Fallo del inyector Mercedes OM654: síntomas y soluciones

A failing injector on the Mercedes OM654 2.0d usually shows up as rough idle, a diesel knocking sound, black or white smoke, rising oil level from fuel dilution, or the car dropping into limp mode. These symptoms overlap with other faults, so the safe move is to diagnose the specific cylinder before replacing anything.

The OM654 is the 2.0-litre four-cylinder diesel fitted to the C220d (W205), E220d (W213), GLC220d (X253) and Sprinter, among others. It is a strong engine, but its high-pressure common-rail injectors work under enormous stress, and when one starts to fail the whole engine feels it.

What are the symptoms of a failing OM654 injector?

A single weak or leaking injector rarely fails silently. Watch for these signs:

• Rough or lumpy idle that smooths out slightly once warm, often with a vibration you can feel through the cabin.
• Diesel knock or ticking that gets louder under light load — a stuck or over-delivering injector disturbs combustion timing.
• Black smoke (over-fuelling) or white/grey smoke (unburnt fuel from an injector that isn't atomising).
• Fuel in the oil — the dipstick level rises and the oil smells of diesel. A leaking injector can wash fuel past the rings into the sump.
• Limp mode / reduced power, often with the engine management light on and a stored fault code.
• Hard starting, especially when hot, if an injector is leaking down rail pressure.

Which fault codes point to an injector?

Generic diagnostic codes give you a direction, not a diagnosis. On any modern diesel you may see cylinder-specific injector circuit codes in the P0201–P0204 range (one per cylinder), and misfire codes in the P0300 series (P0300 random misfire, or P0301–P0304 for a named cylinder). These tell you where to look, but they can be triggered by wiring, compression or fuel-supply problems too — not only the injector itself. Always confirm with live data before condemning a part.

Why do OM654 injectors fail?

Common-rail injectors fail for a few well-understood reasons. Poor-quality or contaminated diesel accelerates wear on the fine internal parts. Water in the fuel causes corrosion. Long service intervals let the injector tip carbon up, disturbing the spray pattern. And simple age and mileage matter — these parts operate at very high pressure thousands of times a minute. Once the nozzle wears or a valve sticks, delivery becomes uneven between cylinders.

How do you diagnose it before replacing?

Don't guess. A proper diagnosis on the OM654 should include:

1. Read stored and live data with a diagnostic tool. Look at per-cylinder correction values and injector return quantities — an outlier cylinder is the prime suspect.
2. Compare cylinder contribution at idle. The ECU shows how hard each injector is working to keep the engine balanced.
3. Check the fuel return (back-leak) if your equipment supports it. An injector leaking excessively internally will show up here.
4. Rule out the cheap stuff — wiring, connectors and a blocked fuel filter can mimic injector faults.

If your diagnosis confirms a single failed injector, you don't necessarily need a full set. Replacing the faulty unit with a tested used OEM injector matched to your engine is a common, cost-effective repair.

What are your repair options?

You broadly have three routes: buy a brand-new Bosch injector (highest cost), have the original ultrasonically cleaned and flow-tested (works only if the nozzle isn't worn out), or fit a known-good used OEM injector with the correct part number. For the OM654, the injectors that fit are the A6540700300 / Bosch 0445118034 for C220d, E220d, GLC220d and Sprinter, the piezo A6540730087 / 0445118009, and the A6540700187 / 0445117048. Whichever route you choose, remember an OM654 injector carries a calibration code that must be written to the ECU — see our guide on injector coding (IMA) before you fit anything.

Buying used? Learn how to check a used injector before installing it so you fit something reliable. Every injector in our fuel-system category is graded honestly with defect photos, ships EU-wide from Bulgaria in 3–7 days, and carries a 14-day return.

FAQ

Can I drive with a failing OM654 injector?

Briefly and gently, yes, but you shouldn't. A leaking injector can dilute your oil with diesel or cause a misfire that damages the catalyst and DPF. Diagnose it promptly.

Do I have to replace all four injectors at once?

No. If diagnosis points to one faulty cylinder, you can replace that single injector, provided the replacement is the correct OEM part for your engine and is coded to the ECU.

Is fuel in the oil always an injector problem?

Not always, but a leaking injector is one of the most common causes on a common-rail diesel. Confirm with a per-cylinder back-leak test rather than assuming.