The Mercedes W639 W906 OM646 Diesel Injection Rail is a fuel supply system component designed for diesel engines, used in Mercedes vehicles with the OM646 unit. A used injection rail allows for an economical yet technically correct repair of the common rail system in vans and passenger cars of this series.
Specifications and technical data
- SKU: A6400702595
- Mark: Mercedes (Genuine OE)
- Condition: Used
- OEM Part Number: A6400702595
- Substitutable numbers: A6400702595, A 640 070 25 95, KZ
- Fuel type: Diesel
- Category: Fuel Injectors
Purpose and Role in the Injection System
The injection rail for the OM646 diesel engine is responsible for the even distribution of high-pressure fuel to individual injectors. In common rail systems, stable rail pressure is crucial for correct fuel delivery, smooth engine operation, and reduced smoke and fuel consumption.
In Mercedes W639 and W906 vehicles, a properly functioning injection rail directly impacts:
- stable diesel engine operation across the entire RPM range,
- precise injection control during cold and hot starts,
- maintaining adequate fuel pressure throughout the common rail system.
Category: Injector Nozzles and Fuel Supply System Components
Although the product is categorized under Injector Nozzles, it is in practice a central element of the fuel supply line in a diesel engine. Replacing the injection rail is often performed concurrently with injector diagnostics or refurbishment when issues arise with fuel pressure, uneven engine operation, or engine control unit errors.
Selecting a rail dedicated to the specific OM646 engine series in Mercedes W639 and W906 ensures:
- compliance with the factory operating characteristics of the injection system,
- proper interaction with sensors and accessories controlling fuel pressure,
- hassle-free installation in place of the original component.
Technical Characteristics and Installation
The injection rail is designed for engines powered by diesel fuel, operating with common rail technology. The rail's design allows for the connection of high-pressure lines leading to individual injectors and interaction with the pressure sensor and regulator valve (depending on the specific vehicle configuration).
When installing, pay attention to:
- cleanliness of the fuel system – the system should be free of contaminants before installing the rail,
- correct tightening of high-pressure lines according to service recommendations,
- leak testing after the initial engine start.
A used injection rail is a good solution when the original component has suffered mechanical damage or there are problems maintaining fuel pressure, and you wish to limit repair costs while maintaining an appropriate level of quality.
Benefits of Using the Mercedes W639 W906 OM646 Injection Rail
Using a dedicated injection rail in the OM646 diesel engine restores the correct operating parameters of the fuel supply system. The most significant benefits include:
- restoring stable fuel pressure across the entire load range,
- improving engine smoothness – reducing jerking and uneven idling,
- better throttle response due to proper fuel delivery,
- reducing the risk of further damage to injectors and common rail accessories.
In conjunction with properly functioning injectors and a high-pressure pump, the injection rail is a vital component ensuring the durability and predictable performance of the engine in daily operation.
Injection System Diagnostics and Prevention
When experiencing issues with the common rail system – such as difficult starting, loss of power, or excessive smoke – it is advisable to perform a full diagnostic of the injectors and injection rail. A detailed discussion of symptoms and potential consequences of neglect can be found in the article: Diesel Injector Failures – How to Recognize Them and What Their Neglect Entails. This provides practical knowledge for planning diesel engine fuel system repairs.
Mercedes Injector Nozzles – Selection and Alternatives
If you are looking for other components from the Mercedes injector nozzles category for your vehicle, please visit our dedicated subpage: Mercedes injector nozzles. There you will find a wide selection of injection system components tailored to various models of this brand.
For used parts, it is also worth consulting our guide, which helps you make informed choices about second-hand components and assess their value compared to new replacements: Used Parts – Your Guide to the Best Deals in the Automotive Store. This will help you plan your injection system repair more effectively from both a technical and budgetary perspective.
