Fuel injector guide by expert mechanic

The innovation that leads to the development of the fuel injector was triggered by the need to develop a more efficient, affordable, less wasteful way for automobiles to function. In the 20th century, there was an increase in the demand for automobiles and the results of having so many vehicles on the road was a recipe for disaster.

That is when you consider fuel prices and emission levels. That's why in the 1920s, Bosch started the development of a device to combat these problems. That device would turn out to be a major game-changer in the field of combustion engines and it is called the fuel injector. This is what will be discussed in this article.

Injector overview

Fuel Injector

How does the injector work?

The fuel injector can be described as a regulatory system in the engine. It is a small nozzle electronically controlled device that is used to send in/ inject fuel into the engine at high pressure. It's this injection process that kickstarts the preparation for a proper air-fuel mixture which also stimulates effective combustion to the engine.

Basically, your injector works in tandem with the throttle position sensor of your vehicle in fuel and air regulation. How this works can be found in this article.

So it's safe to say that the effective running of the engine won't be possible without the input of the fuel injector. The process involved in the workings of a fuel injector might seem complex but in actuality, it's quite straightforward.

  • First of all, the fuel pump of the vehicle pushes the petrol or diesel fuel through the fuel lines into the injectors
Fuel injector pump
  • The engine control unit which serves as the brain of the engine then uses sensors to figure out and pinpoint the right time to fire the injectors and inject fuel into the combustion chamber
  • The engine control unit will proceed to activate the fuel injector. It's from the nozzles of the fuel injector that the pressurized fuel is sent into the combustion chamber.

However, the size of the injector's nozzles is small as a result, the fuel that comes out of them is atomized, and this is the reason for its effective burning.

Functions of the fuel injector

The injector is believed to be one of the greatest innovations in the automotive industry. The fuel injector has one major function and that is to spray or inject atomized fuel into the combustion chamber of an internal combustion engine.

As trivial-sounding, as it might seem, it is actually through this action that modern engines can give us the refined energy that we've grown accustomed to.

functions of a fuel injector

Before the invention of the injector, vehicles used only standard gasoline engines that were not only inefficient and expensive to maintain but were also bad for the environment. That's why a situation whereby your fuel injector develops a fault, can lead to lower performance and a list of other problems from your engine.

Signs and symptoms of a bad fuel injector

Like everything man-made, the fuel injector can develop faults or start to malfunction. And this fault can lead to the fuel injector developing performance issues. There are many reasons why your injector might become faulty.

One of which is because it has gotten clogged by debris or other electrical faults. Whatever might be the case, the resulting symptoms and signs are similar all around. Here's how to know if you have a bad fuel injector on your hands:

Misfiring engine

When the injector can't deliver the dose of fuel required by the engine control unit, maybe due to a blockage, it can lead to a case of engine misfiring. If at any point in time you notice your engine misfiring or a delay in response time after hitting the accelerator, then you might have a faulty fuel injector.

You should get it checked out as soon as possible or better yet ensure to keep the fuel injector from any clogging or blockage. This article gives in-depth information on the best injector cleaners.

Fuel leakage

Oftentimes, the sign of a fuel leak can be a strong indication of a faulty fuel injector. This is sometimes caused by a lack of proper maintenance of your vehicle. Perceiving fuel or suspecting a leak however is not a clear sign that you have a faulty fuel injector.

An appropriate level of knowledge about your car's fuel system otherwise known as the throttle system can help in diagnostic and you can find that in this article. If there are other accompanying symptoms, however, then it will be helpful to get it checked out.

Engine stalling

Fuel injector nozzle

Have you ever noticed your engine starting to stall or completely go off without you touching the ignition key? This may be a result of a faulty fuel injector.

When enough fuel isn't getting into the engine from the injectors, it might cause the engine to stall. Engine stalling can be a result of a blocked fuel injector nozzle or a leaking nozzle.

Poor fuel economy

One of the main reasons why the injector was invented in the first place was for better fuel economy management. However, a situation where the injector is faulty or bad will cause a poor fuel economy. Your engine control unit will require a certain dose of fuel from the injector which will be unable to supply enough because of the bad injector.

Check engine light

Check engine light

Probably the commonest and the most obvious sign of a bad fuel injector is the check engine light will appear on the vehicle's dashboard. The minute your car's injector isn't doing what it's supposed to do i.e., is not giving enough or it's giving too much fuel, the check engine light will appear.

However, just because the check engine light is turned on doesn't mean that the problem is always going to be the injectors. Still, it's s good sign to watch for.

What can cause the injector to fail?

There are only three possible reasons why the injector might fail

  • Mechanical reasons

The injector has several parts that move to ensure its job is being performed efficiently. Over time, however, there might be the occasional wearing down of these parts that will cause your injector to go bad.

  • Clogged or blocked nozzle

Dirt and debris can gather up in your injector nozzle causing it to malfunction as a result of the blockage. Getting an injector cleaning kit can help you in taking care of all the unnecessary guides. If you're unsure of what cleaning kit to get, this article can be your guide and you can see this article for a thorough explanation on how to clean your injector.

  • Leaks

The o ring which is the point where the injector meets the fuel rail can go bad over time due to excessive heat. As a result, the injector might start to leak which can further cause it to go bad.

Can you replace just one fuel injector?

Sometimes, it could be a single fuel injector that actually has a fault and not the entire bunch. Does that mean you can replace a single injector? Yes, you absolutely can.

The only problem is that it's not always advisable to do this. And you should consider your car's model as well as the cost. Especially the cost because some mechanics can charge a similar price as getting everything removed m

Should you change your car injector or repair it?

replacing a fuel injector

Most car replacement issues are a result of clogged nozzles (build-up of dirt or debris) or a leak (caused by a faulty o ring). This can easily be fixed by a thorough cleaning you can do yourself by following these guidelines.

Or you can simply replace the o ring (depending on the problem)The only incident where you'll need to replace your injector is if it's broken or damaged beyond repair. Unfortunately, replacing your injector might cost you a lot.

Will a bad fuel injector throw a code?

Like most car issues, your vehicle is likely to throw a code when it has a faulty fuel injector. For example, the check engine light will appear on the dashboard of your car another is the engine misfiring or stalling.

How do you know if you need a new fuel injector?

The car injector typically lasts from 50,000 to 100,000 miles and its life span can be affected by the kind of fuel being used (ie the quality)Failure to change the fuel injector can cause several issues that may severely damage the engine.

That being said, it's important to regularly clean and maintains your fuel injector to increase its warranty. However, you must change it immediately when the problem is not repairable for example a broken injector.

Do bad fuel injectors make noise?

A functional and good injector will make a steady clicking noise to indicate proper functioning. But a bad one will either make no noise or the sound won't follow a regular pattern.

Can you drive with a bad fuel injector?

You can still drive with a bad injector even though your car clearly won't be working at its optimum performance. However, like most car problems, it's never advisable to ignore the issue due to its relationship with the engine.

Meaning a prolonged use of a bad fuel injector can cause severe damage to the engine leading to a double problem for you and your vehicle. That's why it's important to tackle the issue as soon as it arises.

How many miles do fuel injector last before it goes bad?

 Bad fuel injector

The mileage your fuel injector has before it runs down depends on the model and the car brand as well as other factors such as the quality of gasoline in use.

However, on average, a typical fuel injector should go for 50,000 to 100,000 miles before it has run its warranty. That doesn't mean you shouldn't look into things when there are signs of possible damage.

You should check out your injectors and fix and repair them regardless of how many miles you've run with them.

What can cause a fuel injector not to spray?

Your injector might fail because of obvious reasons such as debris formation around the nozzle. The clogged nozzle will not be able to spray fuel into the combustion engine because of the build-up of dirt and other forms of debris.

There is another reason why your injector might not spray and that is a low / no fuel pressure. The injector should have about 1.3 ohms of resistance to function properly and spray effectively. A lack of it might cause it not to spray at all or spray very little.

Fuel injector FAQs

Do fuel injectors add horsepower?

People often think that because the injector is responsible for supplying and regulating fuel to the engine that it adds horsepower. This of course is a popular misconception. The injector doesn't add horsepower to your vehicle's engine, rather, it supports horsepower. Meaning the larger the flow rate of the fuel injector the more horsepower It's able to support.

Will the new fuel injector improve performance?

Replacing your fuel injectors might require you to break the bank that's why it's advisable to only replace them when they require replacement. But as a car owner, you will want to get the most out of your vehicle and you might consider replacing them with new ones.

New fuel injectors admittedly do affect the car but improving your car's performance. It can also reduce fuel emissions and increase the optimum performance of your vehicle. The only problem is you'll need to consult with the professionals to know what the best options are. As replacing them without knowing about them can actually lower your engine's performance.

Are fuel injectors universal?

Fuel injectors like other parts of your vehicle are specific to that particular car model. Meaning it's not a one size fits all situation. The right one for your vehicle must combine all the elements specific to your engine's needs.


Now that you know everything you need to know about your injector, you'll be better equipped with all the necessary information if it ever develops a fault and be able to give a proper diagnosis. Still, if you're a novice mechanic or car owner, it would be better if you consult with the professionals.

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