INTRODUCTION TO THE HMMWV - OD1615 - LESSON 1/TASK 2
d. Fuel/Water Separator. Thorough and careful filtration is especially
necessary to keep diesel engines efficient. Diesel fuels are more viscous
than gasoline and contain more gums and abrasive particles that may cause
premature wear of injection equipment.
The abrasives may consist of
material that is difficult to eliminate during refining, or they even may
enter the tank during careless refueling.
Whatever the source, it is
imperative that 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
Since the vehicle uses a plastic fuel tank, eliminating
condensation, the water does not have to be drained as often as one would
For proper engine performance, the fuel must be
injected into the combustion space in a definite spray pattern.
accomplished by the fuel injector.
The fuel enters the nozzle holder body through the high-pressure inlet. It
then passes down to the pressure chamber above the valve seat.
pressure developed by the injection pump exceeds the force exerted by the
pressure adjusting spring, the nozzle valve will be lifted off of its seat,
resulting in the injection of fuel into the cylinder.
The valve on the
HMMWV will open at approximately 1960 psi.
A controlled seepage exists between the lapped surfaces of the nozzle valve
and its body to provide for lubrication. This leakage or overflow passes
around the spindle and into the pressure adjusting spring chamber.
there, the lubricating fuel leaves the injector, through an overflow outlet,
to the overflow lines, which lead back to the low-pressure fuel supply.