The 7.3L Direct Injection Turbo (DIT) Engine uses a unique injection system. Absent from a normal diesel injection system are a mechanical injection pump and injection lines. New components include a high pressure oil pump and reservoir, pressure regulator for the oil and passages in the cylinder head for the flow of the fuel to the injectors.
Fuel is drawn from the fuel tank by a tandem fuel pump. The tandem fuel pump circulates fuel at low pressure through the fuel filter/water separator/fuel heater and then fuel is directed back to the fuel pump where fuel is pumped at high pressure into the cylinder head fuel galleries. The injectors are then fired by the PCM, which are controlled by the PCM but hydraulically actuated by the oil pressure from the high pressure oil pump.