How to Diagnose and Fix a New Injector Pump That Won't Send Fuel to Injectors on a Komatsu 287B Loader

[MikePhua]

An injector pump that fails to send fuel to the injectors can cause a diesel engine to refuse to start or run poorly. This problem can occur even with a new injector pump installed, such as on a Komatsu 287B multi-terrain loader, causing significant frustration for operators and technicians alike. This detailed guide explains possible causes, diagnostic steps, and practical solutions for this issue, along with relevant terminology and maintenance tips to ensure reliable fuel injection.

Understanding the Injector Pump and Its Role
The injector pump is a critical component that pressurizes and delivers diesel fuel to each cylinder’s injector at the precise timing and amount needed for combustion. On a Komatsu 287B:

• Injector Pump: Mechanically or electronically driven device supplying fuel at high pressure to each injector.
  
• Solenoid: An electrically controlled valve in the pump regulating fuel flow or enabling fuel delivery.
  
• Fuel Injectors: Components that spray fuel into engine cylinders.
  
• Fuel Lines and Filters: Deliver clean fuel from the tank to the pump and injectors.
  
• Ground Strap: Electrical grounding ensuring proper function of solenoids and sensors.
  

If the pump does not send fuel, the engine will not fire or start.

Common Causes of a New Injector Pump Not Sending Fuel

• Electrical Problems:
  • Faulty or damaged solenoid on the injector pump.
    
  • Wiring harness issues such as broken wires, poor connectors, or shorts.
    
  • Missing or faulty ground strap affecting solenoid or pump operation.
    
• Fuel Supply Issues:
  • Air trapped in the fuel system causing airlocks.
    
  • Blocked or dirty fuel filters restricting flow.
    
  • Improper bleeding or priming of the fuel system after pump installation.
    
• Mechanical Faults:
  • Defective pump pressure regulator or internal pump failure, even if new.
    
  • Incorrect installation or damaged internal parts during replacement.
    
• Control System and Sensors:
  • Faulty engine control components that inhibit pump activation.
    

Step-by-Step Diagnostic and Troubleshooting Guide

1. Check Electrical Connections
   • Inspect the solenoid wiring harness for continuity, damage, or corrosion.
     
   • Verify the solenoid receives proper voltage when the key is turned.
     
   • Confirm the ground strap near the fuel tank or pump is intact and well-attached.
     
2. Test the Solenoid
   • Use a multimeter to measure solenoid coil resistance; compare with specifications.
     
   • Apply direct power to the solenoid to confirm it actuates.
     
3. Inspect Fuel Supply
   • Check fuel filter cleanliness; replace or clean if clogged.
     
   • Examine fuel lines for leaks, kinks, or blockages.
     
   • Prime the fuel system thoroughly to remove trapped air using manual priming pump or vacuum bleeder.
     
4. Prime the Fuel System
   • Open injector lines or bleeder nipples to bleed air until fuel flows freely.
     
   • Use a vacuum pump to assist bleeding if necessary.
     
   • Pump the manual priming lever multiple times to build pressure.
     
5. Check Pump Installation
   • Confirm that the pump timing and alignment are correct per the Komatsu service manual.
     
   • Inspect for damage to internal components if the pump was rebuilt or remanufactured.
     
6. Examine Control Inputs
   • Verify any control modules or sensors linked to the pump operation.
     
   • Check engine control unit (ECU) or ignition system if applicable.
     
7. Mechanical Testing
   • If electrical and fuel supply checks pass but fuel still does not flow, the pump may internally malfunction.
     
   • Disassemble or return the pump for inspection or rebuild as necessary.
     

Practical Case Example
A Komatsu 287B owner replaced their injector pump with a brand-new unit but experienced no fuel delivery to the injectors. Upon closer inspection, it was found that the solenoid was not receiving power due to a broken wiring harness and a missing ground strap behind the fuel tank. Repairing the wiring and reinstalling the ground strap allowed the solenoid to energize properly, restoring fuel flow and engine starting capability. The fuel system was also bled carefully to eliminate airlocks, ensuring consistent operation.

Maintenance and Prevention Tips

• Always check electrical grounds and wiring thoroughly during pump replacement.
  
• Use quality OEM or certified components to avoid premature failure.
  
• Carefully bleed the fuel system to prevent air pockets.
  
• Regularly inspect fuel filters and replace on schedule to ensure flow.
  
• Follow manufacturer guidelines for injector pump installation, alignment, and timing.
  
• Ensure all sensor and control systems are functioning and communicating correctly.
  
• Maintain clean fuel and tank to minimize contamination risks.
  

Key Terminology

• Solenoid: Electromagnetic actuator controlling fuel flow within the pump.
  
• Ground Strap: Electrical conductor ensuring effective grounding for circuits.
  
• Priming: The process of removing air from the fuel system to allow proper fuel flow.
  
• Airlock: A pocket of air trapped inside the fuel line causing interruption of flow.
  
• Fuel Injector: Device that sprays pressurized fuel into the engine cylinders.
  
• Wiring Harness: Bundle of wires that carry electrical signals and power.
  
• Vacuum Bleeder: Tool to create vacuum pressure and assist bleeding air from the fuel system.
  

Summary List: Key Actions to Fix Injector Pump Fuel Delivery Issues

• Inspect and repair solenoid wiring and connectors.
  
• Confirm and reinstall proper grounding, including the ground strap.
  
• Replace clogged fuel filters and clean fuel lines.
  
• Bleed the fuel system manually or with a vacuum bleeder to remove airlocks.
  
• Test solenoid coil resistance and functioning.
  
• Check pump installation alignment and timing.
  
• Inspect engine control systems affecting pump activation.
  
• Consider pump mechanical integrity if all else fails.
  

Conclusion
A new injector pump that fails to deliver fuel can stem from a variety of electrical, mechanical, and fuel supply-related issues. Meticulous inspection of the solenoid and wiring, ensuring solid grounding, diligent bleeding of fuel lines, and verifying pump installation can restore fuel flow and engine operation. Real-world examples emphasize the importance of electrical integrity and bleeding procedures alongside mechanical checks.