TROUBLESHOOTING THE HMMWV - OD1616 - LESSON 1/TASK 1
The pressure will build up in the fuel line and the pump chamber as
the fuel pump fills the fuel injection pump. As the pressure rises
to the desired level in the pump chamber, it will hold the diaphragm
down against the pressure of the diaphragm spring.
When this
happens, the rocker arm will just move up and down in the slotted
pull rod with no pumping action until the fuel line pressure drops
below the desired level. In this way, the fuel pump regulates fuel
line pressure.
The operating range of the pump depends on the
tension exerted by the diaphragm spring.
A vent hole is provided under the diaphragm to allow the pressure to
change in the lower chamber as the diaphragm flexes.
The pulsating
chamber, located above the pump chamber, uses a soft diaphragm and a
sealed chamber to cushion the pulsating action inherent to the
diaphragm-type pump.
An oil seal is provided to keep crankcase oil
from entering the lower chamber and leaking from the vent hole.
(3) Fuel/Water Separator.
Thorough and careful filtration is
necessary to keep diesel engines efficient.
Diesel fuels are more
viscous than gasoline and contain more gums and abrasive particles
that could cause premature wear of injection equipment.
The
abrasives may consist of material that is difficult to eliminate
during refining, or they may even enter the tank during careless
refueling. Whatever the source, it is imperative that every means be
provided to protect the system from abrasives.
The fuel filter/water separator is a dual element unit. One element
is used to remove sediment from the fuel, while the other element
separates and collects any water that has gotten into the fuel.
A
water drain is provided, so that the water that has been collected
can be periodically drained.
Since the vehicle uses a plastic fuel
tank, the water does not have to be drained as often as one would
think.
(4) Fuel Injection Pump. The fuel injection pump directs metered
fuel to the eight injector nozzles. The injector pump is mounted on
the top of the engine under the intake manifold.
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