0316386 JOHNSON CLAMP

Introduction
The electric protective system is designed to activate an alarm or shut the engine off if there is a problem or a failure in any of five different engine systems. The engine systems monitored are: engine overspeed, starter motor crank terminate, engine reversal, engine oil pressure and engine coolant temperature.The electric protective system consists of the basic components that follow: tachometer speed sensor, electronic speed switch, water temperature contractor switch, two time delay relays and two slave relays. This system monitors the engine from starting through rated speed.Component Description
Tachometer Speed Sensor (TSS) - The sensor generates a signal that measures engine speed, but also has a special characteristic that sends the signal in a certain sequence. If the direction of rotation is changed, the signal sequence is changed. Electronic Speed Switch (ESS) - The speed switch has controls (in a single unit) to monitor four of the basic functions. These four functions are: Engine Overspeed - An adjustable engine speed setting (normally 118% of rated speed) that gives protection to the engine from damage if the engine runs too fast. This condition will cause a switch to close that shuts off both the inlet air and the fuel to the engine. Crank Terminate (Starter Motors) - An adjustable engine speed setting that gives protection to the starter motor from damage by overspeed. This condition will cause a switch to open that stops current flow to starter motor circuit, and the starter motor pinion gear will then disengage from engine flywheel ring gear. Engine Reversal - A condition where the engine starts to run backwards. This will cause a change in the signal from the TSS, which will close a switch to cause the fuel to be shut off to the engine. Engine Step Oil Pressure - An adjustable engine speed setting that gives protection to the engine from a failure caused by not enough oil pressure. To maintain desired protection through the complete speed range of engine operation, two different oil pressure switches are used [280 kPa (40 psi), 140 kPa (20 psi)]. Once the step oil pressure speed setting is made, an engine that runs above this speed setting must maintain an oil pressure that is more than 280 kPa (40 psi). An engine that runs at a speed below this speed setting must maintain an oil pressure that is more than 140 kPa (20 psi). If either condition is not correct, a switch will close and cause the fuel to be shut off to the engine. Water Temperature Contactor Switch - This contactor switch is a separate unit (mounted in the regulator housing) that is wired into the shutdown circuit. It has an element that feels the temperature of the coolant (it must be in contact with the coolant). When the engine coolant temperature becomes too high, the switch closes to cause the fuel to be shut off to the engine. Time Delay Relays - These relays are special ON/OFF switches with two controls that will either make the relay activate immediately, or after a 9 second delay. One of the time delay relays is used to arm the shutdown system, and the other time delay relay controls the oil pressure circuits for the two oil pressure switches. Both time delay relays have a 70 second OFF delay to be sure of complete engine shutdown. Slave Relays - These are standard type relays that, when energized, have contacts that open across one circuit and close across another circuit. When activated, one of the relays causes the fuel to be shut off, and the other relay causes the inlet air to be shut off.Component Locations On Engine
WATER TEMPERATURE CONTACTOR SWITCH
1. Regulator housing. 2. Contactor switch.
TACHOMETER SPEED SENSOR (TSS)
1. Tachometer speed sensor. 2. Service meter. 3. Tachometer drive housing.
JUNCTION BOX OPENED
1. Terminal strips. 2. Electronic speed switch (ESS). 3. Slave relays. 4. Time delay relays. 5. Oil pressure switches. 6. Circuit breakers.
AIR SHUTOFF SOLENOID
1. Air shutoff housing. 2. Air shutoff solenoid. 3. Aftercooler housing.
JUNCTION BOX CLOSED
1. Junction box. 2. Fuel shutoff switch. 3. Circuit breakers. 4. Magnetic pickup. 5. Electric governor actuator (EGA).
LEFT SIDE OF ENGINE
1. Enclosure group.Individual Circuit Description
The information that follows show the current flow through the wiring schematic. As switches are opened or closed, either automatically or manually, the current flow of the individual circuit affected is shown schematically.Also included (on each facing page) is a story that explains all the components involved for this particular condition, and why the current will take the path shown.Engine Stopped (Fig. 1)
With the engine stopped, power is always available across terminals 3 and 4 of time delay relays (TD1 and TD2) and across terminals 5 and 6 of electronic speed switch (ESS). At this time all switches are in their normally open or normally closed positions.Engine Stopped
Fig. 1Manual Start
Electric Starter Motors (Fig. 2)
When the start pushbutton (PB) or remote start switch (RSS) is pushed, current will flow through starter motor magnetic switches (SMMS1 and SMMS2). With magnetic switches energized, contacts (SMMS1 and SMMS2) close and pinion solenoids (PS1 and PS2) to close, and starter motors (SM1 and SM2) will now crank the engine. When engine starts to run and the rpm increases to the speed of the crank terminate (CT) speed setting, the ESS(CT) switch will automatically open across terminals ESS-11 and ESS-12 to stop current flow to the starter motors.Air Starter Motor (Current Flow Not Shown in Fig. 2)
If engine has an air starter motor, current will flow through DC operated air start solenoid valve (ASSV) when start pushbutton (PB or RSS) is pushed. The ASSV will open the air supply to the air starter motor, which will now crank the engine. When the engine starts to run and the rpm increases to the speed of the crank terminate (CT) speed setting, ESS(CT) switch will automatically open across terminals ESS-11 and ESS-12 to stop current flow to ASSV. This will move the valve to shut off the air supply to the starter motor.Starting Engine With Electric Starter