Mercedes W639 Vito equipped with an OM646980 Strinter engine

[Sumoto]

My 2007 W639 Vito 111 CDI has begun experiencing fuel-related troubles. Exiting the conversation.
The background is as follows: after performing repairs on an injector blow-by and the hold-down bolt threads, the car began to leak gasoline from its leak-off system. I suspected that I had been excessively forceful with the press-down clips on the plastic pipe fittings attached to the spigot pipes emerging from the side of the injector.I conducted a leak-off test and discovered that three of the injectors were defective, exhibiting excessive fuel leakage. Consequently, I acquired a whole set of replacement injectors, Honda copper washers, and new stretch hold-down bolts, and replaced them together with a brand new leak-off pipe system.
after a run test drive i noticed it was leaking yet again but this time knowing full well the leak off was just a dribble and the leaking wouldnt start until at lease five mins of running ,i then purchased another pipe set believing it must of been a dud set i had previously got and fitted another new set ,another test run and another leak ensued so this time i thought it must be having trouble to leak back into the in-tank pumped supply line where it is plumbed into via an alloy y adapter ,having looked at it i considered it could either be a clogged filter (where the in tank pump brings the low pressure supply into) or maybe a locked up non return check valve which is in the new replaced leak off pipe so i checked the valve using air line and a peice of stiff wire all good replaced filter and test drive ,still leaking fuel out of the weakest point of the rubber leak off sections between the injectors , this tells me the pressure of the system where it is supposed to bleed into is far too high ?


I assume that the return line to the tank may be obstructed. Could it be a defective pressure regulator valve in the common rail? Are there any technicians available to assist me in resolving this issue? I am perplexed; the vehicle starts and operates flawlessly. Could it be experiencing excessive pressure owing to a malfunctioning pressure control system? How does it control the pressure returning to the tank following its effective transit through the common rail?

I am unable to locate anybody with the requisite experience and traditional diagnostic skills to identify this type of defect from the past.

[Sumoto]

There must be someone available who can assist.
Kindly or

Is this forum as inactive as it appears?

[Lemmand]

The forum is highly active. Do you believe that such a comment is more likely to elicit assistance?

[Sumoto]

I sincerely apologise if my post caused offence. Based on my experiences over the years, it appears that very few individuals are willing to contribute or assist others. When such assistance does occur, it is undoubtedly invaluable, yet it seems challenging to connect with someone who possesses the necessary knowledge.

[Lemmand]

This platform is free to use, and your post was made less than 24 hours ago. Individuals provide responses here at their convenience and leisure.

Increased activity on the forum would reveal that numerous users are consistently engaging with others and offering precise and prompt assistance on various concerns.


Your assertion that "few if any want to contribute or help" is intriguing, as a brief review of your posts reveals that they predominantly solicit assistance without any indication of your own contributions.

[Anabroo]

I found his post quite caustic.

[Videoman]

The fluid in the return line consists solely of that which is not utilised during injection, specifically referred to as leak-off.

The common rail maintains constant pressure, allowing the injector to utilise it as needed, and ideally, there would be no return flow. However, we should anticipate some.
It may be advisable to conduct an additional leak-off test to determine if any injector exhibits excessive leakage. In comparison to the others, it should serve as a reasonable demonstration, given its novelty.


Inserting the plastic leaks into the injector can be challenging; I encountered difficulties with the new 'O' rings being excessively thick. Have you possibly solved one?

[Squirrrel]

What is the pressure on the rail? Have you verified the reading?

Is the leak occurring at the T fitting or at the top of the injector?