MW-pump and RW governor
The MW-pump is a highly complex and precise mechanical device, capable of pressurizing, timing, and metering fuel. It is mated in this case, to the RW governor, an even more complex device. Together, they comprise the fuel injection pump. Detailed information can be found in the MW and RW chapters of the Bosch Diesel Training course. For each section, an explosion diagram is provided, as well as a higher quality explosion diagram and parts list in PDF format.
A crude explanation of the pump section, would be that it is a mini inline-5 engine that runs at half the speed of the engine that has variable cylinder displacement, which is used to inject variable quantities of fuel into the engine. The major parts are the camshaft (4), rack (12), and fuel elements (111). The fuel elements are phased with shims (split shims shown here, 50), and delivery is adjusted by twisting the elements. In order to calibrate the pump and governor a set of detailed test specifications is used, which specific to the pump and governor combination. Rebuilding a pump and calibrating it is incredibly difficult, and is supposed to require a Bosch test bench which can cost hundreds of thousands of dollars. The pump used on the OM617.952 (and possibly others) is the PES5MW55/320RS16-1, Bosch PN 0 413 255 989.
A crude explanation of the governor section, would be that it is a set of weights, which extend outwards as the engine speeds up. As this happens, they interact with springs and levers to control the rack. The weights are pulling the rack back, and the springs pull it forwards. By tuning a variety of linked adjustments, the governor can have a tuned fueling curve. The RW governor used on the OM617.952 (and possibly others) is the RW375/2200MW28-3, Bosch PN 0 420 081 023.
Fuel Lift Pump
The Fuel Lift Pump is a positive displacement pump used to pressurize the MW-pump body to a nominal 14psi, regulated by the fuel pressure relief valve. The valve spring is known to weaken and compress over time. The FSM calls for a spring length of 27mm, tolerance of 1mm. It is known that performance increases can be had by increasing the pressure, possibly to a spring length of 30mm or more, which can cause adverse effects due to harmonics in the fuel system. There is a manual pump present on this lift pump, and there is a new and old style. The old style is incredibly prone to leakage, and show be replaced with the new style (Bosch PN 2 447 222 126). The lift pump used on the OM617.952 (and possibly others) is the RP/K22MW22, Bosch PN 0 440 017 022.