A while ago, the ‘all-mighty’ carburetor distributed fuel to all cylinders in an engine no matter how many they were. The problem with such a setting was the carburetor didn’t have precise control over how much fuel went into each cylinder.
The best attempt to fixing this problem is the fuel injector. Fuel injectors can be mechanical or electrical. Either way, they give the engine better control than a carburetor.
Each cylinder in an engine has its injector to ensure precise control over when and how much fuel gets into the combustion chamber.
The result is more powerful, and fuel-efficient engines than a carburetor could ever achieve.
Just like the carburetor of the old, fuel injectors can get out of calibration over time. However, they are more resilient and will serve you for thousands of miles before they need replacement or servicing.
What Are Fuel Injectors
Fuel injectors are, in essence, electronic valve assemblies that can open and close repeatedly in quick succession. They have an outlet nozzle that atomizes whatever fuel they let through, creating a fine mist rather than dumping it in a steady stream.
How Do Fuel Injectors Work?
Even though fuel injectors sound simple, they have to react precisely to instructions from your car’s ECU. Here is how the entire process around fuel injector operation goes.
- The fuel pump pushes pressurized diesel or petrol through fuel lines to the fuel injectors
- The Engine Control Unit (ECU) uses sensors to determine when to fire the injectors and for how long to fire them
- When the ECU sends the voltage signal to the injectors to open, the already pressurized fuel is sprayed into the engine’s intake in the form of a fine mist
- The injector valve closes automatically and waits for the next fire signal from the ECU
Your injectors will fail if anything affects how they deliver fuel into the combustion chamber.
Symptoms of a Faulty Fuel Injector
The most common problems fuel injectors face is clogging from debris in the fuel. Sometimes, they might develop mechanical or electrical issues too.
Here are the top things that hint at faulty fuel injectors.
Misfires Causing Your Engine to Shake
Anything that affects air, fuel, and spark in your engine could lead to misfires. This means that a faulty fuel injector could cause your engine to misfire and shake violently.
A misfire is when one or more cylinders fail to ignite at the right time, making the engine lose power momentarily or get power in jerky bursts as other cylinders continue firing.
Fouled fuel injectors won’t introduce the right amount of fuel to the cylinders at the right time, meaning combustion won’t happen.
Note that other problems like a vacuum leak or fouled spark plugs can also cause misfires.
A Check Engine Light
Since multiple sensors closely monitor an engine’s combustion cycle, the ECU will quickly pick up and display any problems within the system.
The only problem is you might not get a direct error telling you that your fuel injectors are acting up. Instead, you might get error codes for:
- Injector circuit malfunction code that happens there’s a problem in the entire fuel injector circuit
- Engine running lean if the fuel injector is clogged or isn’t firing enough fuel in the correct spray formation
- If the damaged fuel injector causes a misfire, you will get a misfire on cylinder X error code
- Engine running too rich if the injector is stuck open or the atomizing nozzle isn’t spraying fuel in a mist
- Catalytic converter efficiency below threshold error if the fuel injectors are providing too much fuel leading to more emissions than the catalytic converter can handle
Since all these errors could mean something more, you might have to check other culprits for each error or bench test your fuel injectors to ensure they are not the problem before buying replacements.
Your Engine Idles Rough
Sometimes, your fuel injectors might not fail badly enough to cause misfires or any of the above error codes.
However, they might still not deliver a healthy dose of fuel as required by the ECU. This leads to a lean air to fuel mixture that won’t cause a misfire will make the engine produce less power than expected.
This weak performance will make the engine to idle rough but get slightly better as the RPM picks up. Moreover, the rough idle gets worse when you add some load to the engine while it’s still on idle – for instance, turning on the AC or slipping the car into gear (automatic transmission) with the foot still on the brake pedal.
Your Engine Stalls Often
In cases where too little fuel is getting to your engine, it fails to create enough power to sustain its motion.
Consequently, the ECU will either stop the engine or stall by itself since it doesn’t have enough power to keep rotating. The experience will be similar to what happens in a manual car when you let out the clutch too much without applying some throttle.
If your engine stalls and the injectors are the problems, chances are they are blocked, or there is a fuel leak at the point the injector connects to your fuel lines.
A Fuel Leak
Clogged fuel injectors add pressure to the fuel system since the fuel has nowhere to go. If this happens, fuel will start leaking at weak points – often the point where the injectors connect to fuel hoses.
At times, the drop will happen in the injector itself. Very old injectors could fail and start leaking fuel into the cylinders or out into the open.
If it is to open, you will see fuel on or around the fuel injectors.
You are Getting Worse Fuel Economy
A faulty fuel injector can affect your fuel economy readout in a couple of ways. First, it could throw your fuel economy meter off. The car will think it is burning more fuel than it’s doing. Here’s how this happens
- The ECU uses oxygen sensor readings to detect a lean running engine
- It requests more fuel from the injectors
- Since the injectors are faulty or clogged, they don’t deliver the extra fuel requested
- The ECU accounts for the extra fuel that didn’t get into the combustion chamber in the first place
While you will still have the fuel in your tank, you can’t really tell unless you manually check your driven miles against your reserves. You will think you’re getting worse mileage at a glance.
The other way bad fuel injectors give you lousy gas mileage is when they dump more fuel into the engine than they should. Your engine runs rich and burns more than it should.
A leak by the fuel injector or the point where it connects to the fuel lines will also waste fuel affecting your fuel economy.
Your Car Releases More Emissions and Fails Emissions Tests
When your fuel injector’s delivery is off, combustion won’t be as efficient as it should. This increases the production of harmful emissions from the combustion cycle.
An excellent way to know you are getting more emissions than is acceptable is getting the ‘catalytic converter below threshold’ error code P0420. While it could mean your catalytic converter is damaged, it could also mean your fuel injectors are running your engine on an unideal air-fuel mixture. Sometimes, you will get more smoke at the tailpipe due to the incomplete combustion.
Engine Knock
Engine knock happens when fuel in the combustion chambers doesn’t ignite in small regulated sections. Instead, it burns erratically or ignites all at once.
This could happen when the air to fuel mixture is not correct. The result is a noisy engine and erratic shaking or vibration. While lousy spark plugs, wrong fuel, and carbon deposits are the main culprits, fouled fuel injectors can also cause a knock.
How Do Fuel Injectors Get Damaged?
Even though there are different fuel injection technologies (depending on injector location) in the market, chances are your fuel injectors will fail in one of the following ways regardless of where they’re located.
An External or an Internal Leak
Fuel injectors connect to fuel lines using O-rings. Since these O-rings are rubber, they can get hard and brittle over time. If they do, they won’t create a perfect seal with the fuel lines. This could lead to an external leak.
Internal leaks can happen when the fuel injector’s body or nozzle cracks or disintegrates as it ages.
A Mechanical Failure
Since a fuel injector is a mechanical valve, it has a couple of moving parts. It opens and closes hundreds of times in quick succession, which means it can only work for so long.
While they have a very long lifespan, there comes a time when you have to replace them.
A Solenoid Failure
Your fuel injectors pull up the valve mechanism using a solenoid that creates a magnetic fuel to attract it when it receives current from the ECU.
If this solenoid is faulty, the injector won’t open as fast as it should. It doesn’t matter how good the other mechanical parts are. It won’t work.
It could also fail if the cables delivering the current or the ECU itself are faulty and the signal isn’t getting to the injectors.
Clogged and Dirty
Since injectors sit in a scorching place, any fuel residue on them when the engine shuts down evaporates, leaving behind some gunk.
The amount of dirt left depends on how clean your fuel is. Poor quality fuel will clog your injectors fast.
Even natural clean fuel leaves deposits. That is why many fuel distributors add cleaning agents to their fuel to get rid of this gunk and keep your injectors, cylinders, and other engine components as free of carbon and gunk buildup as possible.
Pro Tip: If you make many short trips, the cleaning agents in improved fuel might not have enough to clean up your car’s components (including injectors). Plan occasional highway road trips to clean up your vehicle.
Can I Replace Just One Fuel Injector?
Yes, you can change just one fuel injector if the others are okay. Swapping around your spark plugs, injector coils, and fuel injectors is an excellent way to troubleshooting single cylinder misfires.
Changing the injector in the misfiring cylinder will help you ascertain if the injector is the problem.
Can All 4 Injectors Go Bad at Once?
While this is rare, it isn’t unheard of. Injector failure tends to be isolated, especially if you take good care of them.
However, things could go very wrong if you fill up with contaminated fuel that clogs all your injectors at a go.
Can I Drive With a Bad Fuel Injector?
It depends on what symptoms you are experiencing. If the engine idles rough and you don’t have any other symptoms, you could possibly keep driving. You might not notice it as it starts unless you are very keen.
However, the problem is bound to keep getting worse as many symptoms like misfires, knock and error codes start showing up, the potential of harming your car or getting stranded on the freeway increase.
Can a Bad Fuel Injector Damage the engine?
When left for too long, bad fuel injectors can damage your engine. The failures could lead to a cascade that could even leave you with a blown motor.
For instance, if the injector sends in more fuel, it could lead to a rich air-fuel mixture that could cause knock, make you fail emission tests, or damage your catalytic converter.
Due to a clogged fuel injector, a lean mix could make your engine misfire or vibrate more damaging engine mounts. It could also render the car less potent than you think and dangerous to overtake in. Finally, lean engines run hotter, making them more susceptible to overheating and related problems like a blown head gasket.
Do Fuel Injector Cleaners Work?
Yes. Fuel injector cleaners work. They are good at getting rid of gunk and carbon buildup on your injectors. Just ensure that you use them right and mix them to the right amount of fuel.
While they start working, as soon as you put them into the tank, you’ll start seeing results after driving for around 100 to 300 miles.
Are they worth it? Yes, if you are unsure of your fuel quality. Most modern fuel distributors add some form of cleaning agents to their fuel. This means that most of the fuel you buy already has detergents that clean your injectors, combustion chamber, and even the catalytic converter.
This means that cleaner additives aren’t as necessary as before. However, using them to supplement what the engine already has could yield better results.
Just don’t expect magic. They might not get rid of years of caked gunk or fixed an already damaged injector. If your car is relatively new, you could create a schedule where you add cleaners now and then – especially before going on a long drive.