The time available for fuel to flow into the cup is deter-
mined by the time which the metering orifice in the barrel
is uncovered by the plunger. The metering orifice is un-
covered while the cam follower roller is on the inner base
circle of the cam. The plunger is in the retracted position
during this time. The amount of time the metering orifice
is uncovered is dependent on engine speed.
Injection of the fuel in the cup occurs when the cam
follower roller travels up the injection ramp of the cam
forcing the injector plunger downward. The end of injec-
tion occurs when the plunger bottoms in the cup.
The metering orifice is covered while the cam follower
roller is on the outer base circle of the cam. The plunger
is in the seated position during this time. Fuel supplied to
the injector during this time bypasses the plunger through
the drain port, and is returned to the fuel tank.
The engine will produce more horsepower at rated speed
than at torque peak; however, the engine will produce the
most torque at the torque peak speed. The rail pressure
is lower at torque peak speed, but the metering time is
greater, so more fuel is metered per cycle.
Fuel System General Information Section 5 - Fuel System
N14Page 5-6
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