| The fuel pressure regulating valve -N276--arrow- is located in the fuel rail. It maintains a constant pressure in the fuel rail and the injector pipes (high-pressure fuel circuit). |
| If the pressure in the high-pressure fuel circuit is too high, the regulating valve 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 | Fuel pressure regulating valve -N276- must always be renewed after it has been removed. |
Caution | Risk of malfunctions caused by dirt. |
|
| –
| 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. |
| –
| Dry off fuel pressure regulating valve -N276-. |
| –
| Slacken union nut (counterhold at hexagon flats on housing). Then unscrew and remove by hand. |
| –
| Extract dirt from opening in fuel rail (thread and sealing surface) using a vacuum cleaner. Do not use metal tools, etc. |
| –
| Seal off opening in fuel rail with a clean plug. |
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 at opening in fuel rail. |
| t
| The beginning of the thread and the deformable sealing lip of the fuel pressure regulating valve -N276- must be coated with diesel fuel. |
| –
| Screw on union nut by hand. |
| –
| Align new regulating valve so that connecting wire is free of tension after connector is attached. |
| –
| Hold regulating valve in this position by holding hexagon flats on housing of regulating valve with open-end spanner or pliers (water pump pliers or similar). |
| –
| Use suitable torque wrench with an open-end spanner insert (30 mm) to tighten union nut. |
| –
| After installation, run engine at moderate speed for several minutes and then switch off. |
| –
| Check fuel system for leaks. |
| –
| Interrogate event memory. |
| –
| 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. |
| –
| Interrogate event memory again. |
|
|
|
