How to Clean Diesel Injectors Without Removing Them?

how to clean diesel injectors without removing them

Carbon deposits build up in the diesel fuel injectors over a long period of usage. So they should be cleaned once a car reaches 30,000 miles.

Neglect can cause many adverse effects, such as more fuel consumption, bad mileage, power decline, etc. It’s advisable to avail of a professional fuel injector cleaning service, where they’ll thoroughly clean the fuel injectors by removing them from the car and reinstalling them.

But if you’d rather DIY to spend less, you can safely clean fuel injectors without removal. Read on to be guided on how to clean diesel injectors without removing them.

Ways to Clean Diesel Injectors Without Removing Them


For this task, you only need to prepare a compatible fuel injector cleaning kit for your car. This convenient tool kit usually consists of the following:

  • A hose connecting to the fuel rail’s output hose
  • A fuel injector cleaner – the cleaning solution is specially formulated to eliminate deposits in clogged fuel injectors and help prevent build-up in them.

Note: It’s highly recommended to get the cleaner with Polyetheramine (PEA) to help dissolve hard deposits.

Make sure to get one suitable for a diesel engine or the make and model of your car. Ensure you get the appropriate kit by checking the details on the packaging and manuals or looking up product descriptions online.

Step 1: Uncover the fuel tank


There will be greater pressure in the fuel system than there usually is when you clean fuel injectors with a cleaning kit, as the cleaning solution would be applied with air pressure.

So for safety purposes, you must uncover the fuel tank to prevent combustion from excessive pressure.

  • Open the hatch that covers the fuel cap.
  • Uncap the fuel tank.
  • Leave the hatch open.

Step 2: Unplug the fuel pump relay from the fuse box


It’s also necessary to unplug the fuel pump relay from the fuse box to prevent the fuel pump from propelling fuel to the engine during fuel injector cleaning.

Usually, the fuse box is concealed with a plastic cover under the car’s hood.

There’s also usually a diagram on the backside of the fuse box’s plastic cover showing the different locations of its contents. See in the diagram where the fuel pump relay is located in the fuse box.

If the fuse box doesn’t have a diagram, refer to the car owner’s manual.

  • Pull the fuel pump relay out. Some needle-nose pliers may help to remove it.
  • Ensure the fuel pump is deactivated by attempting to start the car engine. It shouldn’t start.

Step 3: Make sure to turn off the engine


You can be shocked if you clean a dirty fuel injector with the engine on.

  • To work safely, make sure that you turn the engine off.
  • And take your car keys out of the ignition to ensure that the battery won’t power the engine.

Step 4: Find the fuel rail and disconnect it


The fuel rail, which delivers the fuel to the fuel injectors, has to be disconnected from its output hose. So the fuel injector cleaning kit can be connected to the output hose.

Fuel rail placement varies among cars, so check the car owner’s manual to know exactly where the fuel rail is in your car.

Once the fuel rail has been spotted, carefully disconnect it to not damage it or cause fuel leakage.

How to disconnect it also varies. Usually, it can be disconnected by:

  • Pressing down clips
  • Loosening clamps and unscrewing them with a screwdriver
  • Loosening a bolt and a gas tank lead pipe

Step 5: If your car has a fuel regulator pressure line, disconnect it


Some cars have a fuel regulator pressure line. You have to check whether your car has one.

You can see in the car owner’s manual whether there’s a fuel regulator pressure line in your car or not.

If your car does have a fuel regulator pressure line, also see in the manual where it is, which is usually near the fuel injectors.

Once you’ve found the fuel regulator pressure line, you must also disconnect the pressure regulator by gently pulling it off the vacuum line.

Step 6: Fill up the cleaning kit’s canister with the cleaning solution


With the fuel rail outlet hose all set for the cleaning kit installation, it’s now time to prepare the cleaning kit.

  • First, uncap the cleaning kit’s canister.
  • Pour the fuel injector cleaning solution into the canister all the way to the brim.
  • Close the cap tightly to prevent air pressure leakage that can cause the pressure to drop.

Step 7: Attach the cleaning kit to the hood


The fuel injector cleaning kit must be hung on the car’s hood for you to easily monitor the kit and the engine.

Fuel injector cleaning kits usually come with a hook. Use the hook of your kit to place it on the hood.

Step 8: Connect the cleaning kit to the fuel rail’s output hose


Fuel injector cleaning kits usually come with various connectors to allow the use of any car.

  • Choose the appropriate connector size for attaching the cleaning kit to the fuel rail’s output hose.
  • With the best-fitting connector, attach the pipe of the cleaning kit to the fuel rail’s output hose.

Step 9: Connect the air compressor to the cleaning kit


You need to apply air pressure on the fuel injector cleaning solution using an air compressor to release it into the fuel injectors.

  • Power on your air compressor.
  • Connect it to the fuel injector cleaning kit’s air inlet pipe.
  • Set the air pressure to about 40 to 50 PSI.
  • Open the valve located at the bottom of the cleaning kit’s canister.

Step 10: Run the engine


You need to run the engine to make the cleaning solution travel through the fuel system and clean blocked diesel injector. But don’t drive and just let the engine run until it stops.

  • Run the engine to allow the fuel system to use up all the cleaning solutions. This usually takes about 15 minutes.
  • In this step, the engine would run on the fuel from the cleaning kit. Once all of the solution is consumed and ran out, the engine will stop, and the fuel injectors are finally clean.

Step 11: Make necessary deactivations, disconnections, and reconnections


After the fuel injectors have been cleaned, you need to put things back in order. Just be careful not to get burned by the engine when disconnecting and reconnecting components.

  • Turn off the engine and let it cool first before touching any components.
  • Close the valve at the bottom of the cleaning kit’s canister.
  • Turn off and disconnect the air compressor.
  • Press on the pressure-releasing valve on the canister’s cap.
  • Disconnect the cleaning kit.
  • Reconnect the:
    • Fuel pump relay in the fuse box
    • Fuel rail to the fuel rail’s output hose
    • Fuel pressure regulator to the vacuum line
  • Put back the fuel tank cap and hatch.

Step 12: Run the engine to double-check


Finally, you need to make sure that the car is running smoothly and that it has no problems, such as leaks, abnormal noises, and smoke.

  • Start your car. Pay attention to the sound it makes. It should sound as it normally does and not make out-of-the-ordinary noises.
  • Do a little test drive to see if it’s in good working condition.

If there are any leaks, they may be caused by damaged o-rings or fuel injectors. They would have to be replaced.

If odd noises and smoke are emitted by the engine, you may have another problem in your car. So have it inspected by a mechanic.


Cleaning diesel fuel injectors is one of the important car maintenance practices to prevent problems in the engine and keep it in good working condition.

By using a fuel injector cleaning kit and an air compressor and carefully following these steps on how to clean diesel injectors without removing them, car owners, too, can safely clean their fuel injectors by themselves at home.

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