Section 2 Engine DC Control System
20 Diagnostic Repair Manual
Circuit Condition - Start
With the start-run-stop switch (SW1) held in the START
position, wire 17 is internally closed to ground via wire 0.
By grounding wire 17, current is allowed to flow through
the SCR and energize the SCR coil. The SCR contacts
internally close wire 13 to wire 16.
Wire 16 then delivers battery voltage to the starter
contactor (SC) on the starter motor (SM). The SC is
energized and the contacts close, delivering battery
voltage to the starter motor and the engine will start
cranking.
With the start-run-stop switch (SW1) held in the START
position, wire 15 is connected to wire 167. Wire 15
supplies fused battery power via wire 167 to the printed
circuit board. This 12 VDC input signals the printed circuit
board to internally ground wire 229 which is connected to
the coil of the start stop relay (SSR). This action allows
current to flow and the SSR is energized. The normally
open contacts close supplying battery power from wire 15
to wire 14. Wire 14 supplies power to the fuel shutoff
solenoid (FSS).
The FSS is energized and fuel is available to the engine.
Wire 14 also supplies power through resistor (R1) and
diode (D1) to wire 4. Wire 4 connects to the field or the
rotor assembly and is used as field boost. The second
set of normally open contacts on the SSR also close
connecting wire 15 to wire 15B.
Wire 15B now supplies 12 VDC to the printed circuit
board for use with the governor control system. The
normally closed contacts now open, wire 18 is no longer
connected to wire 0 and the magnetos are no longer
grounded out, allowing voltage to flow to the spark plugs.
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