2011-2016 LML 6.6 Duramax Cp4 injectors fuel rails and line replacement

Introduction

This tutorial provides a step-by-step guide for replacing the CP4 pump, injectors, fuel rails, and lines on a 2011-2016 LML 6.6 Duramax engine. Whether you're a seasoned mechanic or a DIY enthusiast, this guide aims to simplify the process, ensuring you have all the essential steps and tips for a successful replacement.

Step 1: Prepare the Vehicle

• Disconnect the battery on both sides to ensure safety.
• Remove the inner fender well for better access to components.
• Drain the coolant to prevent spills when working with the EGR cooler and crossover.

Step 2: Remove the Fuel Filter and Housing

• Unplug the water-in-fuel sensor and disconnect the fuel lines from the filter housing.
• Remove the bracket bolts to tilt the filter housing for easier access to the lower bolts.
• Completely remove the fuel filter housing from the vehicle.

Step 3: Disconnect Electrical Connections

• Disconnect the wiring harness connected to the injectors and glow plugs.
• Ensure all connectors are labeled for easy reassembly later.

Step 4: Remove Injector Lines and Hold Downs

• Use a crow's foot wrench to loosen the injector lines at the rail and injectors.
• Remove the injector hold downs carefully to avoid damaging any components.

Step 5: Extract the Old Injectors

• Gently pry out the injectors using a suitable tool. If stuck, flip the injector upside down and tap it lightly.
• Keep track of the order of the injectors for reinstallation.

Step 6: Install New Injectors

• Lubricate the O-rings of the new injectors with clean engine oil.
• Insert the injectors into their respective positions and secure them with hold downs.
• Torque the injector bolts to 22 foot-pounds.

Step 7: Install New Fuel Rails and Lines

• Position the new fuel rails and connect the injector lines according to their labels.
• Ensure all connections are tight and secure to prevent leaks.

Step 8: Replace the CP4 Pump

• Disconnect the necessary lines and electrical connections from the old CP4 pump.
• Remove any brackets or components blocking access to the pump.
• Install the new CP4 pump, ensuring all connections are properly seated.

Step 9: Reassemble Components

• Reattach the fuel filter housing and any removed brackets.
• Reconnect all electrical connections to the injectors and sensors.
• Reinstall the inner fender well and any other components removed during the process.

Step 10: Prime the Fuel System

• Cycle the ignition to prime the fuel system. Do this several times until you ensure fuel is reaching the injectors.
• Check for any leaks around the fuel lines and rails.

Step 11: Program the Injectors

• Using a diagnostic tool, enter the new injector flow rates. Photograph the injector numbers for reference.
• Follow the steps on your diagnostic tool to complete the programming.

Conclusion

After completing these steps, your 6.6 Duramax should be ready to run smoothly with the new CP4 pump, injectors, fuel rails, and lines. Don’t forget to check all connections for leaks and ensure the coolant system is properly filled. Finally, take the vehicle for a test drive to confirm everything is functioning correctly. If you encounter any issues, refer back to this guide or consult a professional mechanic for assistance.