Isuzu AA-6HK1T, Workshop Manual

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6C–4 ENGINE FUEL
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Injection pump
Major injection pump components are the pump body,
the plungers, the governor, and the timing advancer.
The injection pump is the nucleus of the diesel engine
fuel system. It pressurizes and delivers precisely timed
and measured fuel charges to the engine cylinders.
Timing and volume are determined by engine load and
speed.
Each plunger is raised to the top of its stroke by a cam
lobe and forced to the bottom of its stroke by a return
spring.
Together, the plungers create a reciprocal motion.
Fuel enters the plunger barrel through the inlet port
when the plunger is at the bottom of its stroke.
Excess fuel leaves the plunger barrel through the outlet
port when the plunger is at the top of its stroke.
The injection pump has an identification tab attached to
its body.
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Governor
The fuel system uses an RSV variable speed governor.
Engine speed and load vary widely during normal
driving. If the engine speed is too low, the engine will be
sluggish and may stall. If engine speed is too high,
overrun occurs.
The governor operates to maintain engine speed within
acceptable limits thus preventing stalling and overrun.