TM 5-3805-294-10
OPERATOR MAINTENANCE
THEORY OF OPERATION
SCOPE
This section explains how components of the HYEX work together. A functional description is given for the engine,
Electronic Control Unit (ECU), fuel system, cooling system, electrical system, and hydraulic system.
Engine
The engine is a John Deere 6068H PowerTech Plus, 6.8L, 6-cylinder diesel engine. The 6068H includes a
turbocharger, electronic control unit, 4-valve per cylinder head, electronic fuel injectors, and a high-pressure common
rail fuel system. The 6068H is air-to-air after cooled to help reduce exhaust emissions while maintaining low-speed
torque. The engine application includes a hydraulically-driven cool-on-demand fan system.
ECU
The electronic control system serves as an engine governor, controlling the engine speed by delivering fuel, in
precise amounts, and at precise time according to a given set of engine conditions in relation to piston position. In
order to achieve this, the control system performs the following functions:
Constantly monitors engine operating conditions
Performs system diagnosis
Notify operator of machine faults through the monitor
Can derate or shut down engine to prevent damage
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