We’re now more than 20 years removed from the arrival of electronically controlled diesel engines, so why are mechanical diesel engines still part of the conversation? For one thing, mechanical diesels remain relevant because a solid majority of them are still ticking. For another, many OEM’s and remanufacturers continue to produce, repair or rebuild the mechanical mills of old. But exactly why do mechanical diesels continue to be so desirable? In a word, reliability. No matter how refined, clean-burning, and powerful new-age, electronically controlled diesel engines become, their added complexity, shorter injection and turbo system lifespans, and higher costs continue to keep their simpler, mechanical counterparts in high demand.

To be sure, there are undeniable performance advantages associated with electronically controlled diesel engines. But when it comes to million-mile durability, mechanical remains king. This time, we’re spotlighting why mechanical diesels are more reliable than their late-model electronic siblings. And because the internal hard parts are essentially the same between these two engine types, it means the pitfalls of an electronic engine often exist in the electronics themselves. Below, we’ll cover everything from common injector issues to VGT turbo failure, and even the crippling effect a faulty sensor can have on an electronically controlled engine.