Renault K9K

A 1,461 cc common-rail diesel with a cast-iron block, in production since 2001 and fitted to more separate marques than any other engine here — Renault, Dacia, Nissan, Infiniti, Suzuki and Mercedes-Benz, where it is designated OM607. A Mercedes A-Class and a Dacia Sandero can share this engine, which is exactly the situation a per-vehicle reference cannot describe.

The fuel system is where it fails, and the failure is self-propagating. Injector wear lets metal particles into the fuel, and the contaminated fuel then damages the high-pressure pump and the remaining injectors — so a single failed injector left in service turns into a whole-system replacement. When one injector fails, the question is how long it has been failing, not whether the others are fine.

The second theme is lubrication at high mileage: the oil pump chain and pickup, and consequent bearing wear, are documented weaknesses, and turbocharger failure often follows an oil-supply problem rather than causing one. Investigate oil pressure and the feed line before fitting a turbocharger to this engine, or the new one fails the same way.