| It ensures pressure is constant in high pressure accumulator and in injector lines. |
| 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 -N 276- cannot be re-used. |
| »Carry out the following work sequence« |
WARNING | t
| Always observe rules for cleanliness and instructions when working on fuel system → Chapter. |
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| Always follow these rules for cleanliness and instructions before starting work and while working on the fuel system. |
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| Remove high-pressure accumulator → Chapter. |
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| Clean threaded area around fuel pressure regulating valve -N 276- (e.g. with standard cleaning solution) before removing. |
| Under no circumstances may dirt enter the hole on the high-pressure accumulator element (high-pressure accumulator). |
Note | Clean carefully; cleaning solvent must not enter the electrical connector. |
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| Dry fuel pressure regulating valve -N 276-. |
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| Slacken union nut (counterhold at hexagonal flats on housing). Then unscrew and remove by hand. |
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| Extract dirt from threads and sealing surfaces. Do not use mechanical tools, etc. |
Note | Seal off drilling immediately with a suitable plug to prevent dirt from entering. |
Note | t
| The fuel pressure regulating valve -N 276- 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 -N 276- are not damaged. |
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| Check sealing surface of drilling. |
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| Lubricate thread and deformable sealing lip of fuel pressure regulating valve -N 276- with Molybdenum grease. |
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| Screw on union nut by hand. |
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| Align new regulating valve so that the connecting line is free of tension after connector is attached. |
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| Hold regulating valve in this position with an open-end spanner on housing hexagon or use for example multi slip-joint pliers for this. |
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| To tighten union nut, use a suitable torque wrench with a 36 mm open-end spanner insert. |
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| Install high-pressure accumulator → Chapter. |
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| Check fuel system for leaks. |
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| Connect vehicle diagnostic tester. |
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| Read event memory and erase stored event entry if necessary. |
Note | t
| If the fuel pressure regulating valve -N 276- or the high-pressure pump has been exchanged, it is essential that the programmed values for the regulating valve be reset using the vehicle diagnostic tester. |
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| Perform the function „Resetting engine control unit programmed values“ in „Guided functions“. |
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| After installation, run engine at moderate speed for several minutes and then switch off. |
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| Then test drive the vehicle, accelerating to full throttle at least once. |
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| Then check high-pressure part of fuel system again for leakage. |
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| Read event memory again. |
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