How to Clean Dirty Diesel Fuel Injectors – Beginner’s Guide

Clogged and dirty diesel injectors can lead to many common problems. Find out if your car or truck needs its injector cleaning, and how to save thousands by doing it yourself.

Noticed a lack of power in your diesel lately? Or plumes of smoke emitted from the rear of your car or truck? There are a number of reasons as to why this could be, but one primary culprit could be dirty or clogged injectors.

Unlike petrol engines, diesel injectors operate at a very high pressure. Because of this, injector cleaning is commonly overlooked. But clearing-out your diesel injectors can be as simple as using an additive at your next fill-up.

Ensuring your diesel engine’s injectors are clean means that their spray patterns are uniform (as intended), and blockages absent. This will restore power, economy and smoothness to any diesel engine. By cleaning your diesel injectors, you could find yourself saving thousands of dollars in both labor costs and the value that you may have shelled out on new injectors.

We’ve listed two methods below. The first requires little-to-no prior experience under the hood, while the second is for those more confident in their mechanical abilities. Either way, you can ensure your engine is running at optimum with a few basic tools and a little patience. Read on, to find out more.

Why Do Injectors Need Cleaning?

Diesel injectors are what spray fuel in to the engine cylinder just before combustion. But combustion often leads to carbon deposits building up over time. If you've ever seen soot in your tailpipe, this is one example of carbon build-up

Carbon build-up within your engine, and particularly on the injectors, may lead to the injector’s spray pattern becoming blocked and irregular. This can reduce power, harm fuel economy, lead to premature knocking under load, and reduce your engine’s smooth running—even at idle.

The Straightforward Way: Additives

By far the easiest way to go about cleaning your injectors on a diesel vehicle is by adding some form of cleaning additive to your diesel car or truck.

Two popular brands for this are Seafoam and Liqui Moly. The methods in doing so will vary between manufacturers, but as these two are the most popular, we’ll examine what you can expect to do with each.


Seafoam can be added according to the recommended ratio of diesel in your car or truck’s tank, but about 20 oz. to 10 gallons should suffice. It is then recommended that you change the fuel filter, and fill up or soak the filter (depending on if it’s a screw-in or lift-off type) with the seafoam additive. Once the filter is replaced, run the engine for about two minutes, before shutting off for a further 15 minutes. This is to use up the seafoam that has been added to the filter, and is the main process of clearing out whatever gunk that may have accumulated. After waiting 15-20 minutes you can run the engine as normal.

Liqui Moly Diesel Purge

Liqui Moly’s “Diesel Purge” is similar, but instead of adding it to your tank, you should use it straight from the can. This can be done by disconnecting and joining the feed and return lines before disconnecting and inserting the fuel intake and return lines into the can of Diesel Purge.

Top tip:

You must only run the vehicle before the Diesel Purge additive us used up, as running it longer will cause air to be sucked into the engine.

When changing the fuel filter, you can soak it in the Diesel Purge solution before cranking.

The Thorough Method

This one’s a bit more advanced, and requires some basic tools, and the confidence to work under the hood of your own vehicle. But it’s a handy procedure that eliminate the need to replace badly-fouled injectors — potentially saving you thousands in the process!

Step one is to remove your diesel injectors. Each engine will have a different procedure, so it’s recommended that you follow the manufacturer’s instructions.

Once removed from the engine you can proceed to disassemble the injectors. Be gentle with the injectors at all times, and look for evidence of carbon deposits at all stages. Using a steel brush and carburetor cleaning solution, remove any traces of carbon.

To test if the injector is working properly, remove the needle from the injector carefully (you may need the assistance of a magnetic tool for this). Then spray carb cleaner (with a pipe-nozzle) where the needle was housed. From the tip, you should be able to see the injector’s individual spray pattern. This will help determine whether there are any carbon blockages in your diesel injector.

If you find that the spray pattern is weak, or has blockages, it is recommended that you use either compressed air or a very fine wire brush to clean the tip of the injector nozzle.

After reassembly it is recommended that you change your fuel filter to prevent further blockages.

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