MajorCommonEngine

Mercedes-Benz C-Class: Delphi piezo injector failure (2.1 OM651 diesel, 220 and 250 CDI, 2009-2012)

Delphi piezo injector failure (2.1 OM651 diesel, 220 and 250 CDI, 2009-2012) is a common engine fault on the Mercedes-Benz C-Class on the 2009–2012 cars, and we rate it major. Putting it right costs $1,500 to $5,000 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 45 documented faults on the Mercedes-Benz C-Class.

Vehicle: Mercedes-Benz C-Class
Engine: 2.1L
Years: 2009–2012
Fuel: diesel
System: Engine

This page covers the Mercedes-Benz C-Class as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Mercedes-Benz C-Class faults45 documented faults on this model

What you are looking at

What goes wrong

Piezo injector failure is a known issue on the 2.1 OM651 twin turbo diesel built until about mid 2012, as fitted to the W204 C 220 CDI and C 250 CDI BlueEfficiency. The Delphi piezo injectors can fail, generally beyond 50,000 km, bringing on the engine warning light, limp mode and rough running. Mercedes-Benz first fitted revised piezo injectors and then ran a customer service action that changed the car to solenoid injectors with a new engine ECU and fuel return lines. Ask whether that service action was done, because a car still on the original injectors can need several injectors.

What you would notice

Engine warning light
Limp mode with reduced power
Rough or uneven idle
Hard starting or misfire feel

How to check it

Where to look. Engine bay, top of the engine under the cover, fuel injectors

Start the engine from cold and listen for rough, uneven running or misfire; check the dashboard for the engine warning light; test drive and feel for flat spots or limp mode under load.
Ask for records of injector replacement or the Mercedes injector service action (solenoid injector conversion).
If a workshop inspection is possible: have the fault memory and injector correction values read with a diagnostic tool, and check the injector part numbers to see whether piezo or solenoid injectors are fitted.

Parts involved: Fuel injector.

What it costs to put right

$1,500 to $5,000 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

“Has the injector service action (change to solenoid injectors) been done?”
“Have any injectors been replaced, and when?”
“Has the car ever gone into limp mode?”

Now check the Mercedes-Benz C-Class you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in the sources below. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them.

Mercedes-Benz C-Class buyer questions

Is delphi piezo injector failure (2.1 om651 diesel, 220 and 250 cdi, 2009-2012) serious on a Mercedes-Benz C-Class?

We rate it major and common on the Mercedes-Benz C-Class. Piezo injector failure is a known issue on the 2.1 OM651 twin turbo diesel built until about mid 2012, as fitted to the W204 C 220 CDI and C 250 CDI BlueEfficiency. The Delphi piezo injectors can fail, generally beyond 50,000 km, bringing on the engine warning light, limp mode and rough running. Mercedes-Benz first fitted revised piezo injectors and then ran a customer service action that changed the car to solenoid injectors with a new engine ECU and fuel return lines. Ask whether that service action was done, because a car still on the original injectors can need several injectors.

How much does it cost to fix on a Mercedes-Benz C-Class?

$1,500 to $5,000 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Mercedes-Benz C-Class years are affected?

Our research records this fault on the 2009–2012 Mercedes-Benz C-Class. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Start the engine from cold and listen for rough, uneven running or misfire; check the dashboard for the engine warning light; test drive and feel for flat spots or limp mode under load. Ask for records of injector replacement or the Mercedes injector service action (solenoid injector conversion). If a workshop inspection is possible: have the fault memory and injector correction values read with a diagnostic tool, and check the injector part numbers to see whether piezo or solenoid injectors are fitted. Look here: Engine bay, top of the engine under the cover, fuel injectors