How to Bleed a Diesel Fuel Injector

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  • 2-4 hours
  • Advanced
  • 0-200
What You'll Need
Mechanics tools
Engine-handling equipment

To know how to bleed a diesel fuel injector, it is first important to know why the injector needs to be bled of air. A diesel fuel injector’s job is to carry fuel from the lift pump to the fuel gallery. While doing this, some fuel is sent to the combustion chambers. Excess fuel is used to cool down the injector lines and it goes back into the fuel tank. There can be an introduction of air bubbles during this whole process though if there has been a recent change of fuel filter or if the fuel runs out while the engine is running. When these air bubbles are formed, a diesel engine will refuse to start and run normally. This is why it needs to be bled of air. This step-by-step guide will help you to do that. A list of tools and materials required for this job is given below.

Step 1 - Check Fuel Filters

The first step is to ensure that the fuel filters have been installed correctly. Check the filters for clogging and examine the fuel lines from the tank to the lift pump to the fuel filters for leaks. Any holes through this whole line can cause an air leak.

Step 2 - Access the Fuel Lines

This step should be performed with close observation. Some vehicles come with engines that have their injectors exposed and these can be accessed easily and directly. Some engines come with injectors that are covered by a valve cover. Remove the valve cover using appropriate mechanic tools. It depends on the type of fastening the valve cover has. Choose a tool accordingly.

Step 3 - Open Fuel Cut-off Valve

fuel injectors

This depends on your vehicle manufacturer’s car specifications to an extent. Depending on your car specifications that you can look for in the manual, look for the injector that will give you fuel. This is usually the forward-most injector. Use a wrench to loosen the bolt on the last fuel injector.

Step 4 - Leak the Fuel

This step is fairly simple but you should practice caution while performing it. Loosen line connected to injector, and cover with a shop cloth. Rotate engine using starter until fuel comes out of loosened line. Tighten line and turn over engine with starter again. It should start and possibly run roughly for a few seconds as all the air bleeds out of fuel system. In extreme cases additional injector lines may need to be loosened until air is bled. When engine runs smoothly you have successfully bled the fuel system.

Step 5 - Clean up

After your job is done, cleaning up is really important again to avoid accidents and injury from the fuel on the ground. Use the rags to carefully soak up all the leaked fuel that is on the ground.