Injector Nozzles
The injectors are liquid-controlled, throttling pintle-nozzle injectors. The injector consists of a nozzle holder and nozzle needle which is screwed in the cylinder head and connected on the distributor injection pump by a high pressure line. See Fig 1.
The high-pressure fuel is delivered into pressure chamber of a fuel injector through an annular groove and feed bore. When the injection pressure, which presses down on the shoulder of nozzle needle, exceeds the spring force in the nozzle holder, the needle will lift off of its seat, and fuel is injected into the turbulence chamber.
The contour of the spray nozzle on throttling pintle-nozzle injectors is not cylindrical, but has various restrictions. When injecting fuel, the nozzle first sprays a small initial amount of fuel, which vaporizes in the turbulence chamber and ignites. Immediately afterwards, the main amount of fuel is injected and combustion can be started. This type of injector version guarantees smoother engine running. In other words, the "knocking" of the diesel engine is reduced. See Fig 2.
All fuel injectors are connected with each other by a fuel leak line, so that fuel leaking past the nozzle needle can be returned to the fuel tank without pressure.
The fuel injectors are combined with nozzle holder and nozzles. These units cannot be repaired. The BMW diesel is the only engine that uses an electric coil and 2 wire outlets. An electric signal is transmitted for each movement of the nozzle needle. This signal is used to determine the beginning of injection and the duration for optimal engine operation. See Fig 3.