Mercedes W204 W221 Fuel Rail Left N/S High Pressure Injection OM642 A6420703395

The Mercedes W204 OM642 Fuel Rail is a precise component of the diesel engine's fuel system, responsible for stable fuel distribution to the injectors. The offered unit is a used part, allowing for an economical yet technically sound repair of the common rail system in Mercedes vehicles with the OM642 engine.

Specifications and technical data

• SKU: A6420703395
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A6420703395
• Substitutable numbers: A6420703395, A 642 070 33 95
• Location on the vehicle: Left
• Fuel type: Diesel
• Category: Fuel Injectors

Technical Characteristics of the Mercedes W204 OM642 Fuel Rail

The fuel rail for the OM642 diesel engine operates within a high-pressure system, ensuring uniform supply to all cylinders. A correctly selected fuel rail stabilizes fuel pressure, which translates to:

• precise diesel fuel metering to the injectors across the entire load range,
• efficient common rail system operation during cold and warm starts,
• reduction of engine vibrations and rough running resulting from fuel pressure fluctuations.

The component's placement on the left side of the engine bay facilitates service access and allows for relatively quick removal and installation in workshop conditions.

Purpose and Application in the Diesel Injection System

The fuel rail in the "Injector Nozzles" category works directly with the injectors and the high-pressure pump in a diesel engine. Its function is to:

• store fuel under high pressure and stabilize it before delivery to the injectors,
• maintain uniform pressure in all supply channels,
• cooperate with sensors and the engine control unit to correct fuel dosage.

A properly functioning fuel rail directly impacts the OM642 unit's running smoothness, exhaust emissions, and fuel consumption. In case of injection system problems – such as difficult starting, power loss, or excessive smoke – checking the fuel rail and injectors is one of the key diagnostic steps.

Benefits of Using an Original Mercedes Fuel Rail

Choosing a genuine Mercedes fuel rail from a dismantled vehicle is a solution that combines correct compatibility with a reasonable repair cost. The main advantages of this approach include:

• factory fit for the OM642 engine – no issues with geometry, mountings, or connections,
• maintaining common rail system parameters as per manufacturer specifications,
• direct replacement of a damaged fuel rail without the need for fuel system modifications.

Using components that are structurally consistent with the original system helps reduce the risk of leaks, ECU errors, and accelerated injector wear.

Condition, Installation, and Service Recommendations

The offered Mercedes W204 OM642 fuel rail is a used part intended for reinstallation after standard workshop verification. Before installation, it is recommended to:

• check the fuel system for leaks after installing the fuel rail,
• inspect the condition of the diesel injectors for proper atomization and sealing,
• perform a computer diagnostic scan to verify the pressure in the common rail.

To better understand the symptoms of injector and related system component failures, it is advisable to read the article describing diesel injector faults, their symptoms, and the consequences of neglect. This will help you more accurately assess when fuel rail replacement is justified.

Mercedes Injector Nozzles – Part Selection and Technical Support

If you also need other components from the Mercedes injector nozzles category, check out our dedicated offer: Mercedes injector nozzles. Focusing on one specific category makes it easier to select compatible components for the diesel engine's fuel system and maintain the consistency of the entire system.