| 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 -N276- 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 -N276- closes. |
| This seals the high-pressure side against the low-pressure
side. |
Note | The fuel pressure regulating valve -N276- 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. |
| t
| Always follow these rules for cleanliness and instructions
before starting work and while working on the fuel system. |
|
| –
| Removing high-pressure accumulator → Chapter. |
| –
| Clean threaded area around fuel pressure regulating
valve -N276- (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. |
| –
| 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. |
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
| Check that sealing surfaces (deformable sealing lip) and threads
on new fuel pressure regulating valve -N276- are not damaged. |
| t
| Check sealing surface of drilling. |
| t
| Lubricate thread and deformable sealing lip of fuel
pressure regulating valve -N276- with Molybdenum
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. |
| –
| To tighten union nut, use a suitable torque wrench with
a 36 mm open-end spanner insert. |
| –
| Install high-pressure accumulator → Chapter. |
| t
| Specified torques: assembly overview - fuel system → Chapter. |
| –
| Check fuel system for leaks. |
| –
| Connect vehicle diagnosis tester. |
| –
| Read event memory and erase stored event entry if necessary. |
Note | t
| If the fuel pressure regulating valve -N276- 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. |
| –
| Read event memory again. |
|
|
|
