ARMY TM 9-6115-673-13&P
AIR FORCE TO 35C2-3-512-1
1.24.
LOW OIL PRESSURE PROTECTION.
1.24.1. The low oil pressure protection system (Figure 1-12) shuts down the diesel engine in the event of low oil
pressure in order to protect the engine from further damage. The system consists of a low oil pressure switch (S1)
located in the engine block above the oil strainer, a low oil pressure solenoid (L4) mounted in the control panel, and a
cable connecting the low oil pressure solenoid to the diesel engine STOP lever.
1.24.2 The generator control unit (A2) rectifies the alternating current supplied by the dynamo (G1) and provides
direct current via A2 pin VMAG+ to the low oil pressure solenoid (L4) at pin Y. The circuit is completed at A2 pin LOP
SOL which, after a short time delay, is allowed to pass through and exit A2 at pin LOP SW.
1.24.3. Under normal startup conditions, the low oil pressure switch (S1) opens at 12 to 18 psi (82.7 to 124.1 kPa) and
stays open as long as the engine oil pressure stays above 15 psi (103.4 kPa). If a malfunction occurs in the lubrication
system causing the oil pressure to drop below the low oil pressure set point, the low oil pressure switch (S1) closes.
The low oil pressure solenoid (L4) circuit terminating at A2 pin LOP SW becomes grounded when S1 closes. This
energizes the low oil pressure solenoid (L4) coil which momentarily pulls-in the solenoid's plunger. The plunger is
connected by a push-pull cable to the engine STOP lever. The cable trips the engine STOP lever placing the governor
control lever and the fuel injection pump rack in the "no fuel" position to cut off fuel to the diesel engine to shut down
the generator set.
LOW OIL
DIESEL
PRESSURE
ENGINE
SWITCH (S1)
GENERATOR
GOVERNOR
CONTROL
UNIT (A2)
LOW OIL
PRESSURE
STOP
SOLENOID
LEVER
(L4)
LEGEND
Mechanical
Electrical
