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How to Clean Fuel Injectors

Updated on August 16, 2009

Dirty Fuel Injectors

Most people don't think about the fuel injector in their car, but it is important that it is kept clean, but how does it get dirty? Well, gasoline vapor deposits are left in the fuel injector nozzles after the engine is shut down, and over time it just builds up, clogging the injectors.

Depending on the gasoline that you buy, you can purchase that which is already mixed with additives and detergents which help reduce clogging and dirtying the fuel injectors. Otherwise, you need to make sure that you periodically clean them every 25,000 to 30,000 miles in order to ensure top performance and emissions and overall fuel intake.

When to Clean Fuel Injectors

If you're not sure whether it's time to clean your fuel injectors, you can diagnose dirty fuel injectors by the following signs.

  • The vehicle hard starts
  • If you attempt to crank your engine and feel a hesitation when the engine is turning over
  • If it takes several attempts before the vehicle starts
  • Roughness when the car idles
  • Abnormal knocking sounds from the engine that may go away when the engine is at higher speeds
  • Increase in fuel consumption
  • Change in overall performance of the car
  • Hesitation when you step in the gas pedal when attempting to gradually increase speed

If you feel that your vehicle may be suffering from dirty fuel injectors, you'll find there are two different ways that you can clean your car fuel injectors- either keeping them in the car or taking them out. Generally, you can clean the injectors while leaving them in just fine. If you must remove them, you'll find that this is typically not going to be a do-it-yourself project.

Left side is dirty; Right side is clean
Left side is dirty; Right side is clean

Cleaning Fuel Injectors

If you're going to clean the fuel injectors, keeping themĀ in your car, you'll find it pretty simple, especially if you're going to clean the injectors within the vehicle.

  1. You want to either disable the fuel pump and plug the fuel return line or install a U-tube so the fuel will not return to the engine when it's started.
  2. Disconnect the pressure regulator.
  3. Connect the cleaning kit to the fuel port, but make sure that you remove the fuel cap from the gas tank to make sure that pressure doesn't build up inside the system. Cleaning kits can cause large bursts of pressure to the fuel system, so it's important to remove the gas cap.
  4. You want to open the valve until the fuel pressure matches what your owner's manual says is appropriate for your car.
  5. Turn on the ignition to the vehicle so that the pressurized solvent in the cleaning kit will run through the engine for five minutes.
  6. After shutting off the ignition, reset the fuel pump, replace the gas cap, and reconnect the pressure regulator.
  7. Start the engine and check the fuel injectors to make sure they are operating properly. In order to make sure that all is working, you can use an extra long screwdriver and listen for clicking sounds in a rapid sequence, which indicates that the injectors are working properly.

Clean Fuel Injectors by Removal

If you want to remove the fuel injectors in order to clean them, you'll find that this really isn't a do-it-yourself project. It can require special equipment and experience to do it properly.

A good mechanic may charge you $40 or more per injector to remove and clean it, which is much cheaper than spending over $4000 to do it yourself by removing the injectors after purchasing the proper equipment.

It is just a lot cheaper to clean the fuel injectors leaving them in the vehicle than removing them from the vehicle.

But, if you really want to remove the injectors, you will find that it is cheaper taking your vehicle to a mechanic to remove the injectors for cleaning than to have to replace the fuel injectors because they were so badly clogged and dirty that a good cleaning won't fix them.

A mechanic can test, observe, and compare the injectors when off the car, which is somethingĀ that you may not be qualified to do at home, especially if you end up needing to pinpoint the problems with an injector and if you end up needing to replace the fuel injectors.

Top image is correct;   Bottom image shows there's a problem
Top image is correct; Bottom image shows there's a problem

Other Tips to Cleaning Your Fuel Injectors

  • Cleaning solvents can be acidic, so make sure that you wear proper eye and skin protection.
  • The cleaning solutions can be flammable, so make sure that you are not near any flames or sparks.
  • Stronger cleaning products may eat through rubber and plastic components in the fuel pump, regulator, and fuel lines.
  • If the fuel injectors are badly clogged and dirty, the cleaning solution may not pass through properly in order to throroughly clean the injectors.
  • Consider checking your HC and CO levels when you clean the fuel injectors in order to make sure that they are responding properly to the cleaning solution after you've cleaned the fuel injectors.
  • After you've cleaned the injectors, you should notice 5-7% variation between the injectors, so if an injector is not passing as much liquid as it should, you should try more cleaning. If the injector still isn't responding properly, you should consider replacing the injector.
  • When testing the injectors, you want to see a cone-shaped mist spraying from the injector, if the spray pattern is of streams or unvaporized liquid, you'll need to replace the injector.
  • Be careful of what gasoline you use, as the cheaper gasoline is more likely to clog your fuel injectors than a more premium quality.


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    • profile image

      Ntanda Edward 

      6 years ago

      this has been so helpful, i have been increasing the Power adjustment because of a Clogged Fuel injector.

    • ScientificGear profile image


      8 years ago

      This is a very informative hub. May I add that one way to effectively clean fuel injectors is through ultrasonic cleaning. An ultrasonic cleaner is safe and easy to use, and cleans a wide range of materials in less time.

    • WholesaleParts profile image


      8 years ago from Rutherfordton, NC

      Excellent article! I am inclined to say this really isn't a do-it-yourself project unless you have some mechanical knowledge. I have had many individuals call me at my salvage yard needing injectors because they were cleaning them and some how damaged the injectors.

      My advice is to prevent the injector from being clogged. The best way to prevent injectors from getting clogged is to use premium grades of a good brand name of gasoline that contains sufficient detergent to prevent varnish buildup.

      I also suggest using a good name injector cleaner once a month. I use Lucas The Upper Cylinder Lubricant with Injector Cleaners and Fuel Conditioners. I use it once every 3-6 months. It is an injector cleaner and fuel conditioner. Many individuals are looking for the cheapest gasoline possible due to the economy. If you are using cheap gas I recommend buy a large bottle of Lucas and using around 3 ounces for every 10 gallons of fuel every other fill up. A personal note, I have never had my injectors cleaned, and I have over two hundred thousand miles on my car.

    • huss691981 profile image


      8 years ago from Momence Illinois

      Fuel injectors are one of the most overlooked parts on today's engines. thanks for the good hub. Mike

    • HarperSmith profile image


      8 years ago

      Good hub, most people don't do enough preventative maintenance on their cars. Thanks


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