Has Mercedes Always Been This Bad?

That is true Graham the modern truck is a different animal to what many of us were used to. Its not electrics its electronics, in other words everything is operated by ECU’s (maybe up to half a dozen or more spread around the chassis) which also means a computer is needed to look for and trace, hopefully the faults that come up, I say hope fully because as your Merc Technicians will have found it may only tell them the engine has an injector fault, not which one so there is little that can be done but replace them all. Due to common rail systems now its not possible to carry out the sort of manual diagnostics we could do previously like disconnecting separate injectors to trace the dodgy one. The fuel pressures used in these systems are extremely high and dangerous and as you say sometimes a fault comes up for no reason and cannot be traced sometimes it may even mean changing different components to solve it, not very economical. As for Dealerships nearly all have suffered in the last ten or so years from struggling to find Fitters of a good standard and many employ foreign workers, not that they are any less capable but there is sometimes the language problem. Fuel filters as you mentioned do indeed require more regular changing in these systems, on the Volvo Fire Appliances I worked on before retirement we changed them every six months and on Annual service along with the other oils and filters. These filters have a hand operated primer and have to be pumped up 250 times to fill the housing before the filter itself is placed in and secured, many of the lads had problems re-starting these vehicles until we sussed the right way, a real pain in the ■■■■. Just a brief explanation of how things are different hope it helped. Franky.