Jacobsen Eclipse 322, Руководство по ремонту

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ELECTRICAL
4222983 Second Edition 4-31
4
Diesel Engine Circuit—Theory of
Operation
Power Circuit
Unswitched 48V power is available from stud 3 through
150A fuse (F8) and 0.02 ohm resistor (R6) to key switch
terminal A and liquid crystal display (LCD) terminal
J11-8.
When the key switch is turned to the run position, 48 volts
is provided from key switch terminal B to liquid crystal
display (LCD) ignition terminal J11-5, powering up the
LCD.
With the LCD powered up, a ground is provided from the
LCD switched power contactor output terminal J11-10 to
the power distribution unit (PDU) terminal J1-4. With a
ground provided to J1-4, the 12 and 48 volt switched
power contactors are energized.
With the PDU 12 volt switched power contactor
energized, 12 volts is provided through 0.02 ohm resistor
(R12) to the main control unit (MCU) 12 volt power input
terminal J2-8. PDU terminal J1-5 also provides 12 volts
to splice E and then from splice E, 12 volts is provided to
MCU 12 volt power input terminal J2-6. With the PDU 48
volt switched power contactor energized, 48 volts is
provided to circuit breaker (F4) and MCU 48 volt power
input terminal J2-7, powering up the MCU.
Glow Plug Circuit
With the MCU powered up, 12 volts is provided from the
MCU glow plug output terminal J2-3 to the PDU glow
plug relay terminal 86, energizing the relay. With the relay
energized, voltage is switched between relay terminals
30 and 87 and supplied to the glow plugs, heating the
glow plugs. At the same time the MCU instructs the LCD
display to turn on the glow plug light through the
controller area network (CAN).
Diode V5 conducts to ground the reverse voltage
generated when the glow plug relay is de-energized.
Glow plug timing is determined by the engine
temperature sensor input.
Start Circuit
When the key switch is turned to the start position, 48
volts is provided from key switch terminal C to the LCD
start input terminal J12-2, activating the input. The status
of the key switch is communicated between LCD and the
main control unit (MCU) through the controller area
network (CAN).
With the key switch (status) in the start position, 12 volts
is provided from the MCU fuel hold output terminal (J2-4)
to the fuel shutoff solenoid’s hold-in coil. Current also
momentarily flows from the MCU fuel pull-in output
terminal J2-5 to the fuel shutoff solenoid’s pull-in coil,
momentarily energizing the coil. With the pull-in coil
momentarily energized, the fuel shutoff solenoid plunger
retracts. The pull-in coil is a high-current winding and is
energized momentarily by the MCU to prevent damage.
The fuel shutoff solenoid hold-in coil keeps the plunger in
the retracted position.
The MCU start output terminal J2-2 provides12 volts to
start relay terminal 86, energizing the relay. With the start
relay energized, voltage is switched between relay
terminals 30 and 87 and supplied to the starter motor
solenoid, energizing the solenoid. With the starter
solenoid energized, voltage is switched between the
starter solenoid contacts to the starter motor, engaging
the motor. Diode V4 conducts to ground the reverse
voltage generated when the start relay is de-energized.
The MCU will only engage the starter for 10 seconds. If
the engine fails to start, the key switch must be turned to
the off position before attempting to start again.
Run Circuit
The engine continues to operate when the key switch is
in the run position.
If the engine oil pressure drops below 7 psi (1.72 bar) the
engine oil pressure switch closes.
With the engine oil pressure switch closed, a ground is
provided to the MCU oil pressure input terminal J3-7,
activating the input. With the oil pressure input activated
the MCU instructs the LCD to turn on the low oil pressure
light through the controller area network (CAN). After a
timed delay, the MCU will de-energize the fuel shutoff
solenoid’s hold-in coil, shutting off the engine.
The resistance of the engine temperature sensor
changes in relationship to temperature. The MCU engine
temperature input terminal J3-8, measures the resistance
of the engine temperature sensor. When the engine
temperature reaches 230° F (110° C), the MCU instructs
the LCD to turn on the engine over temperature light
through the controller area network (CAN). After a timed
delay, the MCU will de-energize the fuel shutoff
solenoid's hold-in coil, shutting off the engine.