Fuel Pressure Regulator: Service and Repair

Fuel Pressure Regulator Valve (N276)

Special tools, testers and auxiliary items required

• Socket wrench

• 30 mm wrench

• Pliers (for example, water pump pliers)

The fuel pressure regulator valve - 1 - is located in the right rail (cylinder bank 1) and maintains a constant pressure inside the rail and in the injector lines (fuel high pressure circuit).






If the pressure in the high pressure fuel circuit is too high, the regulator valve will open so that some of the fuel flows from the fuel rail back into the fuel tank via a return line.

If the pressure is too low, then the check valve closes and seals off the high pressure side from the low pressure side.

The fuel pressure regulator valve cannot be used again.

Removing

Follow the guidelines for a clean working environment when working on the fuel system. Refer to => [ Clean Working Conditions ] Clean Working Conditions.

Always follow these instructions before and during work.

- Remove engine cover. Refer to => [ Engine Cover ] Service and Repair.

- Before removing, clean the threaded area around the fuel pressure regulator valve with a commercially available detergent. Dirt must not enter the hole in the fuel rail.

• Clean carefully, cleaner must not enter the connector.

- Dry the fuel pressure regulator valve.

- Remove the banjo fitting for the fuel return lines.

- Disconnect the connector from the fuel pressure regulator valve.

- Counter hold at the housing hex bolt and loosen the union nut. Then remove it by hand.

- Suction any dirt out of the hole, the threads and the sealing surface. Do not use mechanical tools.

• Seal the hole in the fuel rail immediately with a plug to prevent dirt from entering.

Installing

• The fuel pressure regulator valve has a biting edge instead of a sealing ring and cannot be reused.

• Check the new fuel pressure regulator valve sealing surface and threads for damage.

• Check the sealing surface on the hole in the fuel rail.

• Coat the fuel pressure regulator valve threads and biting edge with diesel fuel.

- Tighten union nut by hand.

- Align the check valve so that the connection line is not taut after connecting the connector.

- Hold the check valve housing hex bolt in this position with pliers (for example, water pump pliers).

- Use a torque wrench with a 30 mm wrench to tighten the union nut.

Tighten the Union Nut in 4 Steps.






- Tighten the banjo fitting with new seals.

Fuel System, Bleeding and Performing a Leak Test

- After installing, let the engine run at a moderate speed for a few minutes and then stop it.

• The high pressure connections must "not" be opened; the fuel system bleeds itself.

- Check Diagnostic Trouble Code (DTC) memory and erase, if necessary.

- Turn off ignition.

- Carefully check the entire fuel system for leaks.

If there are leaks even though the correct tightening specification was used, replace the affected component.

Perform an adaptation after replacing the high pressure pump and / or the fuel pressure regulator valve. The procedures are also described in Guided Fault Finding.

- Perform a road test where the accelerator pedal is pressed all the way down at least one time. Then check the high pressure area again for leaks.

• If there is still air in the fuel system, the engine may switch to emergency mode during the road test. Turn off the engine and erase the DTC memory. Then continue the road test.

- After the road test, check the DTC memory again.