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SSeeccttiioonn 55
EENNGGIINNEE DDCC CCOONNTTRROOLL SSYYSSTTEEMM
ENGINE CONTROLLER CIRCUIT BOARD
GENERAL:
The engine controller board is responsible for crank-
ing, startup, running and shutdown operations. The
board interconnects with other components of the DC
control system to turn them on and off at the proper
times. It is powered by fused 12 VDC power from the
unit battery.
CIRCUIT BOARD CONNECTIONS:
The circuit board mounts a 15-pin receptacle (J1) and
two single pin terminals (J2 and J3, see Figure 5.3).
Figure 5-2 shows the 15-pin receptacle (J1), the asso-
ciated wires and the function(s) of each pin and wire.
PPIINN WWIIRREE FFUUNNCCTTIIOONN
1 56 Delivers 12 VDC to Starter Contactor (SC)
while cranking only.
290
Delivers 12 VDC to Choke Solenoid coil
while cranking only. (Two seconds ON, Two
seconds OFF)
3 — Not used.
4 18A Grounds Magneto for Shutdown.
5 — Not used.
6 17 To Start-Stop switch. When wire is grounded
by setting Start-Stop switch to “START”,
engine will crank.
7 17 To Start-Stop switch on optional Remote
Panel.
8 — Not used.
9 4 Field Boost DC to Voltage Regulator and to
Rotor windings.
10 66 Starter Lockout. Prevents cranking while
engine is running.
11 85 Fault shutdown circuit. When grounded by clo-
sure of High Oil Temperature or Low Oil
Pressure Switch engine will shut down.
12 0 Common Ground.
13 16 12 VDC Input to Field Boost circuit while
cranking only.
14 18 To Start-Stop switch. When grounded by set-
ting Switch to “STOP” engine shuts down.
15 18
To Start-Stop Switch on optional Remote Panel.
Figure 5-2. – Receptacle J1
In addition to the 15-pin receptacle (J1), the circuit
board is equipped with two single pin terminals (J2
and J3). These terminals may be identified as follows:
1. Wire 14 connects to Terminal J2. During cranking and running,
the circuit board delivers battery voltage to the Wire 14 circuit
for the following functions:
a. To operate the electric Fuel Pump (FP).
b. To energize the Fuel Solenoid.
c. To operate the Choke Heater.
d. To the Remote Wire Harness to operate an
hourmeter or a light.
2. Wire 15 connects to Terminal J3. This is the power supply (12
VDC) for the circuit board and the DC control system.
Figure 5-3. – Engine Controller Circuit Board
BATTERY
RECOMMENDED BATTERY:
When anticipated ambient temperatures will be con-
sistently above 32° F. (0° C.), use a 12 volts automo-
tive type storage battery rated 70 amp-hours and
capable of delivering at least 400 cold cranking
amperes.
If ambient temperatures will be below 32° (0° C.), use
a 12 volt battery rated 95 amp-hours and having a
cold cranking capacity of 400 amperes.
BATTERY CABLES:
Use of battery cables that are too long or too small in
diameter will result in excessive voltage drop. For
best cold weather starting, voltage drop between the
battery and starter should not exceed 0.12 volt per
100 amperes of cranking current.
Select the battery cables based on total cable length
and prevailing ambient temperature. Generally, the
longer the cable and the colder the weather, the larg-
er the required cable diameter.
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