How to Clean Fuel Injectors – An Easy to Follow Step by Step Guide

Knowing how to clean fuel injectors is worthwhile for a couple of reasons.

Staying on top of maintenance can extend their lifespan, and boosting engine performance is another factor to consider. Optimal function isn’t possible if the injectors are clogged or dirty.

One vital aspect of fuel injector maintenance is keeping them clean. Clearing out buildup could save you the high cost of replacement. If the unit gets clogged past a certain point, no product will be able to fix it.

You’d be surprised at how many adverse effects a dirty injector can have on your motor. If you’re still not eager to do the job, in the article below, you’ll learn what symptoms can manifest, and why you will want to avoid them.

mechanics hand holding fuel injectors above an engine bay

In this guide on how to clean fuel injectors, we share the steps you should follow to use either a full-blown fuel injector cleaning kit, or a simpler in-tank product.

If you’re somewhat car-savvy, you may want to attempt this project with a kit. The latter option is better suited to novices.

Skill Level: Beginner (in-tank solution) to intermediate (cleaning kit).

Time to Complete: 10 minutes (in-tank solution) to 30 minutes (cleaning kit).

Tools Needed:

  • Safety goggles, gloves and mask.
  • Flat-head screwdriver.
  • Rags.
  • In-tank cleaning solution or cleaning kit compatible with your make and model of car.
  • Air compressor.
  • Pressure gauge (if not included in the kit).
  • U-tube or fuel return line.

How Does a Fuel Injector Become Clogged?

These devices inject fuel for combustion to power your motor. They’re controlled either electronically or mechanically to deliver the fluid in a mist, known as atomizing.

The mist emerges through the tip of the injector or the nozzle. When the unit is working as it should, the atomized spray will combust instantly.

This video demonstrates how the entire delivery system works:

If the internal mechanisms or the nozzle get grubby enough, a clog can form. This can be as a result of one or more of the following:

Residue from Vaporized Fuel

Deposits from combustion build up inside the chamber and on nearby components. If a large enough quantity solidifies over the nozzle, a clog will form.

Contaminated Fuel

Contaminants can exist or build up in diesel or gasoline. For example, certain strains of fungi or bacteria can form, making the diesel go bad.

This can occur due to water in your tank or aging fluid. It’s less likely to happen, but you may have even filled up with a bad batch.

Aged gasoline can grow tarnished or thicken with gummy deposits. If it passes through your injection units in this condition, the liquid can jam them up.

Corrosion Inside the Fuel System

Corrosion in the tank or pump can travel. Flaking rust particles could get stuck or accumulate, resulting in a faulty injector, which can eventually lead to damage, leaks and a gas smell in your car.

Dirty Fuel Filter

The filter will not capture every last particle of debris. However, it can take a long time for enough sediment or grime to slip past and result in a blockage.

When the filtration material grows saturated, it will be difficult for fluid to pass through it. What little that does get through will likely be contaminated.

What Problems are Associated With Clogged Fuel Injectors?

There are more than enough potential complications to motivate you to get to work. A blocked unit means that fuel injection won’t be normal.

An excessively lean or rich mixture will influence performance in a bad way. The below symptoms are telltale signs:

Hard Starts

It may take several tries to start up your motor with grimy units. If the combustible liquid isn’t emerging from the nozzle in a fine spray, it won’t combust as easily.

Noise or Vibrations While Idling

Choppy idling, accompanied by strong vibrations is another warning sign. If the clog is severe, it might feel like an earthquake is hitting your vehicle.

Increased Emissions or Failed Emissions Test

Partial combustion or insufficiently atomized fluid can lead to a smoking exhaust. If you fail your emissions test, the culprit might turn out to be your injectors.

Engine Surging (Inconsistent Rpm)

Dirty units could provoke unstable RPMs at a stable load. The erratic fluid delivery can result in trouble accelerating or sudden surges at a steady speed.

Engine Misfires

Misfires are a typical indicator of problems in the fuel system or ignition. To some, the noise of an engine misfiring can be exciting, but it’s not something to take lightly.

Fouled Spark Plugs

Deposits on spark plugs can suggest the same issue in the combustion chamber and the surrounding areas. This is likely to include components like your injectors.

Abnormal Combustion (Knocking or Pinging)

Knocking coming from your engine isn’t the opening to a joke. It’s a grave indicator that abnormal combustion is taking place.

This is known as detonation. It can result in severe damage or even total engine failure.

Higher Gas Consumption

If you’ve noticed your fuel budget has spiked, clogged injectors could be the reason. All the additional stress on your engine means it’ll burn through fuel faster.

Engine Overheating

For the same reason we mentioned in the previous section, your motor may be prone to overheating. Surging, misfires and similar troubles translate to significant strain on the engine.

Check Engine Light

The dashboard check engine light will eventually light up if all these symptoms persist. In modern cars, it’s a far cry from the so-called “idiot lights” found in older models.

The onboard diagnostics system (OBD) will be able to identify any faults in your vehicle. With the help of an OBD-II scanner, you can find out if your injectors are jammed up.

Get Repairs Out of the Way Before Cleaning

You’ll have to address any problems that could have triggered clogging beforehand. Otherwise, all your efforts with a fuel injector cleaner will turn out to be pointless.

If the filter is due to be replaced, the same blockages will form again. Corrosion particles from the tank will circulate through the system and injectors again. As you can see, any necessary repairs must be addressed before anything else.

Types of Fuel Injector Cleaners

There are two types of cleaners you can pick from. The one that suits you will depend on your level of expertise and how much effort you want to put in.

Whichever you choose, it has to be suitable for your vehicle. Open up your owner’s manual, there may be recommended cleaning products.

Review the brand you’re considering carefully. Some are best for older vehicles, others work best for severely clogged injectors.

In-Tank Solutions

These are substances made to circulate through the fuel system by way of your tank. They contain detergent compounds to break down buildup and clear debris.

You can check out some of the top products available in this category via our guide to the best fuel injector cleaners.

Kits for Direct Application

Fuel injector cleaner kits include tools to run a detergent solution through the fuel system. You’ll need to have a good air compressor for your home garage to work one.

The solution is forced through your system at high pressure, cleansing as it circulates. Some brands come with a solution, with others you’ll have to buy it separately.

It’s preferable to have a moderate level of automotive know-how. We’re only suggesting this because you’ll be disconnecting and reconnecting the parts that circulate gas.

How to Clean Fuel Injectors – With an in-Tank Solution, or a Kit

Cleaning Fuel Injectors With an In Tank Solution

Note that this is a general guide that applies to most in-tank solutions but you should check and adhere to the instructions on the bottle you bought and use to clean your fuel injectors.

Step 1: Check That You Have Enough Gas

The product guidelines will advise how full your tank should be before you treat it.

Step 2: Pour Solution Into Your Tank

Open up your tank and pour the specified quantity of liquid in.

Step 3: Drive as Usual

Take your vehicle out for a spin to circulate the cleaner. It may need time to take effect.

If nothing happens, if you do not feel improvement in any ‘clogged fuel injector symptoms,’ then you might need to use a kit or take your car to a mechanic.

The injectors could be severely clogged and require a more professional, thorough intervention.

Cleaning Fuel Injectors With a Kit

These instructions should be suitable for the majority of kits on the market. Having said that, don’t dismiss the instructions that came with the kit.

If the procedure deviates from the below steps, follow the provided instructions fo the particular kit you have instead.

Step 1: Protect Yourself and Choose a Safe Work Area

Gasoline is not only flammable, but it can irritate your skin and respiratory tract. You need to take special care with your safety equipment and work area.

Gloves, a mask, and goggles are mandatory. Keep everything on until you’ve completed the treatment and closed the hood.

Work in a shady area, or indoors, to avoid working in direct sunlight.

Finally, It’s an obvious tip maybe, but bears mentioning: don’t smoke while you’re doing this.

Step 2: Engine Must Be Cool

Give your motor a minimum of 45 minutes to cool off if you’ve you been driving recently.

Step 3: Locate Your Fuel Injectors

They won’t be in the same place in every engine. Your owner’s manual will detail where you can find them which will be accurate unless you own a modified vehicle.

If you weren’t responsible for the modifications, you might want to ask your mechanic for help.

Step 4: Disconnect the Fuel Pump

The connection between the pump and the injectors must be cut temporarily. If you spot a clamp on the hose line, remove it with your flathead screwdriver.

If there’s a clip, pinch or push the tabs to release them. Carefully detach the fuel line and pull it off the pump. There may still be gasoline in it, so don’t swing it around.

Attach your U-tube or fuel return line to ensure that any fluid inside the pump will return to the tank.

Step 5: Disable the Fuel Pressure Regulator

There won’t be any need for this component during the treatment. Your air compressor will be providing the pressure. Disconnect the vacuum line and set it to the side.

Step 6: Try Your Ignition

With the pump disconnected, your engine won’t be able to start. Take the time to try your ignition, especially if you’re new to this.

If the motor turns over, something isn’t right. Double-check that you disconnected it properly.

Step 7: Open Gas Tank

Pop open the gas tank to avoid pressure build-up. This is essential, as you’ll be using an air compressor.

Step 8: Prepare and Connect Kit

Read the manual that came with your kit to know how it should be set up. You’ll be connecting it to the fuel port.

Prepare the detergent solution as instructed. You may have to dilute it before pouring it into the canister the kit came with.

Step 9: Attach Air Compressor Hose to Kit

Set your air compressor at the pressure required by the kit. Stick to the exact figure: too low and it won’t work; too high could result in damage.

If your kit didn’t come with a pressure gauge, attach it now. Switch on the air compressor to start the cleansing.

Step 10: Start Vehicle and Let the Cleaning Solution Flow

You can now switch on your ignition. The detergent will circulate through your injectors for roughly 5–10 minutes.

Once your engine shuts down, you’ll know there’s no more solution left. Turn off your air compressor and remove the key from the ignition after this happens.

Step 11: Remove Kit, Once Done

Detach the kit and put it aside. You may want to give it a rinse before packing it away.

Step 12: Reconnect Pump and Pressure Regulator; Close Tank

Reattach the vacuum line to the pressure regulator.

Reconnect your pump, making sure everything is reattached the right way.

If fuel spilled out anywhere in the engine bay, wipe it up with your rags. You may want to dampen them afterward to clear off any remaining residue.

Close up the tank, replacing the cap and shutting the lid. Shut the hood and breathe easy—you can now take off your safety equipment.

Step 13: Clear Error Codes if any Appear

In some vehicles, messing around with the pump can cause error codes to appear on your CPU. If you see any of these codes, clear them.

Step 14: Go for a Drive

Take your car out for a spin to see if there’s any improvement. Poor engine performance may mean your injectors were too clogged to salvage.

Odd noises or new issues could mean you didn’t connect your pressure regulator or pump correctly.

All Clean Now

We hope you’ve found our rundown of how to clean fuel injectors useful. It shouldn’t take more than half an hour of your time and can improve the unpleasant symptoms we covered.

If neither an in-tank solution nor a kit makes a difference, a visit to your mechanic is in order. The clogged devices may have to be professionally cleaned or replaced. You don’t want to continue driving around while they’re filthy, or you could damage engine components.

Do you have any questions you’d like answered? Please leave us a comment, and we’ll respond to your queries below.

Kyle Palmer

From childhood go karting and motocross, to collecting and obsessing over scalextric, matchbox and radio controlled cars, I've always had an obsession with cars. Learning through manuals, books, trial and error, and more knowledgeable family members, I've also enjoyed tinkering with the mechanics and electronics of any vehicles I've owned. Now, over 3 decades later, I've started this site as a place for me to share my knowledge, to teach others how to care for and maintain their vehicles themselves, at home, so they can get the most of their vehicles and save a pretty penny compared to always seeking out professional help.

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