Fuel System - Operation and Tests/Distributor Injection Pump CTM3274 (01JUL99) 220-11 Saran Liter Engines 060799 PN=350 STANADYNE FUEL INJECTION PUMP (DM4) - OPERATION Fuel is delivered to the transfer pump inlet (1) where The speed advance adjusts timing of the fuel injection it passes through inlet screen (2) and enters the pump in relation to engine speed and load. vane-type pump (3).
Since the transfer pump displacement greatly exceeds the injection With the exception of the drive shaft bearing on DM4 requirements, a large percentage of fuel is by-passed models, lubrication of pump working parts is achieved through the regulator assembly (4) to the suction by means of fuel by-passed from the transfer pump side. This positive displacement pump causes fuel before it is returned to the fuel tank. The drive shaft flow to increase with speed and, because of the bearing on DM4 models is lubricated by engine oil regulating piston, pump pressure also increases with from the timing gear housing. speed.
As fuel leaves the transfer pump, it is directed Fuel under transfer pump pressure flows past rotor through a passageway leading to an annulus in the retainers (5) into an annulus on the rotor. It then hydraulic head. Connected to this passageway is a flows through a connecting passage (6) in the head vent passage located behind the metering valve bore. to the advance (8) and charging circuit (7). The fuel This vent passage contains a vent wire to prevent flows around the annulus through a connecting excessive return fuel flow and high pressure loss. A passage to the metering valve (10).
The radial short passage connects vent passage with governor position of metering valve (controlled by the governor) linkage compartment. Should air enter the transfer regulates flow of fuel into charging ring (12) which pump, it immediately passes to the vent passage. Air incorporates the inlet passages. and a small quantity of fuel then flow from the housing to the fuel tank by way of the return pipe. As rotor revolves, the two inlet passages (9) register with inlet passages in hydraulic head, allowing fuel to IMPORTANT: Remember that all adjustments to flow into the pumping cylinders.
With further rotation, the injection pump - except for slow inlet passages move out of registry and discharge idle - must be carried out on a test port of rotor registers with one of the head outlets. bench by a specialist injection pump While discharge port is opened, rollers contact cam repair station only. Internal lobes, forcing plungers together. Fuel trapped adjustments in the field are not between plungers is then delivered to the fuel permitted, as this pump is a sealed injection nozzle. unit. To obtain the best possible performance over the entire speed range, the fuel injection pump is fitted with an automatic advance system, hydraulically actuated. It is pre-set at the factory.
CD,3274,G220,8 -19-01FEB94 220 11