| The fuel pressure regulating valve -N276--6- is located in the fuel rail. It maintains a constant pressure in the fuel rail and the injector pipes. |
| If the pressure in the high-pressure fuel circuit is too high, the fuel pressure regulating valve -N276- opens to allow some of the fuel to flow back from the fuel rail to the fuel tank via a return line. |
| If the pressure in the high-pressure fuel circuit is too low, the fuel pressure regulating valve -N276- closes and seals off the high-pressure section of the system from the low-pressure section. |
Note | The fuel pressure regulating valve -N276- cannot be re-used. |
WARNING | t
| Always observe rules for cleanliness and instructions for working on fuel system → Chapter. |
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| Follow these instructions and rules for cleanliness before starting work and while working on the fuel system. |
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| Before removal, clean area around thread for fuel pressure regulating valve -N276- using commercial cleaning solution or similar (no dirt must enter opening in fuel rail). |
Note | Clean carefully; cleaning solution must not enter the electrical connector. |
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| Dry off fuel pressure regulating valve -N276-. |
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| Loosen fuel pressure regulating valve -N276-. Then unscrew and remove by hand. |
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| Remove dirt from thread and sealing surface using vacuum cleaner. Do not use metal tools, etc. |
Note | Seal off hole immediately with a suitable plug to prevent dirt from entering. |
Note | t
| The fuel pressure regulating valve -N276- has a deformable sealing lip and no separate seal; it can therefore be used only once. |
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| Check that sealing surfaces (deformable sealing lip) and threads on new fuel pressure regulating valve -N276- are not damaged. |
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| Check sealing surface at bore. |
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| The beginning of the thread and the deformable sealing lip of the fuel pressure regulating valve -N276- must be coated with diesel fuel. |
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| Use suitable torque wrench with an open-end spanner insert (36 mm) to tighten. |
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| Tightening torque: refer to fuel system - exploded view → Chapter |
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| After installation, run engine at moderate speed for several minutes and then switch off. |
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| Check fuel system for leaks. |
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| Interrogate event memory. |
| After renewing high-pressure pump and/or fuel pressure regulating valve -N276-, adaption must be performed. (The procedure is also described in Guided Functions) |
| Select correct vehicle identification in Guided Fault Finding. |
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| Press „Function/component selection“. |
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| „01 - Self-diagnosis compatible systems“ |
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| „01 - Engine electronics J623“ |
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| Select „01 - Engine electronics functions“ |
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| „01 - Adapt learnt values“ |
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| After completing the repair, road-test the vehicle. Accelerate with full throttle at least once. Then check the high-pressure section of the fuel system again for leaks. |
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| Interrogate event memory again. |
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