Signs of Bad Fuel Injectors

Signs of a Bad Fuel Injectors – What Needs to be Done?

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If you’re driving an auto that’s manufactured before the 1980s, then there are higher chances it’s equipped with a carburetor. But, for those motorists driving vehicles manufactured after the 1980s, then these cars are fitted with advanced fuel injection systems that have successfully replaced the traditional carburetor. Now, one part of this sophisticated fuel system is the fuel injector. Though tiny, this part is tasked to spray gasoline to the engine to improve its performance. But, just like any other mechanical part, the fuel injector can sometimes malfunction causing your auto to behave weirdly. Thankfully, the fuel injection system can be repaired quite easily by observing the signs of bad fuel injectors.

The fuel injector is among those components that are key to your engine’s performance. Located at the heart of your engine, this part picks a lot of physical abuse that exposes it to regular clogging and rapid wear. Failure to inspect it regularly can cause the engine to malfunction. So, in this guide, we’ll provide a quick overview of what a fuel injector is before summarizing at least seven common signs of a bad fuel injector.


What is Fuel Injector?


Although the fuel injection system boasts of being several decades old, there’s a greater chance most motorists are hearing about it for the first time. But, don’t you worry. The fuel injector system is a sophisticated system that consists of the fuel filter, the fuel injectors, and the fuel pump. This complex interconnection is usually located under the car’s hood.

Fuel injectors are basically solenoids or cylindrical coils that have atomizing nozzles on one end. In most modern vehicles, such as light trucks and cars, the engine system is designed with one fuel injector per cylinder. This means that if your auto’s engine has four cylinders, then you’ll expect to find four fuel injectors.


How Do Fuel Injectors Work?


Now, for older cars manufactured before the 1980s, the fuel injector was located in the engine’s head in the intake manifold. Its purpose was to spray gas on the upper or lower manifold to have it mixed with air before getting to the combustion chamber. With modern cars, the technology has completely changed where fuel injectors are now located on the engine’s cylinder heads.

This new technology, also known as a continuous injection, comprises of fuel injectors that spray fuel directly to the engine’s cylinders to improve combustion. To guarantee efficiency, the nozzles must be angled correctly and must spray gasoline with correct pressure and pattern.

To function optimally, these injectors don’t function by themselves but are rather controlled by an electrical control unit or rather the central computer. As the brain of your car, the ECU is usually the one that controls the pressure of fuel that’s sprayed on the engine cylinders.


Why Do Fuel Injectors Malfunction?


Now that you’re aware of how fuel injectors work, the next step is to discuss the major factors that cause them to malfunction. At a glance, fuel injectors may seem like little nozzles that spray gasoline to your engine’s cylinders.

However, if you dig deeper, you’ll realize that these components are precise instruments that function with minimal error. But, just like other mechanical parts, fuel injectors can sometimes malfunction due to one reason or the other. So, in this section, we’ll discuss three key factors that cause fuel injectors to malfunction.


  • Clogging:

One of the major culprits of a faulty fuel injector is debris clogging in the system. You see, your fuel injector is designed with tiny holes that allow gasoline to be sprayed in a fine cone-shaped mist.

Due to this reason, these holes can sometimes be susceptible to clogging if there are high amounts of sludge in your fuel. Using poor fuel quality that has excess debris and impurities can cause the fuel injectors to malfunction especially when these by-products clog the nozzles.

Heat soak is another phenomenon that can cause your engine’s fuel injectors to clog. This happens when fuel residues or additives begin to evaporate when the engine is off for too long.

Since there isn’t any flowing gasoline to flush them out, these residues can harden into clogging deposits that can clog the fuel injectors over time. Thankfully, most fuels have special detergents that get rid of such residues easily.


  • Injector Solenoid Failure:

The injector solenoid is a part of the fuel injector that uses an electromagnet mechanism to control the opening and closing of the nozzle.

But, just like other mechanical parts, the injector solenoid can sometimes malfunction due to several reasons. One of them is an electrical malfunction that forces the computer to send electrical power to the solenoid for a longer time causing it to break.

Another reason is when the field coils in the injector malfunction. Lastly, the bushings in the injector can wear out causing the plunger to cock sideways. This, as a result, can cause the nozzles to spray gas sideways.


  • Damaged Components:

The last major culprit of a damaged fuel injector is faulty internal components. This can be caused by leakages due to worn-out sealing rings, worn-out return spring, or damages to the pintle. In the case of the return spring, you’ll notice that your injector will work normally in low rpm but develop misfires at high rpm. In most cases, these components malfunction due to poor installation procedures or if your mechanic accidentally drops the injector damaging some parts severely.


7 Symptoms of Faulty Fuel Injector


A fuel injector is a crucial component that determines the overall performance of your car’s engine. Unlike the traditional carburetor, the fuel injector system offers a myriad of benefits to your car’s drivability one of which is increasing engine efficiency for a more improved fuel economy.

But, just like any other mechanical component, the fuel injector can sometimes malfunction. This can either affect the amount of gas being sprayed on the engine or affect the interval at which the nozzles are supposed the spray the gas. In either way, this section will discuss at least seven major symptoms that can signal a faulty fuel injector or injectors.


  • 1. Engine Light Turns On

One of the most obvious signs of a damaged fuel injector is when the “Check Engine” light suddenly illuminates. You see, one thing about modern vehicles is that they’re controlled by a central computer that sends signals whenever there’s a system malfunction.

Although the “Check Engine” light can signal a lot of issues with the engine, one of them is a faulty fuel injector. When the injector is damaged, it means it’s either delivering less fuel or excess fuel to the engine. In case of such a symptom, the best step is to tow your auto to the nearest repair shop to have it inspected.

During the inspection process, your mechanic is likely to use an OBD2 scanner to try and read the error codes from your car’s computer. This data is then translated to identify the exact problem. Once the problem is found, your mechanic will then determine the right course of action in terms of repair.


  • 2. Engine Stalling

Earlier on, we mentioned that the fuel injector is tasked to spray gas to the engine to maintain consistent performance. Now, imagine the fuel injector is clogged or damaged in some way. What will happen with the injector is that it will either spray excess fuel or insufficient fuel to the engine.

As a result, this inconsistent delivery of fuel can create a lean or rich fuel mixture that can either cause the engine to misfire or stall. In most cases, the engine’s RPM can decrease significantly causing the engine to idle or turn off in the middle of traffic. In severe cases, the car can vibrate or idle violently making it impossible to control.


  • 3. Engine Vibrating and Misfiring

Earlier on, we mentioned that one issue that can lead to a damaged fuel injector is the clogging of the nozzles. We also mentioned that the fuel injector is tasked to spray fine mists of fuel to the engine’s cylinder. Now, if the nozzles are blocked by impurities, then it means the injector will be unable to supply sufficient gas to the engine.

Failure to supply enough dose of fuel as demanded by the car’s ECU means that there will be an insufficient fuel-air mixture in the engine. This, as a result, will lead to detonation that will cause the engine to hiccup and vibrate.

In the case of turbocharged engines, the turbo boost mode will demand excess fuel be sprayed to the engine. If this doesn’t happen, the engine might struggle to cause a detonation. The engine is also likely to overheat leading to premature turbo failure.

Another symptom you’re likely to notice with your engine is misfiring. Again, this issue occurs when the engine is sprayed with insufficient fuel. The engine is also likely to overheat causing it to malfunction in some cases. You may even notice that your car is struggling to move even after you press the gas pedal.


  • 4. Fuel Leakage

Another major symptom of a faulty fuel injector is consistent fuel leakage in the engine bay. Fuel injectors have many plastic parts that can get damaged over time. These injectors are sealed with rubber seals which can also wear out over time. So, after a long time of withstanding heavy abuse, these parts can give up eventually causing gas to leak inside the engine or on the fuel rails.

When left unrepaired, these gas leakages can cause the fuel injectors to supply the engine with insufficient fuel. As a result, other signs such as the engine stalling, idling, and misfiring can be evidenced.


  • 5. Fuel Odor

This sign usually goes hand-in-hand with possible fuel leakage. To those that are very keen on odors, smelling anything unusual means that your car demands professional inspection. One of those odors is the smell of fresh gasoline whenever you start your auto. In most cases, smelling fresh gas points to three major culprits.

One of them is damaged fuel lines while the other is a damaged fuel injector. The last culprit is faulty sensors that might instruct the ECU to demand more gas to be sprayed to the engine. If the excess gas ends up leaking, then there’s a possibility of fuel odor when you start the engine.


  • 6. Engine Surge

There are times when the fuel injector may spray excess fuel into the engine. This can be due to a clogged or damaged fuel injector. If this happens, the fuel injector will create an imbalance in the fuel-air combustion ratio as there will be excess fuel being burned. This excess fuel can cause the engine’s RPM to increase noticeably even when the car is towing a constant load.

As a result, your car’s engine is likely to surge causing the acceleration to slow. Since there will be excess unburnt fuel, your car can release a lot of emissions to the environment which can be hazardous. Also, having a rich supply of fuel to the combustion system can harm the catalytic converter leading to hefty repair costs.


  • 7. Poor Fuel Economy

If your car’s fuel injector is faulty, then it will either supply excess or lean amounts of fuel to the engine. If it supplies less fuel, then the car’s ECU will drain the fuel tank to supply more fuel to the engine. If there are leakages, then most of the fuel will end up being wasted. As a result, your car’s fuel demands will increase significantly leading to poor fuel economy.



According to most automotive experts, the fuel injector is a component that can last for a very long time. In most cases, this component can last for up to 100,000 miles but depending on two conditions. One of those is the quality of fuel you use while the other is the frequency of replacing the fuel filter.

But, just like any other mechanical component, the fuel injector can also wear out due to old age, clogging, solenoid failure, or damages to its internal components. If this happens, any of the seven signs we’ve discussed in this guide can be evidenced.

So, in case you detect any of the above symptoms, it’s always recommended that you tow your auto to the nearest repair shop. This way, your mechanic will diagnose your vehicle to detect/fix the problem early enough before it gets any worse.

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