Mercedes W164 Fuel Line Diesel OM642 Fuel Feed Return Pipe Hose A6420707832

Mercedes W164 Fuel Line Diesel OM642 Fuel Feed Return Pipe Hose is an original fuel system component designed for Mercedes diesel engines from the OM642 family. This component from the Lines, hoses and pipes group is responsible for the safe return of fuel from the fuel rail and injectors to the tank, stabilizing the operation of the entire system. Thanks to its factory geometry and fitment for diesel units, it ensures predictable engine behavior and proper fuel circulation.

Specifications and technical data

• SKU: A6420707832
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A6420707832
• Substitutable numbers: A6420707832, A 642 070 78 32
• Fuel type: Diesel
• Category: Hoses, Lines & Pipes

Purpose and function in the fuel system

The fuel return line in the OM642 diesel engine is responsible for draining excess fuel from the injection system components back to the tank. Maintaining proper flow in the return circuit is crucial for:

• stabilizing pressure in the common rail system,
• reducing fuel overheating in the rail and injectors,
• ensuring smooth operation of the power unit across the full load range.

Selecting a line dedicated to a specific generation of diesel engine allows for maintaining compliance with factory flow characteristics and minimizes the risk of leaks.

Construction and fitment for the OM642 engine

The fuel return line used in the Mercedes W164 with the OM642 diesel engine has been designed as a component that works with the factory injection system. The properly selected inner diameter, shape, and placement of connections allow for:

• secure connection to the rail and injectors without the need for modifications,
• maintaining tightness under high operating pressure conditions,
• operation in temperature ranges typical for diesel engines.

The original geometry of the line reduces stress on the joints and supports long-term, repeatable operation of the fuel system.

Application in service practice

Replacing the fuel return line is recommended in case of symptoms such as fuel leaks, the smell of diesel in the engine compartment, problems with starting a warm engine, or unstable idle speed. Using a line dedicated to the OM642 unit in the W164 body allows you to:

• restore proper fuel circulation in the return circuit,
• reduce the risk of air entering the system,
• maintain engine performance parameters in accordance with the manufacturer's specifications.

The element from this group is particularly important in vehicles used intensively, where the fuel system operates under high load for extended periods.

Product characteristics and condition

The offered fuel return line is a dismantled part, which allows for a favorable cost-to-quality ratio while maintaining the original manufacturer's specifications. A used component of this type is a popular choice in professional workshops for diesel system repairs when priority is given to compliance with the factory design and fitment for a specific engine model.

For users looking for a reasonable service solution for a Mercedes W164 with an OM642 diesel unit, such a line is a practical choice, allowing for a technically correct repair without the need to use replacements with uncertain flow parameters.

Selection support and additional information

Before purchasing, it is worth verifying the compatibility of the line with the specific vehicle configuration, especially regarding the type of diesel engine and the version of the injection system. In case of doubt, it is helpful to compare the shape and arrangement of the connections with the part currently installed in the car.

If you are planning a comprehensive repair or upgrade of the engine area in your Mercedes and need other elements from the same group, such as feed lines, flexible fuel hoses, or rigid return pipes, check the available parts in the Mercedes lines, hoses and pipes category.

Additional tips on choosing used fuel system components and other subassemblies for popular car models can be found in our guide: The best used car parts – a guide to the most frequently chosen original parts.