PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 2/TASK 2
(b) The bushing bore is connected to the fuel supply by two funnel
shaped ports, one on each side at different heights. The plunger operates
up and down in the bushing bore.
(c) The plunger is actuated by a camshaft that is built right into
the engine. The operation takes place through a rocker arm and push rod.
The push rod has a rollertype cam follower and is spring loaded to prevent
component damage in the event of injector nozzle clogging. The plunger is
situated under a follower. This follower is springloaded to make it follow
(d) The plunger can be rotated in operation around its axis by the
gear, which is meshed to the control rack. Each injector rack is connected
by an easily detachable joint to a lever on a common control tube which, in
turn, is linked to the governor and the throttle.
(e) For metering purposes, a recess with an upper helix and a
lower helix, or a straight cutoff, is machined into the lower end of the
plunger. The relation of this upper helix and lower cutoff to the two ports
changes with the rotation of the plunger. As the plunger moves downward,
the fuel in the highpressure cylinder or bushing is first displaced through
the ports back into the supply chamber until the lower edge of the plunger
closes the lower port. The remaining oil is then forced upward through the
center passage in the plunger into the recess between the upper helix and
the lower cutoff, from which it can flow back into the supply chamber until
the helix closes the upper port. The rotation of the plunger, by movement
of the rack, changes the position of the helix in relation to the ports.
This will advance or retard the closing of the ports and the beginning and
ending of the injection period. This will result in a regulation of the
volume of the fuel charge that is injected into the cylinder.
(f) When the control rack is pulled out completely, the upper port
is not closed by the helix until after the lower port is uncovered. This
means that all the fuel in the highpressure cylinder bypasses back to the