I cannot help you if you have bad mechanics giving you bad advice. Even with a used engine being swapped you may end up with the same problem.
Find an educated and experienced mechanic who knows how to work on MB diesels (the only unique thing in these is the injection pump and how its timed)
sir this is the main problem of Diesel engine car owners that mechs here no nothing about it and the owner of car cant tune it because it requires specialized equipment and workmanship here we lack of it. now if i look around on charade diesel engine now aproxx 99% of diesel charades were swapped with the petrol engine for the very same reason.
its partly the owners fault too. I was repairing diesel engines in Karachi and was usually meeting customers who wanted Gold at dirt prices. I showed them the door out.
e.g. head gasket replacement of toyota 1KZ-TE requires new head bolts otherwise Im not doing it. guess what they did - go to some shadetree guy who "double stacked" the washers and tightened the head down - Obviously the shade tree guy does not know what a TTY bolt actually is. They will also remove thermostat valve (yeh vilayatee ilaqa ka hai), fill with well water (coolent - kemikal hai, aur sab kemikal buray hotay hain) lock the fan clutch (aisa hee hona chahiye warna fan ka faida kya) - and send the owner on their merry way
The result was an engine that starts and sort of runs (drinks fuel) - but has a service life cut to 1/4 of its actual life and eventual other idiotic problems like worn cylinders etc.
the owner does not want quality work - they will never spend 25 paisa on a required service part but will spend 2500 Rs on polishing and shining because it impresses the neighbors.
