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Removing and installing fuel pressure senderG247 > < Removing and installing rail element (high-pressure reservoir)

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Removing and installing fuel pressure regulating valveN276
Removing and installing fuel pressure regulating valve -N276-
Special tools and workshop equipment required
t  Torque wrench
t  Open-ended wrench socket, 36 mm
   
The fuel pressure regulating valve -N276--6- is located in the common rail (high-pressure reservoir) and it maintains a constant pressure in the common rail (high-pressure reservoir) and the injector pipes.
If pressure is too high in the fuel high-pressure circuit, fuel pressure regulating valve -N 276- opens.
As a result a small amount of fuel from the high-pressure accumulator will make its way back to fuel tank via the return line.
If pressure is too low in fuel high-pressure circuit, fuel pressure regulating valve -N 276- closes.
This seals the high-pressure side against the low-pressure side.
  Note
The fuel pressure regulating valve -N276- cannot be re-used.
Removal:
  WARNING
t  When carrying out work on the fuel system, always observe the guidelines for cleanliness and the instructions → Chapter.
t  Follow these instructions and rules for cleanliness before starting work and while working on the fuel system.
  A23-10420
–  Loosen the engine cover at the locations -arrows- and remove.
–  Remove rail element (high-pressure accumulator) → Chapter.
–  Before disassembling clean the area of the thread around the regulation valve for fuel pressure -N276- (for e.g. with a commercial cleaning agent). No dirt must enter the hollow space in the common rail (high-pressure reservoir).
  Note
Proceed carefully. The cleaning agent should not enter in the connection.
–  Dry fuel pressure regulating valve -N276-.
–  Slacken union nut (counterhold at hexagonal flats on housing). Then unscrew and remove by hand.
–  Extract dirt from threads and sealing surfaces. Do not use metal tools, etc.
  Note
Seal off drilling immediately with a suitable plug to prevent dirt from entering.
Installation
  Note
t  The fuel pressure regulating valve -N276- has a deformable sealing lip and no separate seal; it can therefore be used only once.
t  The sealing surfaces (bite-edge sealing) and thread of the new regulation valve for fuel pressure -N276- must not be damaged.
t  Check sealing surface of drilling.
t  The beginning of the thread and the deformable sealing lip of the fuel pressure regulating valve -N276- must be lubricated with Molykote grease.
–  Screw on union nut by hand.
–  Align new regulating valve so that the connecting line is free of tension after connector is attached.
–  Hold regulating valve in this position with an open-end spanner on housing hexagon or use for example multi slip-joint pliers for this.
–  Use suitable torque wrench with an open-end spanner insert (36 mm) to tighten union nut.
–  Install rail element (high-pressure accumulator) → Chapter.
t  Tightening torques: Fuel system - Component overview → Chapter
–  Let the engine run for a few minutes at average speed after the assembly and then switch it off again.
–  Check the entire fuel system for leaks.
–  Read out the event memory
  Note
t  If the fuel pressure regulating valve -N 276- or the high-pressure pump has been exchanged, it is essential that the learnt values for the regulating valve be reset using the vehicle diagnosis tester.
t  Perform the function „Resetting engine control unit programmed values“ in „Guided functions“.
–  After installation, run engine at moderate speed for several minutes and then switch off.
–  Then test drive the vehicle, accelerating to full throttle at least once.
–  Then check high-pressure part of fuel system again for leakage.
–  Interrogate event memory again.
  E10-10087

Removing and installing fuel pressure senderG247 > < Removing and installing rail element (high-pressure reservoir)