4-29. Engine Controls
4-30. Oil Pressure Switch
The automatic electrical shutdown system includes an oil
a. General. The oil pressure switch is located on the
pressure switch, a water temperature switch, a fuel
pressure switch and a shut down switch. The overspeed
left side of the engine above the by-pass oil filter (fig.
governor switch can be employed separately or in
conjunction with the electrical shut-down system. When
the engine is not running, the fuel oil pressure switch is
(1) Disconnect electrical wiring.
open, the lubrication oil pressure switch is closed and the
(2) Disconnect fuel oil tubing.
water temperature switch is open. After starting the
(3) Remove elbow, lock washers and hex nut
engine, the lubricating oil pressure switch contacts open
and remove switch.
when oil pressure reaches 10 psi, and the fuel oil
pressure switch contacts are closed when fuel oil
(1) Inspect for frayed or broken wiring.
pressure reaches 20 psi. The water temperature switch
(2) Check for cracks or breaks in switch housing.
is connected in parallel with the lubricating oil pressure
(3) Check connections and tubing for breaks,
switch and remains open unless coolant temperature
cracks or damage.
exceeds 200 + 5 F. The shut down solenoid would then
(4) Replace defective parts.
be energized. The overspeed governor switch activates if
d. Installation. Install the oil pressure switch in
engine speed exceeds the speed established by the
reverse order of removal.
engine governor causing the shut down solenoid to close
the shut down valve.
Figure 4-17. Oil pressure switch, removal and installation.