The following explanation of how a rotary fuel pump works was provided by DBTC member “Erkki":- The heart is rotor+rotor housing , part 39. The rotor rotates like a distributor in a petrol engine, there are holes in the housing which lead fuel to the injector lines. In the right position, the hole in the rotor is correctly aligned with the hole in the housing, and that is when the pump drives fuel to the injection lines. You can see a roller above the rotor. There are two rollers on opposite sides of the rotor. Between them are bearing plates and below the bearing plates the high pressure pistons move face to face in a bore inside the rotor. The rollers roll over a cams on the cam ring, part 57. When there is just round wall the rolls have larger distance between them and the high pressure cylinder inside the rotor gets fuel in. When the rolls come to the starting point of injection, the cams are just in front of the rollers, and turning slightly forward, the rolls jump over the cams and press the high pressure pistons towards each others, the fuel gets pressurized and bursts to the injection line. To make the fuel flow between the high pressure pistons, a interpressure is required inside the pump housing, which presses the high pressure pistons aapart on plain round part of the cam ring. Interpressure is made by cross blade pump on the back end of the injection pump. The blades are part 34 and they rotate inside the housing 36. The housing is slightly non-centric to the rotor shaft, which makes the cross blades slide in their slots and produce fuel flow. Interpressure is limted by mechanical valve, part 18 A. Throttle is made by a tiny valve, part 182. It can be turned in its bore. In one end it closes the interpressure from high pressure side. On the opposite its lets full flow there and between the extremeties the engine gets the fuel amount which is regulated by throttle pedal and mechanical governor in the front end of the rotor.