How to Test Fuel Injectors

January 31, 2022 4:44 pm Published by Leave your thoughts

If your engine is not running as smoothly as it should and is idling roughly, if your truck won’t start or stalls out when attempting to start, or if you’re getting fewer miles per gallon, you may have a problem with the fuel injectors in your truck. The fuel injector plays an important role in your engine. They help to ensure that the right amount of fuel is injected into the cylinder. When the fuel combines with air, it creates a fuel-air mixture that powers the engine. When the fuel injectors are going bad or are already bad, you may experience some of the problems listed above. Here are a few of the easiest ways to test out your fuel injectors. 

A Simple Listening Test

On certain diesel engines, The first way to test out your fuel injectors is through a simple listening test. Anytime you are doing any tests on the fuel injectors or engines, you should allow the engine to cool. Once that is done, you can proceed to complete the tests you need. The first step to this test is to pop your hood and locate the fuel injectors. Familiarize yourself with their location before completing this test or any other test.

Turn your engine on, and then place a long screwdriver or long metal rod against the fuel injector. The metal tip of the screwdriver should be on the fuel injector, not your ear. Place the metal rod or screwdriver to your ear and listen for popping or clicking sounds. Complete this process with every fuel injector. If you hear popping sounds, you know the injectors are active and functioning. If you do not hear popping sounds, you have identified one or more fuel injectors that are not working and need to be replaced. 

A Voltage Test

The next way to test your fuel injectors is by completing a voltage test. To start this test, you will need to turn your truck on, but not turn the engine on. Turn the key until the electrical system turns on, such as the radio and lights, but do not crank the engine on. You can damage the engine or harm yourself if the engine is running, so it is important to understand that you only want the vehicle’s electrical system running for this test. 

Now that the electrical system in your truck is on, connect the alligator clip of a test light to the negative terminal on your battery. This supplies power to the test light tool. From there, take the pointed tip of the test light and touch it to the small part of exposed wire on the injector connector. The test light should light up, indicating the wiring is receiving the power it needs. Complete this process every fuel injector in your vehicle. If a wire does not work, the fuel injector needs to be replaced. 

A Leak Test

The final way to check for bad fuel injectors is actually the simplest. A fuel injector will need to be replaced if the O-ring is wearing out or is not holding its seal firmly in place. If the O-ring of a fuel injector is wearing out, you may notice leaks in or around the fuel injectors. Simply open up the hood of your vehicle, grab a flashlight or use the light on the back of your cellphone, and look around each of the fuel injectors. If you see any signs of leaks, such as fluid, around any of the fuel injectors, that fuel injector should be checked out or replaced. 

Purchase Replacement Fuel Injectors

Fuel injectors play a vital role in the operation of diesel engines. If you have tested out your fuel injectors and have determined that they are going bad, you will need to order new ones. Thompson Diesel Inc. carries all of the fuel injectors you will need. Contact us today to place an order for replacement fuel injectors. 


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