PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 2/TASK 2
constant supply of low-pressure fuel from the delivery pump.
As with the
multiple unit injection system, delivery pump pressure is regulated to
approximately 15 psi.
(c) The triangular land serves to consecutively block each pump
delivery port as it rotates.
The triangular land is situated so that it
will block each pump delivery port at the same time that the wobble plate is
moving the respective pump plunger at the maximum speed through its delivery
stroke.
(d) The rotational relationship of the rotary valve and the wobble
plate causes each pump to deliver a fuel charge to its respective injector
in turn as the pump rotates. The pumps in the injection unit are connected
to the fuel injectors to coincide with the firing order of the engine. The
pump is gear driven by the engine at a speed of exactly one-half that of the
crankshaft. The end result will be the injection of fuel to each cylinder
at the beginning of each power stroke.
(e) To obtain zero delivery, the valve is moved endwise to a
position where the delivery ports are never blocked by the triangular land.
When this occurs, the movement of the pump plungers merely causes the fuel
to move back and forth in the delivery ports. This results in zero delivery
to the injectors due to insufficient pressure to open the spring-loaded
delivery valves.
(f) To cause the pump to deliver fuel, the rotary valve is moved
endwise so that the triangular land begins to block the delivery ports. Due
to the triangular shape of the land, further endwise movement of the rotary
valve will increase the time that the port is blocked, increasing fuel
delivery.
The end result is that fuel delivery can be controlled by the
endwise movement of the rotary valve. Endwise movement of the rotary valve
is accomplished by the control lever. The position of the control lever is
determined by the governor.
d. Distributor-Type Injection System.
(1) General System Operation (figure 47 on the following page). The
distributor injection system used in automotive diesel engines is classed as
a low-pressure system in that pumping, metering, and distribution operations
take place at low pressure. The high pressure required for injection
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