Everything You Need to Know About Diesel Fuel Injectors — Fuel Injector 101
Diesel Injectors
Fuel Injector

Everything You Need to Know About Diesel Fuel Injectors — Fuel Injector 101

We have covered quite a bit about diesel fuel injectors in our Fuel Injector 101 blog series. In this blog, we’ll be recapping some of the topics we have covered in previous blogs and answer other questions that come up often related to diesel fuel injectors. 

Note: If you have a very specific question related to your injector and want to skim past some of the other topics we cover, use the alt + F keys on your keyboard and see if we cover it at some point. 

Keep in mind that diesel fuel injectors vary per engine. We’ll try our best to cover broader topics related to injectors. We may also reference the Delphi injectors commonly used in the Doosan Bobcat engines. 

How Does an Injector Work? What Does an Injector Do?

Fuel injectors will vary based on what engine you are using them for, but they essentially measure the amount of air that goes into the engine, and determine how much fuel is required. 

Fuel from the injection pump will enter the injector’s body and start building pressure (approx 4000 psi). Once the pressure builds, the injector’s check valve opens off its seat and sprays fuel. Most engines use ECM’s to control and open the injectors nozzle. The nozzle is attached to the injector which sprays fuel directly into the air as soon as the valve opens. Excess fuel remaining after the valve is opened is then returned back out through the injector body, then back to the injection pump. Modern injector’s such as the ones that go into the Doosan D24, D18 and D34 engines are required to be coded to the ECU. 

Most injectors have about 15 main parts including the filter, guide ring, core spring, seat spring, seat, pole piece, stop, solenoid coil, solenoid body, core ring, core, spray tip, director and spray tip housing. As mentioned above, the fuel flow is controlled by the ECM by raising a ball off its seat. The fuel then flows through the seat orifice and out through a fixed director plate with several holes. The director plate directs the fuel spray pattern. These injectors typically have a 10 to 15 degree angle spray pattern. The fuel atomization of this type of injector is comparable to the disc type injector. Disc and ball type injectors tend to be less susceptible to clogging. (Referenced in our blog ‘How Diesel Fuel Injectors Work’)

Why Does an Injector Fail? Cause of Injector Failure? 

An injector can fail due to fuel contamination, a broken solenoid, fuel leakage, a cracked injector, water corrosion inside of the injector, improper installation or improper coding. Fuel contamination is the most common way that premature fuel injector failure occurs. Contamination can lead to a clogged injector. 

How Long Should My Fuel Injector Last? 

Depending on the type of fuel injector you are using, you should generally expect it to last between 50,000 to 100,000 miles. We have also seen some injectors last up to 200,000+ miles. The longevity of your fuel injector will be dependent on how well you care for your injectors and what kind of terrain your vehicle is put through. Frequent maintenance on your fuel injectors and fuel system (every ~250 hours) will be important to ensure they last you a long time to come. For more information on how long your fuel injector should last for, check out our other guide

How Do I Remove My Injector? 

The removal of injectors will vary based on your vehicle and engine. Regardless of what vehicle and engine you are using, make sure you clean any dirt or dust that could potentially fall into your engine and cause damage. For the Doosan Bobcat engine, start by removing the airbox and rubber caps. Pull off the PCV tube and remove the top cover that sits underneath the fuel lines. Next, you will need to unscrew and remove the fuel line associated with the injector you are removing. You will then need to remove the hold down clamp and bolt. Lastly, remove the safety lock and unplug your injector. Reference our complete guide on how to remove your fuel injector. 

Can Fuel Injectors Be Cleaned? How Do I Clean Them? 

Yes. Fuel injectors can and should be cleaned frequently. We recommended cleaning them every 10,000 to 20,000 miles. Reference our guide for how to clean injectors at home

How Do I Test My Fuel Injector?

If you believe you are having issues with one or all of your fuel injectors and would like to test them, follow this guide from several testing methods

What is the Difference Between Gasoline and Diesel Injectors? 

Gasoline is injected in the manifold and ignited in the cylinder. Diesel is injected directly into the cylinder and self ignites due to the pressure created.  

Do I Replace 1 or All of My Injectors? 

Generally, we recommend replacing all of your injectors unless you know which injector is faulty or if your injectors are fairly new. In some cases, it is not always easy to know which injector is bad. If your injectors have 50,000+ miles on them, we highly recommend replacing the entire set considering that these injectors will all need to be replaced soon. Replacing the entire set will ultimately save you time and money in the long run. 

Other FAQ’s 

What Fuel Injectors Do I Need? 

We recommend that you reference your owners manual or serial number. If you think we carry one of your parts, you can contact us with the part number and/or serial number so we can confirm. 

Can Fuel Injectors Cause Misfire? 

In some cases dirty and clogged fuel injectors can cause your engine to misfire. You will usually feel your vehicle vibrate first or notice a loss in power which can result in a pop sound. The misfire occurs when there is difficulty with the air and fuel mixture entering the engine. Dirty or clogged injectors are the most common reason for a misfire. There could be other causes such as a mechanical problem with your engine or ignition system, and imbalance in air and fuel delivery, sensor and module related issues or a broken control circuit. 

Can Fuel Injectors Be Repaired? 

In short, yes, fuel injectors can be repaired, but we don’t recommend it. Sending your fuel injector for repair can take a long time and potentially cost you more. Of course, price will vary per injector, but it may be more affordable to purchase new injectors. It is also not recommended to repair injectors at home. There are facilities that specialize in rebuilding injectors. 

Can Fuel Injectors Go Bad From Sitting? 

If you are working with a modern engine and injector it is rare for fuel injectors to go bad from sitting. On the other hand, if you are working with an older fuel system, they may be more likely to crack and leak over time from sitting. In some cases, your injectors may just need to be fired up with a battery voltage. 

Where Are Fuel Injectors Located? 

Most fuel injectors are located at the head of the engine intake manifold, under the fuel rail and near the valve.

How To Check For a Leaking Fuel Injector? 

One common way to know if your injector is leaking is if you notice a gas smell coming from your vehicle. You will want to conduct a nozzle pressure test on your fuel injector. If you conduct this test and find that your injector leaks, this could mean that the pintle inside of the nozzle is stuck upon. You can follow our guide on how to use a nozzle pressure tester to determine if your injector is leaking. 

Is Fuel Injector Cleaner Necessary? Is It Good For My Vehicle? Does it Work? 

Fuel injector is not necessary but highly recommended. Cleaner for your fuel injectors and fuel injection system is recommended especially if your engine is running rough or stalls. Cleaner won’t be the cure to an already faulty injector, but it can certainly help prevent your fuel injector from failing prematurely. 

Is Fuel Injector Cleaner the Same as Carburetor Cleaner? 

No, they are not the same. Both types of cleaners are used to clean different parts of your engine. A carburetor cleaner is used to displace the air and fuel mixture into a chamber, while a fuel injector cleaner is used to clean the fuel system including the fuel lines, inlets and outlets. Carburetor cleaners are NOT used for fuel injection systems. On the contrary, you CAN use fuel injector cleaner on a carburetor. 

Does a Bad Fuel Injector Affect Performance? 

Yes, a bad fuel injector can affect your engines performance, and could cause it to misfire. Poor fuel efficiency is another direct cause that can occur when your engine is running utilizing a bad fuel injector. 

Can Fuel Injectors Cause White Smoke? 

Yes. Signs of white smoke coming from the engine often points to a bad fuel injector. Typically, white smoke occurs when a lack of fuel improperly enters into the injectors body. White smoke can also be caused by coolant burning in your vehicle's combustion chamber.

What is an ECU? How Do You Code the Injector? 

An ECU is an Electronic Control Unit which tells the injector when and how long to fire. The ECU sets off precise and pressurized spray into the combustion chamber through its nozzles, causing ignition. Over time the ECU gets better at calibrating your injector so that it can control certain functions of the injector. If you have never coded an injector, we recommend you take your injector to a dealer. If you would like to code the injector yourself, you will need to have a programming kit which can be rented at diesellaptops.com. 

When Should I Replace My Fuel Injector O-Ring? 

You should replace your o-ring anytime you clean or replace a fuel injector. We include o-rings with all of our fuel injectors that fit with the Doosan Bobcat engines. 


Do you have any other questions or issues related to your fuel injector that is not covered here? Reach out to us and we can certainly help you get your question answered. As more questions arise, we’ll be sure to add them to this guide to assist others in the future. 

If you are looking to purchase new diesel fuel injectors for your vehicle, check out our catalog.