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Fuel Injector: How to Diagnose the Problems

Here's where you can get a thorough understanding of the fuel injector
In this article, you’ll learn about the fuel injector

Let’s get you trained up today in the art of “How to Diagnose Fuel Injector Problems”

Do you have a car that you use and abuse daily?


Don’t forget that with great vehicles, comes great responsibility.

The responsibility to stay on track with the manufacturer recommended maintenance intervals. Then to apply preventive care and maintenance, especially when driving a lot in stop-and-go traffic.

How to Diagnose Fuel Injector Problems
Credit: commons.wikimedia.org

The more moving parts and computer-controlled electronics your car or truck has, the more likely it is to have components that will show signs of wear.

Including corrosion or other malfunctions requiring repairs that could add up to more than you may have anticipated.

Luckily, before these events occur, your rig will start giving out little hints that can help to diagnose a problem.

People all over the country complain about the experiences they have had with automotive shops with unscrupulous technicians and service writers.

Next time, they will do their own research first, before taking their vehicle in for repairs.

What Does a Fuel Injector Do?

Bosch common rail injector
Constant adjusting helps keep the performance and consumption at normal levels and deliver the best efficiency possible
Credit: commons.wikimedia.org

Your car uses an internal combustion process to squeeze out power from these two main ingredients – oxygen and fuel. Oxygen comes in through an air intake system and usually fluctuates.

This behavior obliges the fuel injection system to constantly adjust the amount of gasoline it delivers for your ride.

Constant adjusting helps keep the performance and consumption at normal levels and deliver the best efficiency possible.

Injector Problems? How Do I Know I’m Having Them?

The most common symptoms that daily drivers encounter is the feeling that the vehicle is performing sluggishly with a lack of power, while also registering a drop in MPG (miles per gallon).

As a confirmation, the check-engine light may come on the dashboard and it’s time for you to have things looked at.

Common Fuel Injector Problems and Symptoms

Fuel injector issues can be of two types: a type that can be corrected, and a type that requires replacement.

Based on what you’re experiencing, you can easily conclude if it’s repairable or not.

Dirty Fuel Injectors

Any change in the way the injector sprays into the intake manifold can generate residue on the injectors.

Due to the high temperatures and ongoing friction, this residue can burn and form a crust on the injector making it harder to function correctly.

Usually, symptoms are inconsistent with engine power, poor throttle response and uneven engine idling.

Clogged Fuel Injectors

When your fuel comes from the refinery and is delivered by truck to the station… it usually passes a few ‘system checks’ along the way.

It also opens the way for different tiny objects and residues such as rust that eventually build up and clog the injector, leading to a poor supply of fuel in the cylinder.

Fuel Injector Not Opening

There is a chance you might get a rusted fuel injector or a condition where the windings break, which in exchange makes the fuel injector valve fail to open and deliver gasoline.

Usual symptoms include engine misfires.

Fuel Injector Not Closing

A faulty spring or rust buildup can prevent the fuel injector valve to close, leading to a gasoline leak inside the cylinder.

Usual symptoms are strong gasoline smell combined with low gas mileage.

Experiencing Any of the Above? Run Diagnostic Tests!

You can get your car connected to a diagnosis tool or run a few relatively simple tests.

However, they will require some diagnostic tools to complete.

Measure Temperatures from Your Exhaust Manifold

Depending on the type of problem you encounter (fuel injector valve not opening or not closing) your manifold temperatures with either will be very high or very low vs normal.

Injector not closing = overheat and burn out – usual temperatures over 600 °F;

Injector not opening = low temperature at the exhaust manifold – usual temperatures between 200-250 °F.

You can use a laser thermometer aimed at the exhaust manifold pipes while the engine is warm. Normal readings should be between 450-480 °F.

Listen to Your Fuel Injectors

Using an engine stethoscope, you can listen to each fuel injector.

Proper functioning should yield a sharp clicking sound, the absence of this indicates a problem.

Visually inspecting the Fuel Injectors

This can be done at home by simply removing the fuel injectors and inspecting.

You need to detach the fuel rails and then remove each injector to view for signs of damage or cracks within the injectors.

Make sure to protect your eyes and hands because fuel will flow from the rails when disconnecting.

Read more: Cold Air Intake: Pros and Cons for your Car


Did any of the steps above help you discover the root of your problem?

If yes… that’s great.

That means you know what you need to do in order to fix the problem.

No! Unfortunately, that means you might have to reach out to an expert to have a look at your engine and associated computer-controlled electronics.

A rule of thumb in the auto industry is to prevent instead of fix.

Regardless of which conclusion you came to after reading this article and performing these tests, it would be best to use a fuel additive that really works to remove carbon deposits.

These quality fuel additives will also make sure that your fuel stays clean, your injectors don’t get clogged up or overheated, plus ensure that your used and abused car always runs at its best.

CleanBoost® Maxx™ is a fuel additive that doubles as a combustion catalyst to improve performance and keep your components clean and free of carbon deposits.

CleanBoost® Maxx™ is a cost-effective way to treat fuel. Just 1 oz. treats up to 30 gallons & it will maximize both performance and fuel economy while reducing emissions as third-party testing proves.

Because the fuel will burn cleaner, it will result in fewer carbon deposits on internal components including the fuel injectors and EGR valves.

Read more: P0169 Wrong Fuel Composition Diagnostic Trouble Code Explained


Tim MillerFounderOBD Advisor

I’m Tim Miller from Denver, Colorado. I’m the founder of obdadvisor.com, an automotive blog about "Auto Diagnostic Tools and Repair Guides". My fan page is facebook.com/autozikcom. I've been working as an automotive mechanic and blogger for over 10 years writing articles to share my experiences and expertise.

Web: https://www.obdadvisor.comEmail: [email protected]
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