TM 9-6115-730-24
0003
AUXILIARY FUEL SYSTEM
The auxiliary fuel system consists of an external fuel supply, a fuel hose, a 24 Vdc auxiliary fuel pump with
strainer and solenoid valve, fuel lines, and an auxiliary fuel pump relay. When the EMCP AUX FUEL switch is ON,
the auxiliary fuel pump can transfer fuel from an external fuel supply to the generator fuel tank. The fuel level float
in the fuel tank shuts off power to the auxiliary fuel pump via the auxiliary fuel pump relay when the TQG fuel tank
is full and reactivates the pump as the level drops. The fuel level indicator on the EMCP indicates the fuel level of
the fuel tank from the empty (E) to full (F).
ELECTRONIC UNIT INJECTOR FUEL SYSTEM
The engine uses an EUI in each cylinder. A solenoid on each injector controls the amount of fuel delivered by the
injector. An engine speed/timing sensor detects top dead center (TDC). All fuel injection is timed off the
occurrence of TDC. The ECM determines how much fuel is to be delivered based on the difference between
desired and actual speed. The ECM then sets the timing from TDC for each cylinder based on data received from
the coolant temperature sensor, inlet air manifold temperature, atmospheric pressure sensor, and turbocharger
outlet (boost) pressure sensor. The ECM adjusts timing and fuel delivery for best engine performance, fuel
economy, and white smoke control.
The EUI fuel system uses a mechanically actuated electronically controlled unit injector. All fuel systems for diesel
engines use a plunger and barrel to pump fuel under high pressure into the combustion chamber. Fuel is pumped
into the combustion chamber in precise amounts to control engine performance. The EUI uses a fuel injection
pump camshaft lobe to power the plunger.
Engine Control Module (ECM)
The ECM computer electronically controls engine performance. The ECM uses engine performance data
gathered by several sensors to make adjustments to the fuel delivery, injection pressure and injection timing. The
ECM contains programmed performance maps (software) to define horsepower, torque curves and rpm. This
software is commonly called the personality module. The ECM logs faults of engine performance. The ECM can
diagnose problems with itself and the sensors and sensed values input to the module. When a problem is
detected, a diagnostic code is generated and sent to the GSC where it is displayed. In most cases, the code is
also logged with the engine hour value indicating when the failure occurred. When diagnostic codes are
generated, they are referred to as active. They indicate a problem presently exists. These should be serviced first.
Diagnostic codes stored in memory are referred to as logged failures. The existence of a logged code does not
indicate a current failure. The failure may have occurred some time ago. The logged codes are useful when
troubleshooting an intermittent problem. Logged inactive codes require a generic password to clear as described
in WP 0004 and WP 0083. Codes not requiring a password are automatically deleted from memory after 100
engine operating hours.
Fuel Transfer Pump and Fuel Flow
The fuel supply and injection circuit (Figure 3) is a conventional design for unit injected engines. It uses a fixed-
clearance gear fuel transfer pump to deliver fuel from the fuel tank to the unit injectors. The fuel transfer pump is
driven by the lower accessory drive gear. Fuel is pulled from the fuel tank and through the fuel filter/water
separator into the pump. The pump incorporates a check valve to permit fuel flow around the gears for hand
priming. The pump has a pressure regulating valve to protect the system from extreme pressure. The excess fuel
flow provided by the fuel transfer pump cools and purges the air from the unit injectors. The fuel is pulled from the
tank through the fuel filter/water separator and then through a five micron fuel filter. A fuel priming pump is located
on the fuel filter base. If unit
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