3-7.3.2 Shutoff systems. Four electrically operated shutoff systems function in the following manner during operation of
the generators. When a critical condition exists, a switch automatically doses the circuit to the shutoff solenoid. This
action stops fuel flow to the cylinders and shuts off the engine. The shutoff control either resets itself or must be reset by
a crewmember before the engine restarts. These shutoff systems are discussed in Paragraphs a through c below.
The temperature shutoff sensing element must be submerged in coolant to
operate. If coolant Is low, engine can overheat, and automatic shutoff will not
function to prevent damage to engine.
High water temperature shutoff switch is located in the water temperature regulator housing. When the water
temperature is too high, the solenoid fuel cutoff switch doses and the engine shuts off. When the engine stops,
switch the ECS or ENGINE START/STOP switch to STOP. This will prevent the temperature shutoff switch from
automatically restarting the engine when this switch resets after the coolant cools. Troubleshoot cooling system
and repair as necessary. Restart engine by following procedures in paragraphs 3-7.2 and 3-7.4.
Low oil pressure shutoff switch is on the side of engine with oil lines connecting to the switch. When the engine
oil pressure is too low, the solenoid fuel cutoff switch closes and shuts off the engine. When engine stops, switch
the ECS on ENGINE START/STOP switch to STOP. Troubleshoot lubricating system and repair as necessary.
Before restarting engine, reset oil pressure shutoff switch by pushing reset button until it latches. After engine
starts and develops oil pressure, pressure will push reset button to extended position. If button remains in reset
position, engine is not developing normal oil pressure. Troubleshoot and correct as necessary. Restart engine by
following procedures in paragraphs 3-7.2 and 3-7.4.
If the oil pressure shutoff switch reset button does not move to extended position
after engine is running, the shutoff switch Is not protecting the engine from low oil
pressure and may damage the engine.
Electronic overspeed shutoff switch protects the engine as follows:
· Sudden stopping of engine under load may be hazardous to systems in
operation being powered by an online generator set
· If engine overspeeds, stop It Immediately to prevent a runaway engine from
The electronic overspeed shutoff switch uses a magnetic pickup mounted in the flywheel housing to sense
engine speed. When the engine overspeeds, the magnetic pickup doses the circuit to the fuel shutoff
solenoid and stops the engine. When the engine stops, turn the ECS on ENGINE START/STOP switch to
STOP. Troubleshoot and repair as necessary. Reset over speed shutoff switch, either on engine
overspeed panel or on switchboard SSG panel. Restart engine by following procedures in paragraphs 3-
7.2 and 3-7.4.
The overspeed sensing device has a second sensing circuit that prevents the starter pinion from remaining
engaged in the flywheel at excessive rpm. After starter has cranked the engine, pinion gear may remain
engaged in flywheel as engine speed increases. At 600 rpm, the magnetic sensing device opens a circuit
to the starter and disengages pinion. This circuit remains open until flywheel stops. The open circuit
prevents starter from energizing while flywheel is turning. This safety device does not require resetting.