Komatsu PC88MR-10 Shop Manual page 252

10 Structure and function
Electrical control system
Accordingly, a fail-safe mechanism is provided, that is, the engine stops when the electrical system has
trouble.
When starting switch (6) is turned to "START" position while lock lever (9) is in "LOCK" position, the
starting current is supplied to starting motor (15) and the engine starts.
If lock lever (9) is in "FREE" position, starting motor cut-off relay (11) operates to cut off the starting current
to starting motor (15) and the engine does not start, that is, a neutral safety mechanism.
Upon receipt of the engine cut-off command from the external source, KOMTRAX terminal (19) sends the
signal to machine monitor (18).
Machine monitor (18) operates starting motor cut-off relay (12) to cut off the starting current to starting
motor (15), thus the engine does not start.
Engine speed control
Upon receipt of the throttle signals from fuel control dial (13) and pump controller (20), engine controller (8)
selects the lower throttle signal and sends the command current to fuel supply pump (16).
Fuel supply pump (16) adjusts the fuel injection rate to control the engine speed.
Stopping engine
When starting switch (6) is turned to "OFF" position, the current from ACC terminal of starting switch (6) to
engine controller (8) is cut off, and consequently the command current to fuel supply pump (16) is cut off.
Fuel supply pump (16) stops supplying fuel and the engine speed decreases to stop.
Stopping engine with engine shutdown secondary switch
If engine shutdown secondary switch (7) is turned to "Stop Engine" position, the current from the ACC
terminal of starting switch (6) to engine controller (8) is forcibly shut off.
Above induces the same state as when starting switch (6) is turned to "OFF" position, and the engine
stops.
Engine and pump combined control function
1. Battery disconnect switch
2. Battery
3. Battery relay
4. Fusible link
10-174
(PC88MR-C3W0-042-K-00-A)
PC88MR-10