Connect the auxiliary hose -3- to the fuel return line of the fuel rail -2-. Connect this hose -3- to a suitable container in order to measure the fuel flow in the fuel return line.
1. Checking with the engine running
Start the engine and leave it to idle. Nominal value: after 30 seconds more than 75 ml. If the nominal value is not reached, the fuel pressure control valve -N276- is defective.
2. Checking with the engine running
If the clause condition (1) done, increase the engine speed to 2000 rpm. Set return volume: 0 ml. Drip leakage is acceptable. If the nominal value is not reached, the fuel pressure control valve -N276- is defective.
3. If the engine does not start
Carry out a test at starter speed. Set return volume: 0 ml. Drip leakage is acceptable. If the nominal value is not reached, the fuel pressure control valve -N276- is defective. Renew fuel pressure regulator -N276-.
Replacing fuel pressure regulator -N276-
The fuel pressure regulator -N276- is located in the fuel rail and serves to maintain a constant pressure in the fuel rail and high pressure lines (high pressure fuel circuit). If the pressure in the high-pressure fuel circuit is too high, the pressure regulator valve opens and part of the fuel from the fuel rail flows back into the fuel tank through the fuel return line. When the pressure in the high pressure fuel circuit becomes too low, the pressure regulator closes and separates the high and low pressure circuits.
Note: The fuel pressure regulator -N276- must not be reused.
Remove the top engine cover. Release fuel return hose -1-. Open retaining clips -arrows-, detach and remove guide well -2-. Before removing, clean threaded area around fuel pressure regulator -N276-. Do not allow dirt to enter the fuel rail opening. Work carefully - do not allow the cleaner to get on the electrical connector. Dry fuel pressure regulator -N276-.
Disconnect connector -2-. Loosen union nut -1-, to do this, hold the hexagon on the fuel rail against turning. Then unscrew the regulator by hand. Pump out impurities from the opening of the pressure accumulator (clean thread and sealing surface). Do not use mechanical tools for this. Close the open fuel rail connection with a clean plug.
Installation
Note: Replace fuel pressure regulating valve -N276- every time it is removed. Moisten threaded part and crushing lip of fuel pressure regulator -N276- with diesel fuel.
Tighten the union nut by hand. Install the new fuel pressure regulator so that the wiring harness is not under tension after connecting the connector. Hold the pressure regulator in this position by the hexagon of the body with an open-end wrench or, for example, a pipe wrench. To tighten the union nut, use a suitable torque wrench with a 30 mm open-end wrench. Fill the fuel system with fuel/bleed air from the fuel system.