Delphi DFI Injectors: Preventing Common Issues

Delphi DFi injectors are widely used in various engines, from JCBs to Great Walls and Holdens. However, a common challenge arises when technicians attempt to change the nozzle seals, only to find that the vehicle won't start afterward. This issue often occurs when air enters the system, preventing the injectors from firing.

Why This Happens

If air enters the injector system, the pressure required to purge it and get the injectors firing again far exceeds what a cranking engine can produce. At this point, the injectors need to be removed and tested on a bench by a fuel shop.

Preventing Air from Entering the Injectors

To avoid this situation, follow these critical steps:

1 - Disconnect the Injector Electrical Plugs

Ensure all injector electrical plugs are disconnected before proceeding.

2 - Fit High-Pressure Fuel Pipes

Attach the high-pressure fuel pipes but leave them loose at the injector connection.

3 - Prepare for Fuel Spillage

Place rags around the connections to absorb any spilled fuel.

4 - Purge the Air

Crank the engine to remove air from the system and ensure fuel is delivered to all injectors.

5 - Tighten Fuel Pipe Connections

Secure the fuel pipe connections to the injectors at approximately 27 Nm and clean up any spilled fuel.

6 - Reconnect Electrical Connections

Clean and reconnect the electrical connections.

7 - Start the Engine

Start the engine and briefly take it up to 2000 RPM two or three times.

8 - Check for Leaks

Let the engine idle and carefully inspect for any leaks.

Conclusion

While this process is important for Delphi DFi injectors, it’s a good practice to follow whenever a diesel fuel system is opened for repairs. By preventing air from entering the system, you avoid costly bench testing and keep the vehicle running smoothly. This process ensures the injectors perform at their best, reducing downtime and improving the reliability of the repair.