Volkswagen EA188 (1.9/2.0 TDI PD)

The unit-injector diesel family — Pumpe Düse, PD — that carried the Volkswagen Group between the rotary-pump TDIs of the nineties and the common-rail EA189 that replaced it. Built as a 1.9 litre eight-valve and a 2.0 litre in both eight- and sixteen-valve forms, so displacement and valve count are properties of the variant rather than of the family, and a 1.9 ASZ and a 2.0 BKD share a fuelling principle rather than a design.

Volkswagen applies the EA188 designation more widely than this page does. The three-cylinder 1.2 PD of the Lupo 3L carries it too, as do larger unit-injector units. This node is the four-cylinder 1.9 and 2.0, which is where the fleet and the failure modes are.

Everything diagnostically distinctive about these engines follows from having no high-pressure rail. Each injector is its own pump, driven by an extra lobe on the camshaft, so the camshaft does the pumping work that a separate pump does elsewhere. The consequences are specific and they are what an owner meets:

• Camshaft and hydraulic lifter wear is the signature failure, and oil specification is not a recommendation on this engine — the cam is carrying injection loads. A neglected or wrong-specification oil history is the first thing to establish, ahead of any scan.
• A rising oil level means fuel, not overfilling. Unit injectors seal into the head with a clamp and an O-ring, and a loosened or failed seal puts diesel into the sump. Treat an oil level above full as a fuelling fault to be found, never as somebody's mistake with the dipstick.
• The tandem pump — the combined vacuum and fuel lift pump on the end of the head — leaks, and it leaks onto and into things that matter.
• On the 2.0, the oil pump drive is the failure that ends the engine. The hexagonal drive between the balance-shaft module and the pump rounds off, oil pressure disappears without much warning, and the damage is total.
• Variable turbine geometry sticking from soot, giving overboost or underboost complaints that come and go with load.

Injectors themselves are a wear item with a life measured in the low hundreds of thousands of kilometres and a replacement cost that often decides the car's future. On later examples the particulate filter and EGR cooler join the list, with short-journey use the common thread — the same question worth asking here as on any modern diesel.