Venting fuel filter
Model 1 15.1
1. Loosen venting screw (2) or with fuel filter without venting screw loosen hollow screw (2 and 4).
Model 123.1
Loosen hollow screw (3) and keep pumping with hand pump until fuel pumps out free of bubbles. Tighten hollow screw again.
2. Loosen actuating button (3) of manual delivery pump (on engine 61 7 in model 115.1 not required)
and keep actuating manual delivery pump until fuel emerges free of bubbles at vent screw (2) or hollow
screw (2 and 4). Tighten vent screw or hollow screw again.
Manual delivery pump
Engine 617 in model 115.1
Venting injection pump
3. M-injection pump with pneumatic governor. Loosen vent screw (arrow) on injection pump and also keep pumping with hand pump until fuel emerges free of bubbles. Tighten vent screw again.
4. M W and MIRSF-injection pump with mechanical governor. Keep pumping with hand pump until overflow valve on injection pump opens (audible buzzing noise).
5. Tighten actuating button of manual delivery pump again.
Note: This will force pump piston on a sealing ring and the hand pump is sealed in outward direction.
With actuating button released, the manual delivery pump will leak during operation and air may enter fuel system.
6. Run engine and check whether all connections are leaktight.