Category Archives: Cars

Diesel Purge on Mercedes E300TD

Does your Mercedes diesel started to get noisy and sluggish? There is one cost effective option, that you can try.
It will prolong the life of your diesel and its fuel system. Making your life easier, by saving a good amount of money on injector-fuel pump repairs.

It is called a “diesel purge”. Diesel purge is not only a chemical product, it is also a procedure, that you must follow, to achieve the desired results. The product is no miracle oil, that you would dump like a fuel additive in to the fuel tank and expect wonders to happen. You would have to disconnect the fuel supply and return hoses from the tank and connect them to the purge bottle. This injector cleaner cleans carbon deposits of injectors. Lubes the internals of the fuel pump and injector needles.

For more details check out the video below, how a diesel purge is performed on a 1998 E300TD Mercedes. The video was taken before performing the actual system purge, to see if there will be some improvements in engine performance. Right now the car is running on regular diesel. Knocking sound was coming from the middle of the engine, and was going away with more revs. I suspect a dirty injector. Time for a diesel purge.

The chemical i used is a professional product called Wynns diesel purge. I have heard great responses about wynns line of products, so i wanted to test it out for myself.
If you are not familiar with the purge process, there are some preparation steps involved:
1. Find out where the fuel feed and return lines are in your car’s engine bay.
2. Buy a new fuel filter and necessary gaskets and rings, that come with it. You will replace the old fuel filter after the purge.
3. Buy a good 6 ft. or 2 meters of clear durable hose. This will be used as fuel lines, so you have to find out what diameter is needed in your particular case. Clear hoses give you great indication of air bubbles and overall dirt in the system.
4. Buy a simple inline diesel fuel filter. This will be hooked inline with your engines fuel feed.
5. Get a clear clean glass jar about 1 litre.
6. Get the actual diesel purge. You can use wynns or liqui moly or lubro moly, there all excellent products.
Do not buy “add to fuel” types, buy for professional use only.
7. Prepare your tools, get a cleaning rag.

Make two clear fuel lines from your hose, about 1 meter or 3 feet in length. You can always shorten later.
Cut one hose in half and connect your in line fuel filter in the middle.
Turn off the engine. Park your car. Wait a couple of minutes, for the fuel to return to the tank. Disconnect the fuel feed and return lines before the main fuel filter. Get ready for some minor fuel spillage.
Connect the hose with the filter to the fuel feed side of the engine. Take care, that the fuel flow direction of the filter must point to the engine side. This line will supply your engine with diesel purge from the glass jar. Connect the fuel return line of the engine to the jar. Secure the jar, secure the fuel lines. Fill up the jar with diesel cleaner. Start the car – check the setup for air bubbles and leaks.
On this Mercedes, the fuel feed is the bottom line and top for return:

I recommend using a glass bottle or jar, because the diesel purge will get hot after some time.
Let the car run on idle for about 5min, or longer, if the engine is cold. By now you will notice, how silent the engine purrs… Then gradually increase engine revolutions to 2500 rpm it should be enough. Do not “redline” it! Slowly increase for couple seconds and back off to idle for 10 seconds. Do this until you finished half of the bottle.
Turn of the engine. Let the cleaner soak in all the entire gunk for about 10 minutes. Restart the car. Again slowly increase engine revs and back off to idle. Do this until the cleaner is almost finished, this way you won’t get any air in the fuel system.
Reconnect the feed and return lines to the fuel tank. Change the fuel filter. You have successfuly performed a diesel engine purge. Now you will have a more responsive, economic, well maintained car.
Mercedes E300TD after the testing:

Conclusion:
Hard knocking noise on our Mercedes is now gone and the engine feels much smoother and quieter on regular diesel.
I never heard my car run so quiet when it was on purge, i wish i could run it all the time.

Notes:
To Mercedes owners. Replace the o-ring on the filter and on the nut, that holds the filter.