Textron JACOBSEN GP400, Technical/Repair Manual

Page: 71 / 354

ELECTRICAL
4252490-Rev A 4-19
4
Gasoline Engine Circuit—Theory of
Operation
Power Circuit
When the key switch is turned to the run position, voltage
is provided from key switch terminal B to control module
terminals J1-2, J2-11, and J2-12, powering up the control
module.
Switched power is also provided to the fuel pump. With
switched power provided to the fuel pump, the fuel pump
starts to operate. (See “Power Circuit—Theory of
Operation” on page 4-14.)
Interlock Circuit
To start and operate the engine, the following must
occur:
• Seat switch in the on position (operator on seat)
• Park brake switch in the on position
• Mow switch in the off position
When the seat switch is in the on position, voltage is
provided to the control module seat switch input terminal
J1-7, activating the input.
When the park brake switch is in the on position, voltage
is provided to the control module park brake switch input
terminal J1-11, activating the input.
When the mow switch is placed in the off position,
voltage is not provided from the switch to the control
module mow switch input terminal J1-5, indicating the
switch is in the off position.
Start Circuit
When the key switch is turned to the start position,
voltage is provided from key switch terminal C to the
control module start input terminal J1-6, activating the
input.
With the start input activated, the control module start
relay output terminal J2-4 provides voltage to start relay
terminal 86, energizing the relay. With the start relay
energized, voltage is switched between relay terminals
30 and 87 and provided 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.
At the same time, the control module engine run output
terminal J2-5 provides voltage to the carb solenoid,
energizing the solenoid. With the solenoid energized, the
carb solenoid plunger retracts, allowing fuel to flow.
The control module engine run output terminal J2-5 also
provides voltage to engine stop relay terminal 86, which
energizes the relay. With the engine stop relay
energized, the relay un-grounds the ignition modules,
allowing the modules to produce spark when the engine
is turning.
The control module engine run output terminal also
provides voltage to the hour meter, and the hour meter
starts logging hours.
Run Circuit
When the operator is on the seat (seat switch in the on
position), the control module allows the engine to
continue to operate when the park brake switch is in the
off position. The control module will deactivate the engine
run output terminal if the operator leaves the seat with
the park brake switch in the off position.
When the park brake is engaged (park brake switch in
the on position), the control module allows the engine to
continue to operate when the operator is off the seat. The
control module will deactivate the engine run output
terminal if the park brake is disengaged with the operator
off the seat.
When the control module deactivates the engine run
output terminal, voltage is no longer provided to the carb
solenoid and the carb solenoid plunger extends, stopping
fuel flow.
At the same time, the engine stop relay de-energizes and
relay terminal 87A provides a ground to the ignition
modules, preventing the modules from producing spark.
Charging Circuit
The charging circuit is a permanent magnet and stator
design. As the flywheel turns, the magnets pass the
stator coils, producing AC voltage. The AC voltage is
rectified by the voltage regulator, and DC voltage is
produced. The DC voltage is used to charge the battery.
When the battery voltage is low, the voltage regulator
supplies regulated voltage to charge the battery. When
the battery is fully charged, the regulator stops providing
voltage to the battery.