TROUBLESHOOTING THE HMMWV - OD1616 - LESSON 1/TASK 1
2.
Mechanical Systems
The HMMWV is made up of five mechanical systems.
In order for the
unit level mechanic to troubleshoot these systems, they must first
have an understanding of what the systems are, the components that
comprise each of these systems, and how these systems operate.
In the paragraphs that follow, we will cover each of these systems,
naming the system, listing the components, and stating how the system
operates.
3.
Engine
The engine used to power this family of vehicles is a four-stroke,
6.2 liter, V8, diesel engine.
The engine is a one-piece cast iron
block with overhead valves. The engine is governed at 3600 rpm with
a power output of approximately 150 horsepower. The normal operating
range of the engine is between 1500 and 2300 rpm.
There are six
subsystems that support the operation of the engine.
These
subsystems are: fuel, air, cooling, lubrication, electrical, and
a.
Ignition of the fuel in a diesel engine occurs
because of heat developed in the combustion chamber during the
compression stroke. Thus, no spark plugs or high voltage ignition is
necessary for a diesel engine.
However, fuel is required for
combustion; therefore, we will look at the fuel system and the travel
of fuel from the fuel tank to the point of combustion.
Fuel is pulled from the fuel tank by a mechanical fuel pump which is
located on the right side of the engine.
The primary fuel pump is
driven by a lobe on the camshaft through a push rod. The fuel, from
the fuel pump, travels to the fuel filter/water separator, which is
located on the body bulkhead above the engine. From the filter, the
fuel travels to the fuel injection pump where it is metered to the
injectors.
The injectors open at approximately 1960 psi, injection
pump pressure, and spray fuel into the combustion chamber of the
cylinder.
b.
Components of the Fuel System. In the preceding paragraphs the
flow of fuel, from the fuel tank to the combustion chamber, was
traced.
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