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TM 5-3805-296-23-1
FIELD MAINTENANCE
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THEORY OF OPERATION
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FUEL SYSTEM
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Engine Control
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The engine uses an electronic control module (ECM) which provides reference voltages to sensors and switches to
monitor engine and machine operating conditions. The engine ECM processes that information to adjust engine
controls for optimal engine operation. The engine ECM has a self-diagnostic capability which allows it to alert the
operator to any faults or out of range conditions. Fault codes can be retrieved by the electronic technician (ET) over
a data link.
Low Pressure Fuel Supply
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The low pressure fuel supply circuit supplies a constant supply of clean, air-free, pressurized fuel to the fuel mani-
fold on the cylinder head. Fuel is drawn from the fuel tank by an electronic fuel priming pump. The fuel priming
pump is part of the primary fuel filter base. The fuel priming pump evacuates air from the fuel and sends the fuel
through the primary fuel filter. The primary fuel filter removes large debris and water from the fuel. The fuel transfer
pump then draws fuel from the primary fuel filter and delivers it to the secondary fuel filter. The secondary fuel filter
removes small impurities from the fuel. The secondary fuel filter base is equipped with a fuel temperature sensor,
fuel pressure sensor, and a fuel pressure differential switch. The fuel temperature and fuel pressure are monitored
by the engine ECM. The fuel pressure differential switch actuates a warning light to inform the operator of a
restricted secondary fuel filter. The secondary fuel filter base also houses a fuel pressure regulating valve which
maintains a constant pressure. Excess fuel is returned to the fuel tank. Clean, air-free, pressure regulated fuel is
then supplied to the fuel manifold in the cylinder head.
Figure 1. Low Pressure Fuel Supply.
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