Figure 5-16. Pressure-Timed Injection System.
throughout the fuel system.
A pulsation damper
fuel to the injectors above maximum rated rpm. The
mounted to the gear pump contains a steel diaphragm
idle springs (in the governor spring pack) position the
that absorbs pulsations and smooths fuel flow through
governor plunger so the idle fuel port is opened enough
the fuel system.
From the gear pump, fuel flows
to permit passage of fuel to maintain engine idle speed.
through the filter screen to the governor screen. The
During operation between idle and maximum speeds,
PTG pumps are equipped with a bleed line that is
fuel flows through the governor to the injector in
attached to the engine injector return line or to the tank.
accordance with the engine requirements, as controlled
This prevents excessive fuel temperature within the fuel
by the throttle and limited by the size of the idle spring
pump by using the surplus fuel as a coolant. The bleed
plunger counterbore on the PTG fuel pumps. When the
line functions primarily when the pump throttle is set at
engine reaches governed speed, the governor weights
idle speed, but gear pump output is high due to engine
move the governor plunger, and fuel flow to the injectors
operating speed, as occurs during downhill operation. A
is restricted. At the same time, another passage opens
special check valve and/or fitting Is used in the gear
and dumps the fuel back into the main pump body. In
pump to accomplish the bleed action.
this manner, engine speed is controlled and limited by
the governor, regardless of throttle position.
(2) The governor controls the flow of the fuel
leaving the pump flows through the shutdown valve, inlet
from the gear pump, as well as the maximum and idle
supply lines, and into the injectors.
The mechanical governor is actuated by a
system of springs and weights and has two functions:
The throttle provides a means for the
First, the governor maintains sufficient fuel for idling with
the throttle control in idle position; second, it will restrict