Complete Diesel Fuel Injector Replacement Breakdown

Modern diesel engines have changed the way fuel is delivered. In the last decades, the PSI that is made by the fuel pump has increased dramatically. With this have come component failures and other complications.

You can imagine that at 20,000 PSI any trash causes damage. We now have 2 stage filters to mitigate this but none of the fewer injectors seem to be a serviceable part these days. with that, you likely will have a bad one at some point in the life of your diesel engine.

I surveyed 10 shops around the USA and come up with an average cost and average mileage at failure for diesel fuel injectors.

What Does It Cost To Replace Diesel Fuel Injectors?

On average, replacing a diesel engine fuel injector will cost $198 per injector. The price ranges between $155 to $240 and will change by part availability, location, and local cost of labor.

You will find that one of the most volatile factors in this cost is the shop hourly rate in your area. I could not believe how much it varied by the area I called. It was $115 per hour in Florida and $145 per hour in Maryland.

The time of year could also be a factor in cost. The wintertime parts and labor costs are generally higher.

How Often Do Fuel Injectors Need to Be Replaced?

As a general rule, diesel fuel injectors will need to be replaced between 150,000 to 250,000 miles. For the best performance, they should be inspected by a professional every 50,000 miles.

This will obviously vary depending on how you take care of your engine. factors like:

  • Regular oil changes
  • Injector cleaner periodically
  • Installing clean fuel
  • Replacing BOTH primary and secondary filters on the schedule

6 Signs and Symptoms of Bad Diesel Fuel Injectors

These were the most common complaints that lead to a fuel injector replacement according to my survey.

Check Engine Light

The most common cause of the visit to the shop will not surprise you. The MIL light was the main culprit. Today our vehicles are much smarter than we are. They know something is wrong sometimes before we even notice a difference in performance.

It is so important to know what the light is for. You really can’t ignore the Check engine light anymore. It will cost you more than you want to pay.

Hunting and Low Power.

The next cause was hunting or low power. Hunting is when your truck is “hunting” for fuel and the RPMs will go up and down as it receives fuel and then lower as it’s removed.

Low power is another main factor. In many places when trucks under a big load go to pull a hill a bad injector will make itself evident quickly.

Running rough

Rough idle was next on the list. When fuel is not delivered to the combustion chamber a the right time or not at all the engine will run rough. It will misfire and clang and bang around. We know that distinctive diesel roar and you can always tell when something is just off with it.

Cranking Issues

When fuel is not being delivered it can impede the engine from starting quickly or sometimes even to starting at all. If you are having cranking issues don’t assume injectors first. Take your time and diagnose the problem before jumping to conclusions. Of course, get it hooked up with your manufactures diagnostic software.

Bad Fuel Mileage

Many times when fuel economy is watched closely you can pick up on an injector issue quickly. Injectors play a huge part in fuel economy. After all, they are what deliver the fuel to be burned. So if you have a faulty or sticking injector you will begin to see less fuel mileage until the repair is made.

Rich Fuel Smell

This is very typical when you have a stuck open injector. It is just pouring fuel all the time and you get a rich fuel smell in the engine bay and the exhaust. This will likely accompany white smoke.

Should I get reman, refurbished, remanufactured, or new injectors?

A great article on the difference here can be found here. The cheap-skates of us will go with the cheapest option. The least expensive option will depend on your make and model. I prefer to have the original injectors worked and refurbished by a professional and return them to the engine when complete. I just think there is something to keeping the team together and keeping with what it came with.

This will not always be possible as sometimes there is damage or they fail the pressure and operational tests. In that case, they will need to be replaced. I would suggest a refurbished one from a reputable company.

Should I just replace the bad injector or all 8?

This is a great question but unfortunately, the answer is it will depend on your budget. As a whole, it will be better to replace all 8 injectors when you have one fail. If one injector is failing the other 7 are likely to follow suit. They were all manufactured at the same time. If you can afford it, it will save you money, time, and hassle.

Money does not always permit the best practices but it would be best if you are already having issues from one the rest are more likely to follow.

It is also a very good idea to go ahead and replace the injector wiring harness while you are in the crankcase. They often get brittle and begin to deteriorate about the same time the injectors start to fail. The heat and vibration get to everything in time.

Can I replace the injector myself?

Do you need to take it to the shop? Depends. If you have the tools and time and desire, replacing the injector or injectors yourself can be a good option. You can run into trouble with some manufacturers though.

I would highly suggest using the manufactures diagnostic software. Such as Insite for Cummins, ET for CAT, or ServiceMax for MAXforce. This will speed up the diagnosis and in some cases provide you with steps to repair.

An easy way to find out which injector is not working properly is to measure the temperature of the exhaust manifold at each cylinder. You are looking for a cooler temperature than the rest. This indicates that the fuel is not properly burning.

Some injectors like CAT require trim files to be uploaded to the ECM to operate correctly. Do your research and look online for a book for your specific engine.

How to replace a diesel injector: A general guide

Replacing diesel engine injectors can be a daunting task, but with the right tools and a sense of humor, it can be a breeze! Now, before we begin, this can be a complex and involved process that requires specialized tools and knowledge. The following is a general overview of the steps involved in replacing a diesel engine injector. Here are the basic steps to follow:

Preparing the vehicle:

The vehicle must be properly secured and supported, and the battery must be disconnected to prevent any electrical accidents. First, you’ll need to gather all of your tools and equipment. Make sure you have a good set of wrenches, a torque wrench, and a can of diesel injector cleaner. Oh, and don’t forget your trusty sense of humor. Trust me, you’re going to need it.

Removing the old injector:

This can be a tricky process, as the injectors are usually held in place with a retaining clip or bolt. But don’t worry, if you can’t find the clip or bolt, just remind yourself that “there’s a first time for everything.” The diesel engine injector is typically held in place by a retaining clip or bolt. The old injector must be removed by releasing the clip or bolt and carefully unscrewing the injector from the engine.

Cleaning the injector bore:

The injector bore is the hole in the engine where the injector sits. It is important to clean the bore thoroughly to remove any debris or corrosion that may have accumulated. This will ensure that the new injectors will have a clean and smooth surface to sit in. And if you happen to make a mess, just remember, “it’s not the end of the world, just the end of your clean engine.”

Inspecting the injector wiring harness:

The wiring harness connects to the rocker box and can develop shorts over time. Make sure your check its resistance and if it’s very old just replace it altogether.

Installing the new injector:

The new injector is carefully inserted into the injector bore. Make sure they are properly aligned and seated, and then use your torque wrench to tighten them to the proper specifications. And don’t worry if you over-tighten them, just remember “better too tight than too loose.”

Connecting the electrical connections:

The electrical connections to the injector must be re-connected, making sure that they are properly seated and tightened.

Testing the injector:

After the injector has been installed, it is important to test its operation to ensure that it is working properly. This can be done by using a diagnostic tool or by running the engine and observing the injector’s operation. And if you find that one of them is not working, just remind yourself “don’t worry, it’s only one out of six, you’re still batting .833!”

It’s important to note that replacing a diesel engine injector is a complex task that requires specialized tools and knowledge. It is highly recommended to seek the help of a professional mechanic.

Summing up

Injectors are essential parts of your engine. Keep up with your regular maintenance and save yourself some money and headache. A little maintenance goes a long way. I hope you get your injector issues solved and back on the road! Keep wrenchin.

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