Mercedes W639 Fuel Tank Diesel Complete Fuel Tank Unit 75L A6394711401

Visual condition of the part

The product shows signs of use visible in the photos.

Mercedes W639 Fuel Tank Diesel Complete Fuel Tank Unit is a complete solution for the fuel supply system in diesel engines, designed for the W639 series models. This component combines the functions of fuel storage and system supply, ensuring stable operation of the power unit and proper diesel fuel circulation. By maintaining factory geometry and mounting points, it serves as a practical base for professional fuel system repair in Mercedes vehicles.

Specifications and technical data

• SKU: A6394711401-1
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A6394711401
• Substitutable numbers: A6394711401, A 639 471 14 01, A6394701694, A 639 470 16 94, A6394701494, A 639 470 14 94, BG
• Fuel type: Diesel
• Category: Fuel Tanks & Filler Necks

Purpose and function in the fuel system

The presented tank integrated with a pump is a component from the Fuel tanks and filler pipes group, responsible for the safe storage of diesel fuel and its delivery to other system components. The design, adapted for diesel engines, enables proper venting, separation of initial contaminants, and stable supply under various engine load conditions.

This type of solution is particularly important in commercial and delivery vehicles, where the fuel system operates across a wide range of temperatures and loads. Using a dedicated tank with a pump helps reduce the risk of fuel supply interruptions, starting problems, and power drops resulting from unstable feed pressure.

Compatibility and part identification

The component has been designed specifically for Mercedes vehicles from the W639 family, which translates into a proper fit for factory mounting points, line routing, and body geometry. As a result, installation is straightforward, without the need for structural modifications or fuel system adaptations.

To facilitate selection for a specific engine version and model year, the part has an assigned OEM number and a set of interchangeable numbers, allowing for precise verification of compatibility with the vehicle via manufacturer catalogs or the VIN. This approach minimizes the risk of purchasing an incorrect component and facilitates integration with the existing fuel system.

Technical characteristics of the Diesel system

A Diesel supply system requires a properly designed fuel tank that ensures stable delivery of diesel fuel to the high-pressure pump and injectors. In the case of this solution, the key factors are:

• maintaining the proper fuel level in the pump's working chamber,
• limiting fuel aeration when the tank level is low,
• ensuring proper return flow and fuel circulation,
• resistance to typical contaminants found in diesel fuel.

Combining the tank and pump into one unit facilitates diagnostics and service, and also allows for consistent management of fuel flow parameters throughout the entire system.

Condition, application, and installation recommendations

The offered component is in used condition, meaning it has been removed from a vehicle and is intended for further use after proper installation and basic workshop verification. This type of solution is often chosen as an economical alternative to new components, especially in vehicles used intensively, where a reasonable repair cost while maintaining functionality is important.

Before installation, it is recommended to:

• check the tightness of the fuel line connectors and ports,
• verify the condition of the pump's electrical connectors,
• inspect the interior of the tank for solid contaminants and deposits,
• use new gaskets and clamps in all disconnected areas.

This approach helps reduce the risk of leaks and ensures the proper operation of the supply system after replacement.

Technical support and further reading

To better understand the role of the fuel tank, pump, and other fuel system components in diesel engines, it is worth referring to our guide. A detailed discussion of diagnostics, selection by OEM numbers, and operating principles can be found in the article Fuel system – injectors, pumps, and fuel tank: maintenance and regeneration, which practically organizes the most important information.

If you are planning a comprehensive repair or upgrade of the fuel system area in your Mercedes and need other components from the same group, such as additional tanks, lines, or filler pipes, check the available parts in the Mercedes fuel tanks and filler pipes category.