A6420700587 — Symptoms & Failure Modes
Common symptoms and verified failure modes of a failing Bosch A6420700587 (0445115027) Mercedes OM642 3.0 V6 CDI Piezo Injector.
Hard starting and poor cold running · high
Worn piezo injectors with high back-leakage drop cranking rail pressure.
Rough idle / misfire · high
An out-of-balance injector under/over-fuels a cylinder.
Black carbon ('black death') around an injector base · high
A failed seal lets combustion gas escape and carbonise around the injector bore.
Smoke, rough acceleration and loss of drivability · medium
Worn nozzle/needle degrades metering.
Increased fuel consumption · medium
Over-fuelling or leakage wastes fuel.
Audible leak/hiss near the injectors under load · medium
Combustion blow-by past a failed copper seal.