General information
1. To ensure that the high-pressure fuel pump delivers fuel to each cylinder at the correct time during the engine's operating cycle, the fuel injection timing should be checked and, if necessary, adjusted. This check should always be performed after the fuel pump or any associated components have been disassembled.
2. There is an inspection hole on the fuel injection pump body, which is closed with a metal threaded plug in the working condition. Fuel injection into cylinder No.1 begins when the protrusion on the regulator rotor inside the fuel pump is located opposite the inspection hole.
3. When the projection is precisely aligned with the center of the hole, the position of the crankshaft can be determined using the pointer on the camshaft timing chain case and the scale on the crankshaft damper. The crankshaft rotation angle determined in this position provides an indirect determination of the fuel injection timing.
4. The best way to measure is electronically, using a sensor screwed into the fuel pump inspection hole. However, since such equipment is only available to Mercedes-Benz dealers and Bosch diesel fuel injection specialists, we describe an alternative method. It should be noted that this method only provides an approximate setting to start the engine - the car should be tested by specialists at the first opportunity to obtain accurate data.
Examination
5. Disconnect the negative battery terminal.
6. In accordance with chapter 3 remove the radiator fan and its shroud.
7. Unscrew the plug on the side of the fuel pump housing. Be prepared for possible fuel leakage and place a piece of rag that absorbs fuel well near the plug hole.
8. Using a small mirror, inspect the edge of the fuel pump rotor through the inspection hole.
9. Using a thorium wrench, turn the crankshaft in the direction of normal rotation by the pulley/damper mounting bolt to the hub until the protrusion on the governor rotor is precisely aligned with the center of the inspection hole (see fig. 7.24).
10. Without allowing the engine to turn further, determine the crankshaft rotation angle using the pointer on the camshaft timing chain cover and the scale on the crankshaft damper (see fig. 7.8).
11. Compare the obtained value with the one indicated in the paragraph "Technical data" and adjust if necessary. Replace the inspection hole plug and tighten to the specified torque.
Adjustment
12. In accordance with the previous subsection, manually turn the crankshaft until it reaches the position specified in paragraph "Technical data" nominal value of fuel injection moment.
13. Loosen the three bolts securing the fuel pump to the support flange. Similarly, loosen the bolt securing the rear of the pump to the support bracket (refer to paragraph 7).
14. Unscrew the plug on the side of the fuel pump housing. Be prepared for possible fuel leakage and place a piece of rag that absorbs fuel well near the plug hole.
15. Using a small mirror, inspect the edge of the fuel pump rotor through the inspection hole. Using a thorium wrench, turn the crankshaft in the direction of normal rotation by the pulley/damper mounting bolt to the hub. Turn the fuel timing adjustment screw until the protrusion on the regulator rotor aligns exactly with the center of the inspection hole (see fig. 9.15).
Fig. 9.15. Fuel injection timing adjustment screw (shown with an asterisk) on the fuel injection pump
Note: Turn the adjusting screw to the right if the fuel supply switching moment is delayed; turn the screw to the left if the fuel supply switching moment is ahead of the nominal value.
18. Once alignment is achieved, tighten the front and rear fuel pump mounting bolts to the recommended torque values.
17. Replace the inspection hole plug and tighten to the specified torque.
18. Please note that this method only provides the preliminary adjustment necessary to start the engine - the engine should be tested and adjusted by Mercedes-Benz dealers or Bosch specialists at the earliest opportunity.