OM606 - return line size
 

Hi all,

Quick question on this, I need to figure out which line is the return line from the pump to the tank, there are 2 hard lines, one is 10mm OD and the other is 8mm OD.

I am guessing the 10mm OD line is the feed with the 8mm OD line being the return?

I think the return line is nearest the sill, if you're talking about under the car.

10mm is feed in.
This may interest you ,
Apparent Air in fuel system, Mercedes-Benz OM.605/6 W210/W124 and 'G' Wagen

Thanks for that I will have a read, will also double check that they are the fuel hard lines coming into the engine bay by getting under the car in the next few days. I remember reading about the badly designed and badly implemented fuel system causing bubbles in the lines.