machines use multiple safety inputs to prevent unintended starts:

• Neutral safety switch on travel controls
  
• Hydraulic lockout lever position sensor
  
• Seat switch and door sensor (on newer models)
  
• ECM logic requiring all conditions to be met before starter activation
  

If any of these inputs are misaligned, damaged, or misread, the ECM will block starter engagement. A fleet manager in Wisconsin found that a faulty hydraulic lockout sensor was intermittently preventing cranking. Replacing the sensor resolved the issue permanently.
Starter Motor and Solenoid Checks
Starter motors can fail gradually or suddenly:

• Listen for clicking without cranking—may indicate solenoid failure
  
• Inspect starter gear engagement and flywheel teeth
  
• Test amperage draw during cranking; excessive draw may indicate internal short
  
• Clean starter terminals and ensure solid ground
  

A municipal crew in Maine replaced the starter on their EC120E after noticing intermittent engagement. The new unit cranked faster and eliminated startup delays.
CAN Bus and Diagnostic Codes
Modern Volvo excavators rely on CAN Bus communication between ECUs. If a module fails or loses connection:

• The starter command may not reach the engine ECU
  
• Fault codes may be stored but not displayed without diagnostic software
  
• A failed display unit or fuse can block startup logic
  

A technician in Alberta used a laptop diagnostic tool to discover a lost connection between the cab controller and engine ECU. Re-seating the connectors and clearing the codes restored normal startup.
Preventive Measures and Operator Tips
To avoid future no-crank scenarios:

• Replace batteries every 3–5 years and test monthly
  
• Keep terminals clean and tight
  
• Inspect wiring harnesses for abrasion and corrosion
  
• Check safety switch alignment during service
  
• Perform periodic ECM scans to catch latent faults
  

A contractor in Oregon added a battery disconnect switch and surge protector to his EC120E. The upgrades prevented parasitic drain and protected the ECM during welding operations.
Anecdote from the Field
In 2023, a small excavation firm in Georgia had an EC120E that wouldn’t crank after a rainstorm. The operator suspected a dead battery, but a mechanic discovered water intrusion in the fuse box. A corroded fuse socket was preventing current flow to the starter relay. After cleaning the socket and replacing the fuse, the machine started immediately. The owner later installed a weatherproof cover to prevent recurrence.
Conclusion
No-crank conditions in the Volvo EC120E are often caused by overlooked electrical faults, safety interlock misalignment, or ECM logic errors. With a methodical diagnostic approach and basic tools, most problems can be resolved quickly. The EC120E may be compact, but its systems are sophisticated—and keeping it running means understanding both the hardware and the logic behind the start button.