Skip to content

TDI Fuel Injection Cleaning with Diesel Purge

Liqui Moly Diesel PurgeDiesel Purge by Lubro-Moly is a highly efficient fuel injection cleaner for diesel engines. When used properly, it is far more effective than other products, which are typically dumped into the fuel tank, and therefore diluted by the time they reach the injection pump and injectors. We used A4 chassis TDI (ALH engine) 99.5-04 Jetta/Golf/New Beetle for this write-up.


The objective is to remove the fuel lines at the fuel filter, insert a pair of adapters into the fuel lines, and feed those lines into the can of Diesel Purge. After that, the car is started and runs off the can of DP until almost empty.


2004 and later TDIs have an in-tank pump to provide fuel from the tank to the engine. You must disconnect power to this pump by either removing the relay or the fuse for the pump before starting the procedure. If you do not the pump will flood your engine compartment with diesel fuel from the tank.


From start to finish, the process should take approximately 30 minutes, including run time.


1. Open the hood of the car, and locate the fuel filter, located behind the passenger side headlight.

TDI Fuel Injection Cleaning with Diesel Purge 01

2. Locate the two black rubber fuel lines that go to the injection pump. Using a pair of pliers or vice grips, squeeze and move the clamps back so that the lines can be carefully removed. You will need to move the clamps approximately 2 inches back on the line, so that they are no longer clamping the nipple on the fuel filter.

TDI Fuel Injection Cleaning with Diesel Purge 02

3. If the rubber lines do not want to move, even after moving the clamps back, use a special hose tool to remove the lines. If you do not have this tool, carefully nudge them forward with a flat blade screwdriver, being careful not to nick or cut the lines, or damage the plastic nipples on the fuel filter.

4. With the lines removed, insert one of the plastic fuel line adapters you received into each of the rubber lines.

5. Open the can of DP, being careful not to spill it. Place the two lines into the can, and put the can in a safe spot on the engine where it will not tip over. If you can have a helper hold the can, at least initially, that is ideal. Note that as you run off the can, the can will get HOT so make sure your helper is holding the can with a cloth or gloves. Ensure that the lines are at the bottom of the can, where they will not suck air as the can empties.

TDI Fuel Injection Cleaning with Diesel Purge 03

6. Go inside the car and start the engine. Let the engine idle for the next five minutes. After that, your goal is to run the engine through various engine speeds (RPMs). I like to run it for a few minutes at 1500rpm, then 2000rpm, and so on, going all the way up to around 3500rpm at constant throttle. I also let it idle down completely, then rev it back up to almost redline, then back down again. There is no right or wrong method here, simply vary the engine speeds and run until the can is almost empty (but NOT completely empty!).

7. Either your helper or you must keep an eye on the fuel level of the can, by peeking inside from the top. Since the can is made of metal, it can be hard to see, so some people like to first empty the can into a clear container, or bottle (such as a clean soda bottle). I find that I can tell pretty well when the can is empty, so I don’t find this extra step necessary, but it’s up to you. You should also make sure that the lines are always fully inserted into the can, almost touching the bottom.

8. When you’ve decided it’s time to stop, turn the engine off. Carefully pull the lines out of the can, and then remove the line adapters from each line. Careful, the can and remaining fuel will be hot.

9. You can now reinstall the rubber fuel lines back on the fuel filter, or go ahead and replace the filter, since you’ve done half of the labor already. If you do replace the fuel filter, you can pour the remainder of the DP in the can into the fuel filter, and prime the rest of the filter with diesel fuel, Stanadyne, or your favorite fuel additive.

10. Reinstall the lines onto the filter, make sure the filter bracket is secured (if you replaced the filter), and go start the engine. If the engine does not start immediately, it may take a couple of tries (if air is in the system). Crank for no longer than 5-8 seconds at a time.

11. When the engine is running, let it idle a while and then check for leaks. When you are satisfied that there are no leaks, go for a drive. You will notice that the engine is quieter, there is less smoke, and you may even notice more power!

12. You’re done!

Related Products

Lubro Moly Diesel Purge is on sale at our sponsor and TDI specialty shop,

Update: Lubro Moly is now offering a professional strength version of Diesel Purge called the “Pro-Line Diesel Injection Cleaner

Disclaimer: TDI Blog technical tips are only suggestions on how to perform a task. You are responsible for following all normal safety precautions and factory procedures as detailed in the official service manuals. We assume no liability for your ability to perform these tasks. If you do not feel you have the skills to perform this task, visit a qualified mechanic instead. TDI Blog tech tips are copyrighted and cannot be reproduced or redistributed without our express written permission.

YouTube Video

Posted in TDI Do It Yourself.

Tagged with , , , .

36 Responses

Stay in touch with the conversation, subscribe to the RSS feed for comments on this post.

  1. Corey says

    Be careful during the summer months – the fuel lines and can can get HOT!


  2. jm says

    I’m feeling pretty special after doing the diesel purge… the process was relatively painless and towards the end one of the lines started drawing some air so a good time to quit. Turns out one of the supplied lines failed… looks like the bottom 2-3 inches split open. Extra hose clamps to finish the job was key as someone already pointed out.

  3. Caleb T. says

    Does an 04′ V10 TDI have a fuel pump in the tank I need to disconnect power to? Thanks

    • Corey@IDParts says

      Yes, the V10 Touareg does have an in-tank electric pump.

      • Caleb T. says

        Thanks, I just looped the tank lines and ran dp into the fuel filter because injector hoses are at the very back of motor and hard to get to without taking apart the fuel filter assembly. Next time I will use 2 bottles as the V10 sucked up one bottle in less than 10 minutes. Was getting rough starts with lots of smoke, not anymore!

        • Corey@IDParts says

          Good thinking! The V10 probably uses a lot more fuel than I’m used to seeing on the 4-cylinders. Diesel Purge can work real magic sometimes, glad to hear it worked out.

  4. gry says

    Is it acceptable just to pour a can of this stuff into the fuel filter when changing it and then running the car at idle? Have a 2005 TDI Jetta Wagon (BEW) old style…… with 118,000 miles on it.

    • Dennis says

      you can, but it will get diluted very quickly as the fuel from the tank enters into the filter and will then lose it’s purpose, if you just want to use something to fill that filter when changing, it’s cheaper to get a diesel fuel additive like Power Service or Stanadyne. Diesel Purge is meant to be used exactly as described in this write up, not hard at all, looks harder than what it really is.

  5. Kosto says

    Hello, Can i use this metod on my mondeo 2005 tdci or its works only on tdi ? thanks

  6. Mike says

    Should I prime the intake line somehow? Wont there be a air for a bit before the diesel purge reaches the engine?

  7. Evan says

    Help! I have a 2004 Jetta TDI and I when I tried to do this Diesel Purge procedure last night, I discovered diesel fuel streaming out of my fuel filter. So, I guess that means I have an in-tank pump on my car? So I have two options: Search somewhere under the dash and find a pump fuse whose number I don’t know, and then somehow disable that fuse. OR loop the fuel delivery lines together. The latter sounds simpler to me. But what exactly does “loop the fuel delivery lines together” mean? What are the fuel delivery lines? Where are they? Please be as specific as you can. I need really basic instructions. Thanks for any and all help!

  8. Tyler says

    Here is a how to video I made for anyone who wants to see how the diesel purge is done

  9. john bross says

    I have a 2010 TDI, do I have to unhook the
    fuse for the rear fuel pump. Thanks, John

1 2

Continuing the Discussion

  1. Thoughts on Seafoam. linked to this post on May 26, 2010

    [...] looking to clean the fuel injection system I would recommend going with Lubru-Moly Diesel Purge: TDI Fuel Injection Cleaning with Diesel Purge | TDI Blog hth's gb __________________ WANT A TOYOTA DIESEL ENGINE? Join the Import Vehicle Owners [...]

  2. Do business in asia linked to this post on December 10, 2011

    Do business in asia…

    [...]TDI Fuel Injection Cleaning with Diesel Purge | TDI Blog[...]…

  3. Car Repair Prices: Fuel Injection Services, Are They Worth Itc linked to this post on March 1, 2012

    [...] – brake-o-rama.comMallory 4193FI Fuel Injection Pump ReviewsMore Ways to Check Fuel InjectorsBreathe Deep With Your Cabin Air FilterAuto Fuel Injection CleaningFuel Injection Cleaner – Suggestion For Conserving MoneyFuel InjectorsTDI Fuel Injection Cleaning with Diesel Purge [...]

  4. Cleaning Injectors... - MBClub UK - Bringing together Mercedes Enthusiasts linked to this post on March 9, 2012

    [...] engine directly.. Here is another link that has step-by-step pictures on how to do a diesel purge: TDI Fuel Injection Cleaning with Diesel Purge | TDI Blog very useful [...]

Some HTML is OK

or, reply to this post via trackback.