| Removing and installing fuel pressure regulating valve |
| The fuel pressure regulating valve is located in the high pressure accumulator. The valves ensure that pressure is constant in the high pressure accumulator and in the injector lines (fuel high pressure circuit). |
| If pressure is too high in the fuel high pressure circuit, the regulating valve will open. A small amount of fuel from the high pressure accumulator will thereby make its way back to the fuel tank via the return line. |
| If pressure is too low in the fuel high pressure circuit, the regulating valve will close. The valve seals the high pressure side against the low pressure side in this way. |
Caution | Follow the rules for all work on the fuel system → Chapter. |
| Follow these instructions before starting work and while working on the fuel system. |
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| Clean threaded area around regulating valve (e.g. with standard cleaning solution) before removing. Under no circumstances may dirt enter the hole of the high pressure accumulator (rail element). |
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| Clean carefully; cleaning solvent must not enter the electrical connector. |
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| The fuel pressure regulating valve -N276- cannot be re-used. |
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| Dry off fuel pressure regulating valve -N276-. |
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| Disconnect electrical connector from fuel pressure regulating valve -N276-. |
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| Counterhold at housing hexagon and loosen union nut. Then unscrew and remove by hand. |
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| Extract dirt from high-pressure accumulator bore (threads and sealing surface). Do not use tools or other instruments for this purpose. |
Note | Seal off high-pressure accumulator hole immediately with a suitable plug to prevent dirt from entering. |
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| Check that sealing surfaces (deformable sealing lip) and threads on fuel pressure regulating valve -N276- are undamaged. |
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| Also check sealing surface at high-pressure accumulator bore. |
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| Thread on fuel pressure regulating valve -N276- must be free of oil and grease. |
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| Screw on union nut by hand. |
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| Align fuel pressure regulating valve -N276- so that connecting wire is free of mechanical tension after electrical connector is attached. |
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| Counterhold at housing hexagon and tighten union nut. Specified torque → Item |
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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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| Then test drive the vehicle with at least one full acceleration. Check high pressure part of fuel system again for leaks. |
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