(a) Engine water temperature safety switch.
tachometer drive. The overspeed switch is normally
This normally closed temperature sensing device will
open and closes if engine speed should exceed 2350
shut down the engine if engine coolant temperature
RPM. The overspeed switch is wired to the fuel injection
should reach 210 to 220F (99 to 104C). When the
pump energized-to-run solenoid.
temperature safety switch opens at this temperature, the
switch opens, the circuit is interrupted causing fuel to the
energized-to-run fuel injection pump solenoid circuit is
engine to be shut off. If overspeed should occur, the
interrupted causing fuel supply to be shut off to engine.
overspeed switch must be manually reset.
(b) Engine oil pressure saf ety switch. This
(e) Thermostatic safety switch. This normally
normally open pressure sensing device will shut down
closed temperature sensing device will shut down the
the engine, if engine oil pressure should drop below 4
engine if the compressed air/oil mixture being
pounds (1.8 KG). The oil pressure safety switch is wired
discharged from the compressor reaches 230 to 240F
to the fuel injection pump energized to-run solenoid.
(110 to 116C). The switch is wired to the fuel injection
When the pressure switch closes, this circuit is
pump energized-to-run solenoid. When switch opens,
interrupted causing fuel supply to the engine to be shut
the circuit is interrupted causing fuel to the engine to be
off. When starting, the safety pushbutton switch on the
instrument panel must be pressed to override this
(f) Fuel injection pump solenoid. The fuel
injection pump incorporates an electrical shutoff,
(c) Air pressure safety switch. This normally
energized-to-run, solenoid. The circuit to the solenoid is
closed pressure sensing device is wired in series
energized when ignition switch on instrument panel is
between starting motor and starting pushbutton switch.
pulled to the ON position and de-energized when ignition
The air pressure safety switch opens at 10 PSI (0.7
is OFF. The injection pump circuit is also interrupted by
KG/CM2) and will prevent starting the engine if the
the safety devices incorporated in the unit, with
switch is open due to this pressure being in the air
exception of the air pressure safety switch. When the
safety devices interrupt the injection pump solenoid
circuit, spring action within the injection pump causes the
(d) Engine overspeed safety switch.
fuel metering valve to close. This action stops the flow
switch is an electronic type switch activated by a
of fuel to the injection nozzles and the engine will stop.