Injection timing control device and high pressure fuel pump sprocket (Mercedes-Benz C-Class W201)

Removal

Caution: To perform the operation described below to remove the device and the sprocket, the injection pump shaft must be secured with a specially configured device. Making such a device yourself with the required precision is too difficult and can cause internal damage to the fuel pump when used. Therefore, it is recommended to rent this tool from Mercedes-Benz dealers or from Bosch diesel fuel system specialists.

1. Disconnect the negative battery terminal

2. If necessary, remove the lower engine guard.

3. Remove the accessory drive belt in the following order.

• a) Remove the plastic plug, unscrew the mounting bolt and remove the accessory drive belt tension pulley.
• b) Loosen the mounting bolt and remove the radiator fan pulley.
• c) Unscrew the bolts and remove the tensioner damper spacer. Remove all gaskets and/or brackets from the bolts, remembering their location.
• d) Using pliers, unhook the tension spring, remembering its correct position to restore its assembly.
• d) If necessary, remove the plug and, after unscrewing the tensioner mounting bolt, pull out the sleeve on which the tensioner is mounted.
• e) Remove the tensioner and remove the gasket (if provided).

4. In accordance with Chapter 3, remove the radiator fan and its shroud.

5. In accordance with Chapter 9, remove the brake booster pump from under the camshaft timing chain cover. Note that the gasket must be replaced during installation.

6. Using a socket or wrench, turn the crankshaft in the direction of normal rotation by 15° after piston #1 reaches TDC using the pulley/damper-to-hub bolt. Use the pointer on the camshaft timing chain cover and the scale on the damper to determine the correct position (refer to Fig. 7.9).



7. If necessary, loosen the bolts and remove the sprocket retaining housing at the front of the fuel pump sprocket, (see fig. 8.7) On later models, the housing is held in place by a dowel pin. Remove the dowel by screwing an M6 bolt into its end. Then, place a sliding hammer or impact wrench on the head of the bolt and gradually remove the dowel.



8. Refer to Chapter 2B and do the following:

• a) Remove the cylinder head cover.
• b) Remove the camshaft drive chain tensioner.
• c) Loosen and remove the camshaft sprocket mounting bolt and washer.

9. Secure the relative positions of the camshaft sprocket and timing chain by pulling them together tightly using a nylon cable tie or similar.

10. Move the sprocket with the chain attached to it from the end of the camshaft and leave it inside the camshaft drive chain cover.

11. If not already done, remove the fuel pump sprocket retaining housing.

12 Lock the crankshaft by holding it with a socket or spanner on the pulley/damper to hub mounting bolt, then loosen and remove the fuel pump sprocket center bolt.

Note: This bolt has a left-hand thread. Remove the washer.

13. Using a socket or wrench, turn the crankshaft in the direction of normal rotation by 15 degrees after piston #1 reaches TDC using the pulley/damper bolt to the hub. Use the pointer on the camshaft timing chain cover and the scale on the damper to determine the correct position (see fig. 7.8).

14. Apply paint marks to indicate the relative positions of the chain and the fuel pump sprocket - these will serve as alignment marks during installation.

15. After this, to remove the chain and sprocket, you need to remove the chain from the sprocket teeth. To do this, make a device from a piece of thin metal: cut out a rectangle approximately 140x70 mm in size and bend it along a radius approximately equal to the radius of the fuel pump sprocket.

16. Insert this homemade device in front of the fuel pump sprocket, then spread it so that it pushes the chain off the sprocket teeth and leaves it in this position (see fig. 8.16).



17. With the sprocket teeth separated from the chain, remove the timing device together with the sprocket from the camshaft drive chain housing using large pliers or clamps.



18. Unscrew and remove the plug on the side of the fuel pump. Be prepared for possible fuel leakage and place a piece of rag near the plug hole that absorbs fuel well.

19. Using suitable grips, turn the fuel pump shaft in the normal direction of rotation, observing the movement of the regulator rotor through the plug hole. Continue to turn the shaft until the protrusion on the rotor aligns with the hole. In this position, the rotor should be fixed relative to the pump body with a special device from Mercedes-Benz (please see the note at the beginning of this paragraph) (see fig. 7.24). This step should not be neglected, as it is the only way to ensure the correct setting of the injection timing of the high-pressure fuel pump during assembly.

Caution: Be careful not to damage the pump shaft surface when clamping with the gripper jaws.

Installation

20. Installation is carried out in the reverse order of removal, taking into account the following points:

• a) Before installing the sprocket and injection timing device on the pump shaft, make sure that the crankshaft has not moved from the position corresponding to 15° after piston No.4 reaches the TDC position.
• b) Use the alignment marks made when removing the target to align the target and the fuel pump drive sprocket.
• c) Lock the crankshaft and tighten the fuel pump sprocket mounting bolt to the required torque, taking into account that the bolt has a left-hand thread.
• d) Before turning the crankshaft, remove the locking device from the hole of the pump injection timing adjustment device (and install the plug).
• d) Contact chapter 2B and install the camshaft sprocket. To ensure correct installation, make one full revolution of the crankshaft and check that the TDC timing marks on the crankshaft and camshaft are correctly aligned.
• e) If the brake vacuum pump has been removed, a new seal must be used when refitting it - for details, refer to chapter 9.
• g) Upon completion, check and, if necessary, adjust the fuel supply timing of the high-pressure fuel pump in accordance with paragraph 9.