Volvo L120E with D7D Engine Not Starting: Troubleshooting and Solutions

[MikePhua]

The Volvo L120E, equipped with the D7D engine, is a reliable and powerful wheel loader known for its versatility in construction, mining, and material handling. However, like any complex machine, it can experience operational issues, with one of the more frustrating problems being a failure to start. This issue can be caused by several factors, from electrical malfunctions to fuel system failures, and diagnosing the root cause is crucial for timely repairs.
Understanding the Volvo L120E and D7D Engine
The Volvo L120E is part of Volvo’s L-series of wheel loaders, which are widely regarded for their durability, performance, and fuel efficiency. Powered by the D7D engine, a turbocharged 6-cylinder diesel engine, the L120E delivers up to 175 horsepower, making it suitable for heavy-duty applications.
The D7D engine itself is known for its robust performance but, like any engine, it requires proper maintenance and attention to potential issues like fuel delivery, electrical systems, and starting mechanisms.
Common Causes of Starting Failures
When a Volvo L120E with a D7D engine fails to start, the issue is often related to one of several common culprits. These can include:
1. Battery or Electrical System Problems

• Battery Charge: A dead or weak battery is one of the most common reasons for a failure to start. Over time, batteries lose charge, especially if the machine is not used regularly. It’s important to check the battery voltage using a multimeter to ensure it meets the required specifications.
  
• Battery Terminals: Corroded or loose battery terminals can cause poor electrical contact, preventing the starter motor from receiving the necessary power to turn over the engine.
  
• Starter Motor: If the starter motor is malfunctioning or worn out, it will fail to engage the engine, preventing it from starting. Listening for a clicking noise when trying to start can help identify this issue.
  
• Fuses and Relays: Sometimes, an electrical fuse or relay related to the starting circuit may blow, causing a lack of power to the starter motor or ignition system.
  

2. Fuel System Issues

• Fuel Contamination: Water or debris in the fuel can clog the filters or injectors, preventing the engine from starting. Inspecting the fuel system for signs of contamination is an essential step.
  
• Fuel Pump Failure: If the fuel pump is not supplying fuel at the correct pressure, the engine will not start. This can be a result of wear, damage, or a malfunctioning component.
  
• Air in the Fuel Lines: Air trapped in the fuel system can prevent the engine from receiving the necessary fuel supply, making it impossible to start. Bleeding the fuel system to remove air is an essential step in addressing this issue.
  
• Clogged Fuel Filters: Over time, fuel filters can become clogged with dirt, rust, and other debris, restricting the flow of fuel. Replacing clogged filters can resolve starting issues.
  

3. Ignition and Sensor Malfunctions

• Faulty Sensors: Modern diesel engines like the D7D rely on several sensors to monitor key parameters such as temperature, pressure, and airflow. A malfunctioning sensor can send incorrect signals to the engine control unit (ECU), preventing the engine from starting. Common sensors to check include the crankshaft position sensor and camshaft position sensor.
  
• Glow Plugs: In colder weather, faulty glow plugs can prevent the engine from starting by failing to properly preheat the combustion chamber. Testing the glow plugs for proper function can help determine if they are the issue.
  

4. Starter Circuit Issues

• Neutral Safety Switch: Some machines, including the Volvo L120E, are equipped with a neutral safety switch that prevents the engine from starting unless the transmission is in neutral or park. If this switch malfunctions, it can prevent the engine from starting.
  
• Solenoid Issues: The solenoid is responsible for engaging the starter motor when the ignition is turned. A faulty solenoid can fail to send the correct signal to engage the starter, causing a no-start condition.
  

Troubleshooting Steps for the Volvo L120E D7D Engine
To effectively diagnose and address the issue of the Volvo L120E with the D7D engine not starting, follow these troubleshooting steps:
1. Check the Battery and Electrical System

• Measure Voltage: Use a multimeter to check the voltage across the battery terminals. If it’s below 12 volts, recharge or replace the battery as needed.
  
• Inspect the Battery Terminals: Clean the terminals and ensure they are tightly connected. Look for signs of corrosion, which can impede electrical flow.
  
• Check the Fuses and Relays: Examine the fuse box and relays associated with the starter circuit. Replace any blown fuses or faulty relays.
  

2. Inspect the Fuel System

• Examine Fuel Quality: Inspect the fuel tank for any signs of water or contamination. If necessary, drain the fuel and replace it with clean diesel.
  
• Check the Fuel Filters: Inspect the fuel filters for clogging and replace them if needed.
  
• Test the Fuel Pump: Ensure the fuel pump is delivering fuel at the correct pressure. If there is an issue with the pump, it may need to be repaired or replaced.
  
• Bleed the Fuel System: If air is trapped in the fuel lines, use the appropriate procedures to bleed the system and restore proper fuel flow.
  

3. Inspect the Ignition and Sensors

• Test the Glow Plugs: Check the glow plugs for proper function, especially in colder weather. If necessary, replace any faulty glow plugs.
  
• Check Sensor Connections: Inspect all relevant sensors for proper connections and functionality, especially the crankshaft and camshaft position sensors.
  

4. Examine the Starter Circuit

• Test the Starter Motor and Solenoid: Listen for a clicking noise when attempting to start the engine. If there is no sound, the starter motor or solenoid may need replacement.
  
• Inspect the Neutral Safety Switch: Ensure that the neutral safety switch is functioning correctly, allowing the engine to start only when the transmission is in the proper position.
  

Conclusion
The issue of a Volvo L120E with a D7D engine not starting can arise from various causes, including electrical problems, fuel system malfunctions, ignition issues, or starter circuit failures. By following a systematic troubleshooting approach, operators can isolate the root cause and take the necessary steps to resolve the issue. Regular maintenance and attention to the key components, such as the battery, fuel system, and sensors, can help prevent future starting problems and ensure the reliable performance of the L120E loader.
For operators facing persistent starting problems, it’s always advisable to consult with a certified mechanic or Volvo service provider to ensure that the issue is properly addressed and that the equipment is restored to peak operational performance.