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How to Test a Diesel Injection Pump

Posted by Scott Goldfarb on

Injection pumps are one of the main components of any modern vehicle. Whether you own a passenger car, commercial or industrial vehicle, or a pick-up truck, you can’t expect it to run without an injection pump. So, you need to know how to test a diesel injection pump to ensure it works flawlessly.

Since we’re aware that many new car owners aren’t familiar with the intricate parts of their vehicles, we’ll keep it as simple as possible. You'll be aware of your car's overall condition by explaining processes like fuel delivery, pump calibration, and pressure measurement. 

By understanding the evaluation of this component, you’ll ensure that you don’t run into any problems while using your vehicle. We believe that no one wants to deliberately put their life and those of others at risk due to a faulty car part.

Continue reading to discover how to test a mechanical diesel injection pump and its importance!

Diesel Injection Pump

Source: shutterstock.com/ Photo Contributor: Aleksandr178

The Use of a Diesel Injection Pump

Have you noticed that your car requires new diesel parts but aren’t sure of their quality? Check the article to discover how to test a diesel injection pump!

Before diving into diesel injection pump testing, you must first understand what this part is used for.

Most internal combustion engines need a fuel injection pump to operate in their fuel delivery system. These ICE or IC engines are also known as heat engines because they combine fuel with an oxidizer like air. The fusion happens in a combustion chamber, giving the vehicle power.

As for the fuel delivery system, it consists of the fuel tank, injector, pump, and filter. The main function of the pumps is to take fuel from the tank and deliver it to the combustion chamber. 

That’s why it’s usually located near or inside the fuel tank. To ensure the quality of the fuel, it also passes through a filter which purifies it and eliminates any containment. 

However, the diesel injection pump has a second function not many know. Since diesel engines don’t have spark plugs to ignite the fuel, the combustion comes from the highly-compressed air. While the pump’s main function is to get the fuel, its second is to provide compressed air. 

So, when the heat from the compressed air comes in contact with the fuel, your car starts moving.

How to Test a Diesel Injection Pump

When it comes to checking diesel pump performance, there are several ways you can go about it. While you may find professional services for a fair price, you can also do the testing yourself. But before you begin the process, you must know that it can be really dangerous if you don’t have prior experience.

When dealing with a fuel injection pump, you’ll be working in a high-pressure environment. Since the pump develops incredible pressure at about 15,000 psi, the fuel will leave the injector at approximately 3,000 psi. 

Therefore, the pumped fuel can easily cut through your clothing and skin if you come in the way. This can cause severe medical conditions that can lead to amputation and even death.

Now that you know the risks of this process, we recommend you always apply the needed safety measures if you plan on doing the calibration yourself. If you don’t feel comfortable with the experience you have, always turn to a professional service. This doesn’t only ensure your safety but also the best results.

Steps for Testing Injection Pump

After informing you about the potential risks, here’s what the step-by-step guide on testing diesel injection pumps consists of:

  • Take safety measures
  • Checking fuel pressure
  • Checking fuel delivery
  • Comparing with the manufacturer's specification

Take safety measures

The first step in checking diesel pump performance is to take the necessary safety measures. Besides the potential injury risks, you must also watch out for fire hazards. Remember that fuel is a highly flammable material that shouldn’t be taken lightly. Thus, we recommend you have the essential fire safety equipment at hand.

Some of the equipment pieces you may want to invest in for this process are the following:

  • Fire extinguisher
  • Safety glasses and gloves
  • Cleaning materials
  • Glass caddy or can

Before you begin testing the diesel injection pump, you must first find a suitable area to do it in. We recommend well-ventilated spaces without any incandescent light bulbs. You should avoid smoking in the selected area at all costs. Leave your lighters or pilot lights behind to avoid accidentally igniting the fuel.

If any spills happen, you should always clean them immediately. So, place the cleaning material at hand reach to act fast. Furthermore, any fuel you get out should be safely stored in glass containers. This can either be a glass can or a caddy.

Lastly, always ensure you relieve fuel pressure before opening the fuel system. Failing to do so may lead to fires and injury because the fuel will be released under pressure.

Checking fuel pressure

The next step in the diesel injection pump testing is to check the fuel pressure. To successfully do this, you’ll need three main pieces of equipment. These are:

  • Low-pressure gauge
  • Low-pressure gauge connection tube
  • Connection adapter

After attaining the required pieces, you should focus on the installation method.

The first step is to disconnect the low-pressure fuel line quick connector. Then, you insert the connection adapter into it. Once the connection adapter is safely installed, you can connect the low-pressure gauge connection tube. Lastly, place the low-pressure fuel line on the other end of the tube.

After doing so, insert the low-pressure gauge in its designated place on the tube and begin testing. For a static test, turn the car on and start the ignition. If you can’t start the vehicle's engine, you can crank it for five seconds. Then, you can leave the car and check the readings on the low-pressure gauge. 

As for the dynamic test, you should start the engine again and then leave it idle. After a few seconds of idling, you can check the pressure changes on the gauge again. Once you’ve gotten the proper readings, you can move on to the next test.

Checking fuel delivery

The second test you should do is check the fuel delivery. You’ll need either a flowmeter or a measuring container for this process. Since a flowmeter is usually a piece of equipment found in repair facilities, it may be difficult to get your hands on it. 

That’s why most people go for measuring containers. The best material for this purpose is glass because the fuel can fog up anything that’s made from plastic. 

The basic concept of a time fuel test is to see how much fuel you can get out in a specific timeframe. We recommend starting with a simple five-second time window to avoid fuel spillage. 

It’s best to do this while the car engine is idle alongside a friend or colleague. This way, you can ensure the fuel is dripping in the container while your helping hands turn the engine off when it’s time.

Checking fuel delivery

Source: shutterstock.com/ Photo Contributor: Nykonchuk Oleksii

Comparing with the manufacturer's specification

Once you’ve gathered the needed test results, you should always check the manufacturer's specifications. Remember that different car models have distinct readings and specific you should base your results on. 

You can define any problems that may have occurred with your vehicle only when you’ve compared the readings. 

Furthermore, depending on the numbers you get, you’ll know if you have a clogged filter and line or a fuel pump problem. By finding the real problem, you can better calculate the expenses you’ll have if you need to replace any failed parts.


After we’ve explained how to test a diesel injection pump, remember that you should always do this process with caution. 

If you don’t have any prior experience with car parts, always consult a professional service. Even though it may not sound complicated, failing to follow the safety protocols can lead to serious injuries and fires.

We hope this article has helped you understand step-by-step diesel injection pump testing and why it's so important!


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