How To Repair Your Diesel Fuel Injector

How To Repair Your Diesel Fuel Injector


A diesel fuel injector (also called a common-rail fuel injector or a unit injector) squirts a very high-pressure jet of diesel fuel into the combustion chamber of a diesel engine.

Its function is to control the amount of fuel delivered to the combustion chamber in proportion to the airflow entering the cylinder.

How To Repair Your Diesel Fuel Injector
How To Repair Your Diesel Fuel Injector

It also helps smooth the delivery of fuel into the engine by controlling the timing and duration of each injection. It works by opening and closing to allow pressurized fuel to pass through the nozzle.

The idea behind fuel injection (compared to older injection or carburetors) is to achieve a finer and more complete mix of air and fuel for complete combustion. This helps reduce emissions by burning most of the fuel in the combustion chamber.

As a result, a very high compression ratio is achieved, which provides unprecedented power and great fuel efficiency.

Making sure your diesel fuel injectors are in safe working order is a must if you want to maximize the performance of your diesel engine.

Sign That Indicates A Bad Diesel Fuel Injector

Several signs indicate a bad diesel fuel injector. Some of the main signs that play their part are as follows:

  • As diesel fuel injectors age over time, they can become clogged with deposits, which keeps fuel from flowing properly. This problem affects the quality of your machine’s output and the life of your diesel engine.
  • Another sign of a defective fuel injector is blue smoke on idle, which may vary in intensity on the first startup, but will gradually decrease as the engine warms up.
  • You can spot a bad injector by noticing changes in the pulse width. The pulse width is when it takes for the injector to open or close and must be within a certain range for proper performance.
  • The issue can be noticed by too much fuel addition by fuel injector to the cylinder, thus causing it to flood the cylinder and ruin the engine’s performance.
  • The main signs will be an excessively loud noise, vibration, and even misfiring that will seriously hinder transportation.
  • Poor idle, lack of power, and hard starting are all possible signs that you may have a failure of one or more of your diesel fuel injectors.
  • In some instances, you may experience a high exhaust temperature, and in some cases, the engine may stall.
  • You will experience a smelly exhaust while operating your excavator diesel engine. A leak of your diesel fuel injector may also be a cause of failure of your diesel fuel injector.

Trouble Shooting Your Diesel Fuel Injector

Repair Your Diesel Fuel Injector
Repair Your Diesel Fuel Injector

Troubleshooting means determining the cause for the malfunctioning of any device or machine. Is it not working as it should? Is there something wrong with its parts, its function, or both? The troubleshooting steps are different for each machine or device.


Troubleshooting is the process of eliminating possible sources of malfunctioning a diesel fuel injector. It includes visual inspection, testing, and elimination of each source until you have isolated the actual cause.

It involves the process to find out if the components of your diesel fuel injector are not working properly. Some of the main components of diesel fuel injector are as follows:

  • Valve Spring
  • Electromagnetic Coil
  • Pilot Needle
  • Return Spring
  • Fuel Return Line
  • Servo Piston
  • Nozzle Spring
  • Pressure Pin
  • Nozzle Needle
  • Injection Nozzle
  • Filter
  • Guide Ring
  • Spacer
  • Core Spring
  • Seat Spring
  • Solenoid Coil
  • Pole Piece
  • Core Ring
  • Spray Tip Housing
  • Director
  • Spray Tip

How to Repair Diesel Fuel Injector?

After troubleshooting, you can find out the cause of the malfunctioning of your diesel fuel injector. Now the thing you need to do is repair your diesel fuel injector.

There are two ways you can follow to get your diesel fuel injector repaired. Once to go to a professional technician and get your diesel fuel injector repaired. The other one to repair it yourself.

To repair your diesel fuel injector yourself, you need a toolkit that must contain every tool essential for carrying out the diesel fuel injector repair.

Now the thing you need to do is disassemble, open your diesel fuel injector with the help of a tool kit and determine which component is faulty. The faulty components can be anyone from the list of components depicted above.

The repairing process also depends on the intensity of damage that your diesel fuel injector was facing.

If the intensity of damage is small and is only confined to a few components, it can be repaired, and this will ultimately prevent you from spending extra cost on purchasing a new fuel injector.

Now, you need to replace the faulty component with the new one and then assemble all the components again and cope with the installation. This is how you can get your diesel fuel injector repaired.

Precautions to Follow While Repairing Your Diesel Fuel Injector

Preventive measures help you repair your diesel fuel injector effectively and efficiently and prevent any accidents. There are multiple preventive measures you can follow while repairing your diesel fuel injector. Some of the preventive measures are as follows:

  • First and foremost, power should be disconnected from the engine to be tested. Also, the diesel fuel injector should be removed from the injector body.
  • Make sure the injector remains cool while repairing it and clean the injector out completely. Prevent any foreign objects from entering your diesel fuel injector.
  • It would help ensure that the technician had adequate education and training to service diesel fuel injectors. This is to ensure that they understand the proper `and safe ways to handle and test diesel fuel injectors.
  • Keep your hands away from the electrical contacts as there may be high voltage present in the pump. Always wear latex gloves and proper clothes that are specially made for repairing purposes.
  • You never want to get injection fluid or any other diesel fluids into your eyes. Wear safety goggles to avoid this from happening.
  • While repairing, make sure to keep all the components in a single place. This will not result in the loss of any component.
  • Do not repair a diesel fuel injector in a place where there is any spark source. Sparks from a welding machine or any other source might ignite the leaking fuel oil.
  • Every component of the particular fuel injector needs to be marked to know its proper location once the parts are put back together again after their repairing process is over.

Cost of Repair

The cost varies depending on the model, make, and brand of your diesel vehicle. It also varies significantly depending on the type of injector that failed.

With upwards of 12 different nozzle sizes available for most diesel-fueled vehicles, thousands of different combinations of injectors are available for any vehicle application.

The cost of repairing your diesel fuel injector will also vary depending on which problem this is causing. Which components is the source of this malfunctioning?

The cost also depends on the expertise level of the technician, the cost of spare parts needed to get replaced, the extent of damage, the complexity of the diesel fuel injector.

How to Avoid Diesel Fuel Injector Repair?

How To Repair Your Diesel Fuel Injector
How To Repair Your Diesel Fuel Injector

The injector is a precision mechanical part. It needs to be careful in maintenance. Many car owners do not pay attention to the maintenance requirements of the diesel fuel injectors, which may lead to the diesel fuel injector repair.


You can follow the given steps to avoid diesel fuel injector repair:

  • Removing accumulated soot inside the fuel injectors once each year after prolonged periods of start-stop operation.
  • Diesel fuel injectors should be checked at every oil change, typically every change or 5,000 miles, depending on how much the vehicle is used.
  • Always use high-quality fuel in your diesel fuel injector to avoid clogging. The fluid having the characteristics of optimum viscosity, maintaining temperature, reducing friction must be used.
  • Hire a professional technician to get your diesel fuel injector repaired.

Final Words

A malfunctioning diesel fuel injector will harm your engine, not just hamper performance. You can’t achieve a top speed or complete fewer cycles without undependable diesel fuel injectors. As diesel fuel injectors play a major role in engine operation, it is very important to repair any defects as soon as possible.

Finding ways to cut back on your fuel costs can make a big difference when it comes to your fuel bills. Repairing your diesel fuel injector might be able to do just that.

Doing this will improve the efficiency and effectiveness of your diesel engine and save you more costs.

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