Car Model Guide/ Issues/ Piezo injector failure (early OM651)

Piezo injector failure (early OM651)

Attaches to OM651 at engine level · Fuel · carried by 8 variants across 4 chassis

Overview

Piezo injector failure (early OM651) is a common fault recorded against OM651 at engine level, typically from 100–200k km. It shows up as hard starting, rattle at idle, smoke, poor running and injector codes; sometimes fuel dilution in the oil. Where it's documented, the repair runs €1,200–€2,400 (full set fitted and coded at a specialist, costs dated 2026-07), and it can be partly checked before you buy. 8 variants across 4 chassis in this database inherit it.

€1,200 – €2,400

full set fitted and coded at a specialist · costs dated 2026-07

Likelihoodcommon

Typical onset100–200k km

Detectablepartially

Walk awayno

Evidencedocumented

What happens

Symptom. Hard starting, rattle at idle, smoke, poor running and injector codes; sometimes fuel dilution in the oil.

Cause. First-generation piezo injectors fail and can leak into the cylinder. Later production moved to a revised solenoid injector.

Later parts. Revised injectors on later production

Sources. Mercedes technical documentation · specialist reports

How to check it

Cold start

Cold start and listen for an uneven rattle; scan for injector correction values, which a specialist can read and interpret. Ask which injectors are fitted. A receipt naming the revised part is worth real money on these cars.

You get one. If the engine is warm when you arrive, come back another day.

FuelcommonPartly detectableevidence: documented100–200k km

Every variant that carries this

Variant	Chassis	Body	Years	Risk	Good buy	Cost as % of good buy
C 220 CDI OM651	W204	sedan	2009–2014	R3	€5,700	32%
C 220 CDI OM651	S204	wagon	2009–2014	R3	€6,000	30%
E 220 CDI OM651	W212	sedan	2009–2016	R3	€6,300	29%
E 220 CDI OM651	S212	wagon	2009–2016	R3	€6,650	27%
E 200 CDI OM651	W212	sedan	2010–2016	R3	€5,500	33%
E 200 CDI OM651	S212	wagon	2010–2016	R3	€5,800	31%
E 250 CDI OM651	W212	sedan	2009–2016	R3	€7,300	25%
E 250 CDI OM651	S212	wagon	2009–2016	R3	€7,700	23%

The last column is the point. The same repair is an inconvenience on one variant and a reason to scrap the car on another. A failure costing a quarter of the vehicle's value changes the purchase decision regardless of how rare it is.