Lesson 2/Learning Event 1
Distributor Injection System
This system, used in automotive diesel engines, is classed as a low-pressure system: Pumping, metering, and
distribution take place at low pressure. The high pressure required for injection is built up in the injector at
each cylinder. A suction gear pump lifts fuel from the tank and delivers it to the float chamber, from which
a second gear pump delivers it, at low pressure, to the distributor. Fuel passes through the distributor to the
metering pump, then through the distributor again, and on to the injector where it is injected into the
cylinder.
Distributor
The distributor consists of a rotating disk and a stationary cover which are connected to fuel lines running to
individual injectors. The disk and cover have a series of holes which, when properly indexed, form passages
from the fuel supply pump to the metering pump. The metering plunger moves down on its suction stroke
and permits the barrel to fill with oil. The disk continues to rotate and lines up with the correct discharge
hole in the cover just as the metering plunger rises by action of the main fuel pump cam. This forces the
fuel into the proper injector line.
Metering pump
The metering pump is a closely fitted reciprocating pump. Its motion is caused by a link from the plunger
lever. The plunger lever is operated by a vertical lever controlled, in turn, by an eccentric rocker lever
running directly off a cam on the fuel pump main shaft. The position of the vertical lever in the eccentric
of the rocker lever determines the travel of the plunger lever and, consequently, the travel of the metering
plunger.
As the metering plunger starts upward on its controlled stroke, it pushes fuel to the injector through passages
formed by the rotating distributor disk. The stroke of the metering plunger, which determines the amount
of fuel going to each injector, is varied by changing the position of the vertical lever between the stop pins in
the cam rocker lever.
Injector
The injector consists of a forged body with a fitted plunger. This plunger is forced down against spring
action by a rocker arm actuated by pushrods from the engine camshaft. Mounted on the end of the body is
the cup which contains the nozzle tip. On the
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