TM 9-6115-730-24
0003
ENGINE SENSORS - Continued
Speed Input
The speed input signal to the ECM is a pulse width modulated control signal which eliminates the mechanical
throttle and governor linkages along with their adjustments. The nominal frequency is 500 200 Hz. The pulse
width varies from 10% to 90% corresponding to idle and maximum speed of the engine. Signals outside of this
range are considered a failure and a fault code is logged.
Fuel Temperature Sensor
Fuel temperature is monitored and used to adjust fuel rate calculations and for fuel temperature power correction.
When fuel temperature exceeds 86F (30C), fuel rates are corrected to provide consistent power. Maximum
power correction is achieved at 158F (70C). Fuel temperatures exceeding 176F (80C) for 30 seconds cause a
diagnostic code to be logged.
TDC Probe Input
A connector on the engine harness is used to calibrate engine timing. A special probe is inserted into the engine
and this extra connector is connected to the probe. This special probe is used to determine how long after the
speed/timing sensor(s) sense top dead center (TDC) it actually occurs. This data is programmed into the engine
ENGINE STARTING SYSTEM
The engine starting system (Figure 1) consists of four 12-volt batteries connected in series and parallel, a 24 Vdc
starter, a 24 Vdc battery charging alternator, a magnetic pickup (for sensing engine speed) and the related
switches and relays (described below) required for control of the starting system. The four 12 Vdc batteries are
configured in sets of two with each set consisting of two 12 Vdc batteries in parallel and the sets connected in
series to make a 24 Vdc system. The PUSH TO STOP EMERGENCY STOP pushbutton on the EMCP will
automatically disable the starting system and shut down the TQG if it is pushed in. For engine cranking, battery
power is supplied to the starter motor through the starter solenoid that in turn is controlled by the EMCP. The
starter engages the engine flywheel causing the engine to turn over. As the engine accelerates to above idle
speed (sensed by the magnetic pickup), the EMCP disengages the starter. Moving the ENGINE CONTROL switch
to COOL DOWN/STOP may also stop the starting sequence. The engine may be cranked without starting by
engaging the DEAD CRANK SWITCH. The DEAD CRANK SWITCH is a three-position switch. Up position is
CRANK, the center is OFF, and the lower position is NORMAL (operation). With the DEAD CRANK SWITCH in
CRANK, the starter motor is energized without activating any other starting or control function. With the switch in
the OFF center position, the system is off. With the switch in NORMAL (operation) position, the TQG may be
cranked and started. The belt-driven engine alternator charges the batteries. The battery charging alternator also
supplies GSC power. Normal operating indication depends on the state of charge in the batteries. A low charge,
such as exists immediately after engine starting, will cause a high reading. If the batteries are dead or inoperable,
external +24 Vdc power can be supplied to the TQG via the 24 Vdc NATO slave receptacle to start the generator
set engine. Cold outside temperatures make starting the engine difficult. The engine ECM controls the ether start
to improve the cold starting capability. The ether start is described in the Air Intake and Exhaust System
paragraph.
0003-3