TM 10-3930-660-34 c. Fuel Injection Pump. The injection pump is a rotary distributor pump. The pump uses a single rotor to develop and distribute the high pressure required for injection. This pump performs the following functions: (1) Produces high fuel pressure required for injection. (2) Meters exact amount of fuel for each injection cycle. (3) Distributes high pressure metered fuel to each cylinder at the precise time. (4) Changes distribution time relative to engine speed. d. Fuel Injectors. The fuel injectors are Robert Bosch, 17mm closed nozzle, hole-type injectors. During the injection cycle, high pressure from the injection pump rises to operating (pop) pressure which causes the needle valve in the injector to lift. Fuel is then injected into the cylinder. A shimmed spring is used to force the needle valve closed as the injection pressure drops below the pop pressure to seal off the nozzle after injection. 4-2