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How to Bleed Diesel Injector Pump

Posted by Scott Goldfarb on

The diesel injection pump is an engine component that delivers a precise amount of fuel to the combustion chamber. To keep its performance high, you must perform regular maintenance procedures as part of your engine care routine, including bleeding the injection pump. If you know how to bleed diesel injector pump, you’ll have the knowledge and skills to optimize the fuel supply to the engine.

Therefore, we will guide you on how to bleed the fuel system and help you achieve a more satisfying driving experience.

How to Bleed Diesel Injector Pump

Source: shutterstock.com/ Photo Contributor: Matveev Aleksandr

How to Bleed Diesel Injector Pump

First, you will need to identify the pump. Its design structure may vary depending on the model of the engine, but some common features can help you find it. The pump is cylindrical, with inlet and outlet ports where fuel lines connect. Many diesel injection pumps have a manual hand pump that looks like a lever or a plunger.

Once you find the injection pump, you must locate the bleeder screw. It is normally located on the injection pump, and it has a small screw that can be loosened to release air. If you follow the fuel lines, you will surely find it, as it’s usually positioned for easy access during bleeding.

Then, open the bleeding screw and use the hand pump to pump the fuel system until clear, bubble-free fuel flows from the bleeder screw. When finished, close the bleeder screw tightly again and start the engine to check the results of your work.

When to Bleed the Fuel System

The pump requires bleeding whenever air enters the fuel system. That can be after changing the fuel filters, running out of fuel completely, or when work’s been done on the fuel system that might allow air to enter the fuel lines.

While the reasons for bleeding the injection pump can vary, the goal is always to eliminate air bubbles from the fuel system and ensure the engine receives a steady supply of clean and well-pressurized fuel.

So, a refurbished fuel pump may cost you a lot less compared to a new one and give you just as good results. At Goldfarb & Associates, you can choose from many manufacturers, and our team of experts will help you find the best component for your engine.

Here are all the ways for how air can enter the fuel system:

1. Changing the fuel filters

This is the most common occurrence as fuel filters require changing every 10,000 to 30,000 miles, which means that most car owners perform this task every year. During the changing of the fuel filters, air can enter the system if the filters are not properly sealed or if there are air pockets in the filter housing.

2. Running out of fuel

If you drive your car until it completely runs out of fuel, you are creating the possibility for air to enter the system. When the tank is empty, it creates a vacuum in the fuel lines, which can draw air while you’re filling the tank.

3. Fuel system maintenance

Performing any kind of maintenance on the fuel system can sometimes lead to air entering the system. Repair work that requires components to be disconnected and reconnected is particularly susceptible to allowing air to enter the system. This is valid for tasks like replacing fuel lines, fuel injectors, or the fuel pump itself.

4. Fuel contamination

Sometimes, you can pour contaminated fuel into your car’s tank, leading to air bubbles forming in the fuel lines. The contaminated fuel can contain water or other impurities and disrupt the injection pump's proper functioning.

5. Leaks or loose fittings

Air can enter the fuel system if there are loose connections or leaks in the fuel lines. The fuel system operates under suction, and it relies on a vacuum to draw fuel from the tank to the engine. When there are leaks or loose fittings in the fuel system, air can be drawn into the system as it tries to pull fuel.

Important Considerations


When performing this procedure, it’s important to follow some safety precautions, like wearing protective gear and working in ventilated areas to prevent exposure to fuel fumes. 

Also, ensure the engine is off before starting the bleeding process to avoid the hazards of working with a running engine. It’s best to disconnect the battery to make sure there won’t be any accidental ignitions or electrical mishaps while working on your engine.


An important consideration is the possibility of fuel spillages during the bleeding process. You must have absorbent materials around, such as old rags, to quickly contain and clean up any fuel spillage before it makes a mess.

Potential issues

Even after bleeding, you may still have air in the system, which causes poor engine performance. In such cases, you must bleed the system again until all air gets removed. Ensure that the bleeder screw is tightly closed after each attempt, as it might be what’s letting air enter the system. A poorly closed bleeder screw may also cause fuel to leak and cause further damage as a result.

If the bleeder screw is too difficult to turn, consider using a different size wrench to avoid damaging the screw. If it’s excessively difficult to turn, regardless of the wrench size, apply penetrating oil and allow it to sit for a while before opening it again.

Additionally, bleeding can affect the timing of the injection pump if not done correctly, and you will need to adjust the timing accordingly afterward. If there are other issues like difficulties with starting the engine, you will need to do a thorough inspection to learn the reasons or seek professional help.

Potential issues

Source: shutterstock.com/ Photo Contributor: Vereshchagin Dmitry


Knowing how to bleed diesel injector pump can be a vital skill for diesel car owners as it will improve the car’s function and potentially save money and time. By removing the air from the fuel system, it improves fuel delivery, combustion, and overall engine performance.

The process involves locating the bleeding screw and carefully purging air from the system. Plus, regular maintenance can help prevent the need for frequent bleeding. Overall, if you need fuel injector pumps, we offer high-quality products. Reach out to us now, and we will help you!


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