Solving Intermittent Stalling Issues on the Volvo L90 Loader

[MikePhua]

The Volvo L90 Legacy and Global Footprint
The Volvo L90 wheel loader is part of Volvo Construction Equipment’s renowned L-series, which has been a staple in the earthmoving industry since the 1980s. Known for its balance of power, maneuverability, and operator comfort, the L90 has evolved through multiple generations—from the L90C to the L90F and beyond—each iteration incorporating tighter emissions standards, improved hydraulic response, and smarter electronic controls.
Volvo CE, headquartered in Eskilstuna, Sweden, has produced over 100,000 units of the L90 series globally. The L90 is especially popular in Europe, Australia, and North America, where it’s used in quarrying, road maintenance, and municipal work. Its reputation for reliability is well-earned, but like any machine, it’s not immune to age-related quirks—one of the most frustrating being random engine stalls.
Symptoms of the Intermittent Stall
Operators have reported that the L90 engine will suddenly shut off without warning. This can happen while idling, shifting gears, or even while traveling across uneven terrain. Restarting the machine typically requires shifting into neutral, cycling the ignition, and waiting for two or three crank attempts before the engine fires again.
Key symptoms include:

• No fault codes displayed on the dash
  
• Stalls occur both stationary and in motion
  
• Restart is possible but inconsistent
  
• Fuel filters and electrical connectors appear clean
  

This type of failure is particularly disruptive in production environments, where downtime translates directly into lost revenue and frustrated crews.
Stop Solenoid Vulnerability and Heat Exposure
One of the most common culprits in older L90 models is the stop solenoid—a DC-powered actuator responsible for cutting fuel flow when the ignition is turned off. On earlier units, this solenoid is mounted close to the engine block, exposing it to high temperatures and vibration. Over time, the solenoid may fail to hold its position, causing the engine to shut down unexpectedly.
Technicians have found that relocating the solenoid using an extension bracket and heat-shielded wiring can dramatically improve reliability. This retrofit kit is available from aftermarket suppliers and includes:

• A vibration-dampened mounting bracket
  
• Heat-resistant wiring harness
  
• Weather-sealed connectors
  

In one case from Norway, a fleet manager retrofitted five L90 loaders with this kit and reported a complete elimination of random stalls over a six-month period.
Charging System and Voltage Drop Issues
Another overlooked factor is the health of the charging system. The L90 relies on stable voltage to maintain electronic control unit (ECU) operations and solenoid actuation. If the alternator brushes are worn or the voltage regulator is erratic, the system may dip below the critical threshold, triggering a stall.
Recommended checks include:

• Measure voltage at idle and under load (should remain above 13.5V)
  
• Inspect alternator brushes for wear or carbon buildup
  
• Test battery condition and terminal integrity
  
• Check for corrosion in ground straps and chassis bonding points
  

A Canadian operator discovered that his L90’s stalling issue was resolved after replacing a failing alternator that intermittently dropped voltage below 12V during gear shifts.
Fuel Delivery and Suction Line Diagnostics
The L90’s fuel system includes a belt-driven lift pump and a primary suction line from the tank. If the suction line is partially blocked, cracked, or leaking air, fuel delivery may become erratic—especially under vibration or incline.
A practical diagnostic method involves bypassing the onboard tank:

• Disconnect the suction line and place it in a clean 5-gallon fuel container
  
• Run the loader under normal conditions
  
• Observe whether stalling persists
  

If the issue disappears, the problem likely lies in the tank pickup, internal screen, or suction hose integrity. In one Australian case, a loader was found to have a collapsed internal pickup tube that intermittently blocked fuel flow during movement.
Fuel Control Valve and Pressure Monitoring
Modern L90 models use a Fuel Control Valve (FCV) to regulate pressure and flow to the injectors. A failing FCV may not trigger fault codes but can cause pressure drops that lead to stalls. Some units may display a PSID 096-1 code, indicating fuel pressure irregularities.
To assess FCV performance:

• Use a diagnostic tool to monitor live fuel pressure
  
• Compare readings against manufacturer specs (typically 4–6 bar at idle)
  
• Inspect for leakage behind the pulley or shaft play in the lift pump
  
• Replace FCV if pressure fluctuates or drops below threshold
  

A technician in Scotland noted that replacing the FCV on a Tier III L90F resolved intermittent stalling that had persisted for weeks without any diagnostic codes.
Model-Specific Considerations and Emissions Tier Differences
The L90 has evolved through multiple emissions tiers:

• L90E: Tier II, mechanical injection, fewer sensors
  
• L90F: Tier III, electronic injection, more complex diagnostics
  
• L90G and later: Tier IV, SCR and DPF systems, CAN-based control
  

Understanding the model variant is crucial. Tier III and IV machines are more sensitive to voltage fluctuations and sensor anomalies, while Tier II units are more mechanical and forgiving. Always verify the model and emissions tier before beginning diagnostics.
Preventive Measures and Long-Term Solutions
To reduce the likelihood of intermittent stalls:

• Replace fuel filters every 500 hours
  
• Inspect and clean electrical connectors quarterly
  
• Monitor voltage and battery health monthly
  
• Retrofit heat shields and relocate vulnerable components
  
• Keep a log of fault codes and operating conditions during stalls
  

Fleet managers are encouraged to implement a proactive maintenance schedule that includes fuel pressure testing and alternator load checks. These steps can prevent costly downtime and extend the life of critical components.
Conclusion
Intermittent stalling in the Volvo L90 loader is a multifaceted issue that can stem from solenoid failure, voltage instability, fuel delivery problems, or control valve malfunction. By combining methodical diagnostics with practical field tests, operators can isolate the root cause and restore reliable performance. The L90 remains a workhorse in the industry, and with thoughtful maintenance, it continues to deliver productivity across continents and job sites.