0308684 JOHNSON SCREW,Plate

Always determine the cause of the engine shutdown. Make necessary repairs before attempting restarting the engine.
Air Shutoff Solenoid (If Equipped)
This optional solenoid is located on top of the engine in the air inlet system. When the solenoid is activated, the solenoid mechanically shuts off inlet air to the engine. The solenoid can only be activated by the overspeed switch or the emergency stop switch.Fuel Shutoff Solenoid
This solenoid is located on the governor or on the fuel injection pump. When the solenoid is activated, the solenoid moves the fuel rack (either directly or through the governor) to the Fuel Off position.Overspeed Shutoffs
Magnetic pickup (1), mounted in the flywheel housing (2).A magnetic pickup mounted in the flywheel housing senses the passage of the flywheel ring gear teeth. Should the engine speed increase above the overspeed setting of the Electronic Speed Switch (118 percent of rated engine speed), the magnetic pickup will sense the overspeed. The overspeed condition activates both the air (if equipped) and fuel shutoff solenoids.The shutoffs must be reset before the engine will restart. A reset button on the Electronic Speed Switch (in the junction box) must be pushed to open the overspeed switch. The air shutoff lever (at the top of the air inlet housing) must be manually reset.Oil Pressure Switches
Typical example of oil pressure switches, mounted in the rear of the junction box.An oil pressure switch has wires connected to the electrical system for alarm or shutoff functions. The oil pressure switch senses oil pressure at the bearing oil gallery. If sufficient oil pressure is not achieved after engine starting, or if the engine has been running normally and then loses oil pressure, the fuel shutoff solenoid is energized to shut the engine off. No resetting procedure is required.Engine Step Oil Pressure
This is an adjustable engine speed setting that protects the engine from a failure caused by too little oil pressure for a specified speed range. This option requires two different oil pressure switches. One switch has a high pressure rating- when the engine is running above the speed setting, the engine must maintain oil pressure higher than the switch rating. The other switch has a low pressure rating- an engine running below the speed setting must maintain oil pressure above the low switch rating.In an automatic start/stop system, an automatic reset switch is used. Manually operated systems require the switch to be reset before the engine will start.
If the RESET button does not move to the extended position after the engine starts, the engine will NOT be protected by this particular switch.If the RESET button remains in the reset position, the engine oil pump will not develop normal oil pressure. An inspection should be made to correct the problem.
In order to reset the switch, push the RESET button until the button latches. After the engine starts and develops oil pressure, the button will move to the extended (running) position.
The button must be in the RUN position to protect the engine. If the button remains in the OFF position, the engine oil pump may not be developing normal oil pressure and proper checks should be made.
Water Temperature Contactor Switch
The water temperature contactor switch is located in the cylinder head. High water temperature closes the switch to activate an alarm or fuel shutoff. No resetting is required. The switch opens as the coolant cools.
The sensing element must be submerged in the coolant to operate. Be sure to have an adequate water supply in the jacket water system, or engine damage could result.
Shutoff and Alarm System Testing
Most control panels are equipped with a test switch. Turn the switch to ON position to check indicator lights for proper operation. Replace defective or burnt bulbs immediately.The engine protective devices should be tested every 1000 service hours or twice a year by authorized Caterpillar service personnel or other experienced, qualified mechanics.
During testing, abnormal operating conditions must be simulated. Perform the tests correctly to prevent possible damage to the engine.
Abnormal operating conditions must be simulated which could cause engine damage if the tests are performed incorrectly. Refer to the Service Manual for the testing procedures.Overspeed Switch Testing
The Electronic Overspeed Switch (if equipped) is located inside the junction box.The Electronic Overspeed Switch with Cranking Termination has a 75 percent VERIFY button, a RESET button, and an OVERSPEED indicator light.The Electronic Overspeed Shutoff Switch with Crank Termination has a sensing circuit which prevents the starter pinion from remaining engaged in the flywheel at excessive rpm. Crank Termination has an adjustable engine speed setting, and signals the starter motor when the engine is firing and cranking must be terminated. When the speed setting is reached, a switch opens to start the engine hour meter.After the starting motor cranks the engine, the pinion gear can remain engaged with the flywheel as the en