How to Test Fuel Injectors? Different Methods to Apply

Fuel injectors are very important parts of car engines. They provide the required amount of fuel for the engine cylinders. If they go bad, there can be performance loss in your engine. Because of this reason, you may want to test the fuel injectors of your car engine. Here you can find different methods to test your fuel injectors.

How Does a Fuel Injector System Work?

How to Test Fuel Injectors
Testing and examining the fuel injectors. Image Source:

Before starting this guide, we need to explain the general methods that you can apply to test the fuel injector system of your car. You can find the place of the fuel injectors near your engine. The number of injectors is generally equal to the number of cylinders you have. These injectors are generally connected with a rail that provides high-pressure fuel.

And they are connected to an electrical cable that provides the required voltage to work. Once the voltage comes to the injector, the injector releases the required amount of fuel to the engine cylinders.

So there is a negative cable and a positive cable. The electricity comes from the negative connection and goes from the positive connection.

Different Methods to Test Your Fuel Injectors

With this extensive guide, you will learn how to test your fuel injection systems effectively. And it will be very easy for you to test the system with one of these methods.

Testing the Fuel Injectors with the Listening Method

This is one of the most basic methods that you can make. And you can easily understand the faulty fuel injector system in your car. You just need to follow these steps to make this test.

  • First of all, we need to state that you need to take all the safety precautions that you need. Wear your safety glasses and cut-resistant gloves while you are dealing with the engine parts. The fuel injector system is a system that provides high-pressure fuel to the rail. So, the high-pressure fuel leak can harm your eyes and hands.
  • Find the place for the fuel injector serials. They are generally placed near the engine block, on the engine cylinders. And they are attached to a rail.
  • In this step, you will need hearing equipment. A doctor’s stethoscope will be very useful to hear the sounds coming from the injectors. But you may not have it. Also, a 30-35 cm metal rod will be very helpful.
  • Place the tip of the rod or stethoscope on the fuel injector and put your ear on the other tip of the rod. And try to hear the clicking sounds coming from the fuel injector. This clicking sound means, the injector provides the required amount of fuel.
  • And repeat this process for all the fuel injectors. If there is no sound coming from the fuel injector system, this injector is faulty.

Testing the Fuel Injector Electricity

If you are familiar with the basic electricity techniques, you can test the fuel injector electricity with a very basic device called a test light. It is a device that gives light if the system receives electricity. You can test the fuel injector systems if they receive electricity from the battery.

  • First of all, you need to open the electricity of the car by attaching the car key and turning it only to open the electrical system. Do not start the motor by turning it fully.
  • After that, attach the alligator clamp of the test light to the negative pole of the car battery.
  • After attaching it, you need to touch the bare cable of the negative side of the fuel injection that you want to test. To do it, you can open a small incision through the protective coating on the cable with a knife to test. And touch the tip of the test light and see if the light is on constantly.
  • If the light is on, it means you do not have a problem with the electrical connection. But if you can not see the light coming from the tester, it means it has a problem with the negative cable connection. Repeat the process for all the fuel injectors to see if you have a problem.

Test the Positive Electricity Output from Fuel Injector

how to test fuel injector?
A fuel injector system. Image Source:

By using the same tester, you can easily test the positive side of the fuel injectors. You need to follow the steps below.

  • First of all, you need to have a partner to run the engine. Each time that you touch on a fuel injector, the assistant must crank the engine.
  • Attach the alligator clamp to the positive pole of the car battery. You can see the negative and positive poles that are very straightforward on the battery.
  • And you need to touch the positive cables of the fuel injector that you are testing.
  • If the light of the light tester flickers, there is no problem with the fuel injector system.
  • You need to repeat this process respectively to find the problematic part. If there is no flickering light, this means the fuel injector system receives electricity but it does not receive the command coming from the ECU.

Testing the Fuel Injectors by Removing

The engine probably will not start if there is a faulty fuel injector. This is also a very basic test that you can apply. But, apply it if the engine does not start.

  • You need to remove the cover of the air cleaner housing. And you will be able to see the spray pattern of the fuel injectors.
  • Ask your assistant to crank the engine and see the spray pattern of the fuel injectors. If there is an injector system that does not provide the spraying, you can understand that it is the problematic part.

Testing with Multimeter

Also testing the injector electrical system is a very easy thing to do. What you need to do is, you need to test the resistance between the two poles of the fuel injector. Follow these steps to do it.

  • Multimeters have two probes that you need to place on the terminals to see the resistance.
  • You need to look at the car’s owner’s manual to get the information about the ideal ohm range that you need to expect from the injectors.
  • Adjust the ohm value on the multimeters to the unit that the owner’s manual states.
  • Unplug the electrical connections of the fuel injector that you want to test.
  • And place the multimeter problems on these terminals. It does not matter the places of the probes. Just place them randomly.
  • Check the ohm reading on the multimeter. If the reading is not within the range that the owner’s manual states, you have a problem with that fuel injector.

Testing with Fuel Injector Testers

Also, there are special fuel injection tester kits that you can use. But it is a more professional way. And you can only find these kits in different kinds of garages and mechanic places. We can explain the use of handheld fuel injection testers.

  • In general, these applications can only test one fuel injector. You need to specify the fuel injector to test it with these devices.
  • You need to disconnect the wire connections from the fuel injector.
  • Connect the fuel injector according to the user’s manual. And connect it with the fuel injector.
  • After the connection, open the electronic interface of the tester. Choose the correct type of injector and implement the test.
  • The tester will simulate the ECU system and send signals to test them. It will measure the performance of the injector. And it is very easy to understand if there is a problem with the fuel injector system that you have.

Conclusion on How to Test Fuel Injectors

So these are the general ways to test the fuel injectors. And you can easily understand the problematic one and you can change it with a new application.

If you have additional comments and questions about how to test fuel injectors, leave them below.

Check the other related topics about the fuel systems of cars;

Fuel Filter Wrench – Different Models

Fuel Tank Strap – Questions and Answers

Uğur Uygun

Hello everyone, I am Uğur. I am a mechanical engineer who has experience in different R&D departments of HVAC companies. With my best friend, I decided to build this website to share out knowledge and experience. And also, I am interested in automotive. So, I am writing about automotive and automotive-related articles here. Sharing my knowledge and experiences on these topics is a very big pleasure for me. I am willing to answer all of the questions people have about these topics.

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