Pre-combustion Chamber: Service and Repair

Removal





Model 116.120

1 Disconnect regulating linkage to remove cylinder head cover. Pull out locking eye of longitudinal regulating shaft (arrow).






Model 123

On models 116.120 and 123, pull longitudinal regulating shaft out of rubber mount in forward direction and remove in rearward direction.






Model 126.120.

On model 126.120, pull longitudinal regulating shaft out of guide lever in rearward direction and remove in forward direction.

On models 123 with automatic transmission 722.303 (W4A 040) and 126.120, pull off central plug for vacuum lines (71) or vacuum lines. Disconnect bowden wire, compress black plastic clip (arrow) and pull bowden wire out of holder in rearward direction.






2 Remove injection lines.
3 Pull fuel return hoses from injection nozzles.






4 Unscrew complete nozzle holder by means of socket (27 mm).






46 Cylinder head gasket
50 Threaded ring
51 Pre-chamber
52 Sealing ring
53 Nozzle reed
80 Nozzle holder
81 Rod-type glow plug

5 Unscrew rod-type glow plugs (81).
6 Unscrew threaded ring (50) by means of socket wrench.






03 Screw insert

For this purpose, screw insert (03) into threaded ring, place sleeve (02) into grooves of threaded ring (arrows) and tighten with nut (01).






01 Nut
02 Sleeve

Sleeve (02) should be seated in grooves tight enough to prevent slipping out of grooves when the threaded ring is released.

Position wrench against hex. head of sleeve (02) and unscrew threaded ring.










01 Spindle
02 Nut
03 Bell

7 Pull-out pre-chamber by means of puller. Screw spindle (01) into pre-chamber. Place bell-shaped member (03) on cylinder head. The contact surface of the bell-shaped member is provided with 2 lugs. One lug each should be seated in hex. or double hex. socket of cylinder head bolt adjacent to prechamber. Pull-out prechamber by rotating nut (02) with an open-end wrench.






8 Remove sealing ring (arrow) from cylinder head.
9 Cover bore in cylinder head.


Installation

NOTE: If the removed pre-chambers are installed again, check for perfect condition.

Ball pin should not be burnt or scaled.

In addition, if burner tops are scorched or if prechamber lower half shows cracks, remove boost air pipe and check inside for traces of oil.

If oil-moist spots are found, check diaphragm of vacuum pump on engine 617.950 (USA) up to 1979 for cracks and other damage or renew vacuum control unit on injection pump of all engines.

The faulty component is identified by means of the vacuum lines (blackened by oil).






10 Place new sealing ring (52) into cylinder head. Use original sealing ring of specified thickness and shape only, so that the required distance (c) of 7.8 - 8.4 mm between pre-chamber and cylinder head is maintained.

NOTE: If a cylinder head has been faced at parting surface, add thicker sealing rings (52) between cylinder head and pre-chamber when installing prechambers.






The following sealing rings are available:

Thickness Part No.
1.9 - 2.1 (standard) 615 017 00 60
2.2 - 2.4 615 017 01 60
2.5 - 2.7 615 017 02 60
2.8 - 3.0 615 017 03 60






11 Screw spindle (01) of puller into pre-chamber (image step 7). Position pre-chamber in such a manner that the lug faces recess in cylinder head (arrows).

Insert prechamber by means of light blows with a plastic hammer against spindle. Pull bell-shaped member (03) with one hand in upward direction and hold in place (image step 7).






53 Nozzle plate
80 Nozzle holder
81 Pencil element glow plug

12 Lubricate threaded ring (50) and tighten to specified torque of 150 - 180 Nm by means of pertinent socket wrench.
13 Screw-in pencil element glow plugs and connect.
14 Insert new nozzle plate (53 Fig. step 5). The resilient nozzle plate can be installed on all engines.






15 Completely screw-in nozzle holder and tighten to 70 - 80 Nm.
16 Install injection lines.
17 Plug fuel return hoses to injection nozzles.
18 Mount cylinder head cover.