Symptoms of a Bad Diesel Injector – Causes & Preventions

The diesel injector is a part of the diesel injection system that supplies fuel to the engine. When the injector is bad, the fuel supply to the engine will be affected.

In addition, the damage to the injector will determine the symptoms to be expected. For instance, if the fuel injector is clogged, the engine will not start, there is loss of engine power and more.

Also, if the damage to the injector is a broken seal or nozzle, you should expect an abnormal consumption of fuel, engine misfiring, and more.

However, the injector is expected to last for a long period which could be between 100,000 to 150,000. How the injector is used and managed can affect its lifespan. Using low-quality fuel and not checking and cleaning the injector could shorten its lifespan.

how to test diesel fuel injectors

What are the Diesel Injectors?

The diesel injector delivers precise diesel to the engine’s combustion chamber. When we talk about the injector, it encompasses the whole injector assembly.

Parts of the injector include the injection nozzle, nozzle needle, pressure pin, nozzle spring, and many more.

There are two major types of injectors used by the diesel injection system, and they include.

Continuous injection

Fuel is squirted into the inlet port while the engine is running. In this case, the injector nozzle continuously sprays diesel into the combustion chamber. It also controls the amount of diesel going into the engine. It does this through the help of a mechanical or electrical control unit which reduces or increases the amount of fuel sprayed.

Continuous injection is used mainly in direct injection systems. In this type of injection, diesel is sprayed continuously into the combustion chamber.  

Timed injection

In timed injection, diesel is not sprayed continuously; instead, it is released in bursts in conjunction with the induction stroke of the cylinder. The spray action can be controlled mechanically or electronically. It is mainly used in an indirect injection.

What are the types of Diesel injection? Diesel injection is divided into 2 types: Direct Injection and Indirect injection. These types of injection help a wide range of diesel engines cope with diverse fuel needs.

Indirect Injection

Diesel engines do not make use of spark plugs, unlike gas engines. It is because diesel has a lower self-ignition temperature. To ignite the fuel, pressure is increased, which heats the fuel, and then it is ignited.

How does an indirect diesel injection work? Firstly, in an indirect injection system, the injection sprays the diesel in a separate chamber called the prechamber. The glow plug will heat the area during cold starts in the chamber.

Once the diesel is in the prechamber, it gets heated up and then mixes with fast-moving air thanks to the swirl motion by the piston. After a while, the piston will further compress the mixture, igniting it due to increased pressure and temperature.  

The ignited air and fuel mixture is then forced into the main combustion chamber to power the engine.

In this case, the diesel injector does not inject fuel directly into the main combustion chamber; instead, it is injected in another chamber. It is then ignited in the prechamber and moved to the main chamber.

Direct Injection

In this case, the diesel injector will spray diesel directly into the combustion chamber. There will be no need for a glow plug as the cooling surface is reasonably small.

Once the injector sprays the diesel in the combustion chamber, the air enters the chamber through the intake valve. In this case, a better air-fuel mixture will be achieved.

Read Also: The Best Fuel Injector Cleaners.

What are the symptoms of bad diesel injectors?

When the diesel injector is bad, the engine will not be able to receive an accurate amount of fuel. Depending on the type of damage, the engine might receive less or too much fuel.

For instance, a burst injection, when damaged, could continuously release diesel into an indirect diesel injection system. It could cause issues like engine misfiring and abnormal fuel consumption.

Below are common symptoms of a bad diesel injector.

Engine misfire

The engine will misfire when the injector fails to supply the right fuel. It could be caused by a clogged or partially clogged injector. It prevents the flow of the injector valve from closing correctly.

When the injector is clogged, your engine will not receive an accurate fuel and air mixture. This will cause sputtering and vibration from the engine.

Abnormal fuel consumption

When your fuel consumes more fuel than usual, it could be a sign of a damaged diesel injector. For instance, if the nozzle of the injector is cracked, more fuel will leak into the engine combustion chamber.

A problem like this will lead to the engine burning more fuel than it needs. As a result, the engine will consume more fuel.

Fluctuation in engine power

The power created by the engine depends on the amount of fuel entry into the engine. If the diesel injector is clogged, the engine will receive little or no fuel.

If the fuel going to the engine is little then the engine will generate low power for the vehicle to use. However, if the diesel increases so will the power generated by the engine.

Fuel smell

A damaged fuel injection could cause the injector to leak fuel. The fuel will leak from the injector nozzle or around the seal at the tip.

Fuel injects hold a high amount if pressure, and when parts of the injector is worn out the pressure and fuel will escape. Strong fuel smell coming from the engine bay will be evident. As the leak becomes larger, the smell will become more significant. 

Starting issues

When the injector is damaged, there are instances where diesel is not supplied to the engine at all. Fuel is an essential part of the ignition process. Without fuel, the engine will not start.

When the diesel injector does not supply any diesel to the engine to be ignited, the engine will not start. A blocked injector could be the sole cause of no fuel going to the engine.

Leaking fuel

Leaking fuel could be symptoms of a bad diesel injector seal. The seal provides a tight protection in the injector that ensures fuel does not escape from it when functioning.

When the injector seal is damaged, there will be leaks coming from the connections.  

Increased fuel consumption could be a leaking injector symptom.

What causes diesel injector failure earlier

What is the common cause of injector failure? The answer is the quality of fuel and contamination. Whatever can get into the fuel can affect the fuel injector.

Below are some of the factors that could cause an injector failure.

Contaminated fuel

The leading cause of damaged diesel injectors is foreign objects or substances in the diesel. Sometimes impurities like dust, sand, water, and rust can get into the fuel. They can get past the filter and then accumulate in the fuel injector.

Once the contaminants get to the injector, they could clog it up. Contaminants like water could cause severe damage once it gets to the engine system.

Poor fuel quality

Poor fuel quality can cause damage to the internal components by leaving large deposits like carbon and sludge in the injector. The deposit will accumulate in the injector and then cause it to get clogged.

A large amount of deposits

Different types of deposits can affect the injector. They include large amounts of sludge and carbon caused by fuel going through the injector and unburnt fuel leak leaks, which find their way to the external part of the injector.

Also, there is sediment buildup that affects the injector, which is caused by sand, dust, rust, and other forms of debris.

Worn-out internal parts

The injector’s internal components can wear out like other vehicle parts. It could be due to old age, rust, and other factors. Parts like the seal, when worn out, will create room for leaks and loss of pressure.

Injector solenoid failure

The injector solenoid is an electrical device that controls the valve. Like many other electrical components, the solenoid can get damaged. Once that happens, the valve will be stuck on close, and fuel will not flow through the injector system.

Due to the continuous power received by the coil, it could easily get damaged. When this happens, the injector will have to be replaced.

How to Prevent Diesel Injector Early Failure

Adopting a good maintenance culture for your diesel injector is one way to prevent the injector from failing early.

Below are tips to prevent early diesel injector failure.

  • Use fuel additives and lubricants.
  • Regularly clean the injector and remove the substances that can clog it.
  • Change the oil and filter at the recommended interval.
  • Always have a repair kit for the injector.
  • Change the fuel filter at the recommended interval.
  • Only use high-quality fuel.
  • Add oil cleaner to the oil system.

Running diesel with a bad injector can eventually cause engine failure if the issue is not resolved.

How do you test a diesel injector?

How long does a diesel Injector last?

The average lifespan of a diesel injector is usually around 100,000 miles. However, the injector can last up to 150,000 miles.

However, how long the injector lasts depends on many factors, like the fuel quality you use and how well the injector is maintained. Furthermore, if any of the main parts of the injector get clogged, like the injector body or nozzle, the injector is affected.

How much does it cost to replace diesel Injectors?

Depending on various factors, replacing a diesel injector will cost between $350 and $1,000. The cost excludes labor, which will be between $150 and $400, depending on the mechanic choice and the extent of repair.

If any part of the injector is damaged, the whole injector needs to be changed. The parts of the injector are not sold individually.

Also, your vehicle model will determine the cost of replacing the injector. If you drive a luxurious car, expect to spend more on replacement.

Final Words

Consider using fuel additives with your vehicle; they contain detergent that helps clean the tank and injector of dangerous deposits. There are also lubricants that help improve the engine quality and protect the iron parts of the tank, injector, and engine from corrosion. You can find fuel additives that also provide lubrication services. 

Akindayini Temiloluwa

I am passionate about everything automotive. Right from when I got my first toy car as a kid, I developed an interest in the inner workings of vehicles. As I grew up, my love for mechanical stuff became more substantial enough for me to pursue a career in it. My goal as an automotive content writer is to simplify the most challenging concepts for my readers, help them self-diagnose what may be wrong with their vehicles and offer real value for their time.

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