Fuel System - Operation and Tests/Distributor Injection Pump CTM3274 (01JUL99) 220-7 Saran Liter Engines 060799 PN=346 LUCAS CAV FUEL INJECTION PUMP - OPERATION General information A pressurizing valve is located at each outlet in the The Lucas CAV fuel injection pump is a horizontally pump head (as on in-line type fuel injection pumps) installed distributor pump with mechanical governor where the pressure line leading to the fuel injection and automatic hydraulic speed advance. The moving nozzle is connected.
After injection the pressure parts of the pump are simultaneously lubricated and regulating valve closes again and with its small relief cooled by the diesel fuel flowing through the pump. piston sucks a quantity of fuel from the pressure line. No lubricant is required. Four pump models are used: The resulting relief in pressure in the pressure line • DPA2 - 2 plungers causes a quick and firm shutting of the nozzle valve, • DPA4 - 4 plungers thus preventing fuel from leaking into the combustion These pumps are progressively replaced by the chamber. following pumps which are designed to meet future emission requirements:
The quantity of fuel which is needed at any given • DP200 - 2 plungers moment for each cylinder and combustion cycle is • DP201 - 4 plungers regulated by a metering valve which is controlled via speed control rod and control lever (8), by the Transfer pump and metering governor inside housing (5). The diesel fuel for injection is fed to the cylinders - regardless of their number - by a single unit. Its In the engine “shut-off” position, the metering valve pump and distributor rotor is fitted with two opposed completely cuts off the supply of fuel from transfer plungers controlled by a cam ring. On the other end pump to the rotor.
of the rotor, opposite the two pump plungers, there is a transfer pump which delivers the fuel, drawn from At idling speed or under load, the transfer pump the fuel filter, through the metering valve into the inlet feeds more fuel to the metering valve than is needed passage (13) in the pump head, at a pressure which for injection. The excessive fuel flows through the varies with engine speed. pressure regulating valve back to the suction side of the transfer pump. A very small amount of this Filling process: surplus fuel escapes through the top of the governor As rotor (15) rotates, inlet passage (13) in pump housing. head aligns with inlet passage (28) in the rotor.
Fuel coming from the transfer pump reaches the pump Automatic advance (speed responsive) plunger chamber through inlet passage (28), regulated by the metering valve and forces the two To obtain the best possible performance over the plungers (34) apart. entire speed range, the fuel injection pump is fitted with an automatic advance system, hydraulically Pumping and delivery process: actuacted (32). It is pre-set at the factory. During further rotation of rotor (15), inlet passage (13) in the pump head is closed and The speed advance adjusts timing of the fuel injection discharge port (27) in the rotor eventually aligns with pump in relation to engine speed and load.
one of the outlet bores in the pump head. Meanwhile the pump plungers (34) have reached the cam so IMPORTANT: Remember that all adjustments to that they move towards each other. The trapped, the injection pump - except for slow metered fuel is forced, under high pressure, through idle - must be carried out on a test discharge port (27) in the rotor and outlet opening in bench by a specialist injection pump the pump head, through pressurizing valve and repair station only. Internal connected pressure line, to the fuel injection nozzle adjustments in the field are not and into the appropriate cylinder. permitted, as this pump is a sealed unit. CD,3274,G220,6 -19-01FEB94 220 7