Systems Operation

Usage:

Introduction

NOTE: For Specifications with illustrations, make reference to Specifications for 3406C Industrial & Marine Engine Attachments, SENR6527. If the Specifications in SENR6527 are not the same as in the Systems Operation, Testing & Adjusting, look at the printing date on the cover of each book. Use the Specifications given in the book with the latest date.

Wiring Diagrams

Many types of electrical systems are available for these engines. Some charging systems use an alternator and a regulator in the wiring circuit. Others have the regulator inside the alternator.

A fuel or oil pressure switch is used in all systems with an external regulator. The switch prevents current discharge (field excitation) to alternator from the battery when the engine is not in operation. In the systems where the regulator is part of the alternator, the transistor circuit prevents current discharge to the alternator and the fuel or oil pressure switch is not required.

All wiring schematics are usable with 12, 24, 30 or 32 volts unless the title gives a specific description.

NOTE: Wire and cable shown dotted on wiring diagrams is to be supplied by customer. The charts that follow gives the correct wire sizes and color codes. The abbreviations given below are used with the wiring diagrams in this section.

The present type of wire identification, used on all Caterpillar equipment uses only eleven solid colors.

In addition to only eleven basic colors of wire, a circuit number is stamped (put) on each wire. The circuit number is stamped approximately every inch for the length of the wire. The identification number for a circuit will be the same for any Caterpillar equipment.

For example: A color code of "A701-GY" on the schematic would mean, there is a gray wire with the circuit number "A701" stamped on it. This wire is the solenoid signal wire (power) for cylinder #1 (CYLINDER HEAD SOL 1) on the Electronic Unit Injector (EUI) system wire harness. The "A701-GY" color code will be the identification of "SOLENOID 1 POWER" circuit on all Caterpillar equipment wire harnesses with Electronic Unit Injector (EUI) systems.

Another wire identification on the schematic is the size of the wire. The size or gauge of the wire is called "AWG". The gauge of the wire will follow the wire color.

For example: A color code of "150-OR-14" on the schematic would indicate the "150-OR" wire is a 14 AWG wire.

If the gauge of wire is not listed after the wire color, the gauge of the wire will be 16 AWG.

Grounded Electrical Systems

These systems are used in applications when it is not necessary to prevent radio distortion and/or chemical changes (electrolysis) of grounded components

Regulator Inside Alternator

Charging System
(1) Ammeter. (2) Alternator. (3) Battery.

Charging System with Electric Starting Motor
(1) Start switch. (2) Ammeter. (3) Alternator. (4) Battery. (5) Starting motor.

Regulator Separate From Alternator

Charging System
(1) Ammeter. (2) Regulator. (3) Pressure switch (N/O). (4) Resistor (used with 30 and 32V systems). (5) Battery. (6) Alternator.

Charging System with Electric Starting Motor
(1) Start switch. (2) Ammeter. (3) Regulator. (4) Resistor (for 30 and 32V systems). (5) Battery. (6) Starting motor. (7) Pressure switch (N/O). (8) Alternator.

Alternator-Off Engine

The following diagrams are for use only when an alternator or charging generator is not used in the engine electrical system.

System with One Starting Motor
(1) Start switch. (2) Starting motor. (3) Battery.

Insulated Electrical Systems

These systems are most often used in applications where radio interference is not desired or where conditions are such that grounded components will have corrosion from chemical change (electrolysis).

Regulator Inside Alternator

Charging System
(1) Ammeter. (2) Alternator. (3) Battery.

Charging System with Electric Starting Motor
(1) Start switch. (2) Ammeter. (3) Alternator. (4) Battery. (5) Starting motor.

Regulator Separate From Alternator

Charging System
(1) Ammeter. (2) Regulator. (3) Pressure switch (N/O). (4) Resistor (used with 30V and 32V systems). (5) Battery. (6) Alternator.

Alternator-Off Engine

The following diagrams are for use only when an alternator or charging generator is not used in the engine electrical system.

System with One Starting Motor
(1) Start switch. (2) Starting motor. (3) Battery.

Electric Tachometer Wiring

(1) Magnetic pickup. (2) Terminal Connections - terminals 18 and 19 on load sharing governor control and terminals 7 and 8 on standby governor control. (3) Tachometer. (4) Ground connection - governor control chassis ground. (5) Governor control terminal strip. (6) Wiring connections - for second tachometer circuit if needed. (7) All wire must be 22AWG shielded cable or larger. (8) Dual speed switch terminal strip. (9) Ground connection - ground to engine.

Automatic Start/Stop System - Non-Package Generator Sets

Automatic Start/Stop System Schematic (Hydraulic Governor)
(1) Starting motor and solenoid. (2) Shutoff solenoid. (3) Fuel pressure switch. (4) Water temperature switch. (5) Oil pressure switch. (6) Overspeed contactor. (7) Battery. (8) Low lubricating oil pressure light (OPL). (9) Overcrank light (CL). (10) Overspeed light (OSL). (11) High water temperature light (WTL). (12) Automatic control switch (ACS).

Automatic Start/Stop System Schematic (2301A Control System)
(1) Magnetic pickup. (2) Starting motor and solenoid. (4) Oil pressure switch 1 (OPS1). (5) Water temperature switch. (7) Overspeed switch. (8) Battery. (9) Low lubricating oil pressure light (OPL). (10) Overcrank light (OCL). (11) Overspeed light (OSL). (12) High water temperature light (WTL). (13) Automatic control switch (ACS). (14) EG-3P Actuator. (15) 2301A Control Box. (16) Oil pressure switch 2 (OPS2).

An automatic start/stop system is used when a standby electric set has to give power to a system if the normal (commercial) power supply has a failure. There are three main sections in the system. They are: the automatic transfer switch, the start/stop control panel (part of switch gear) and the electric set.

Automatic Transfer Switch

Automatic Transfer Switch (ATS)
(1) E1, E2, and E3 input to ATS from emergency source. (2) N1, N2 and N3 input to ATS from normal source. (3) T1, T2 and T3 output from ATS to the load. (4) Transfer mechanism.

The automatic transfer switch normally connects the 3-phase normal (commercial) power supply to the load. When the commercial power supply has a failure the switch will transfer the load to the standby electric set. The transfer switch will not transfer the load from commercial to emergency power until the emergency power gets to the rate voltage and frequency. The reason for this is, the solenoid that causes the transfer of power operates on the voltage from the standby electric set. When the normal power returns to he rated voltage and frequency and the time delay (if so equipped) is over, the transfer switch will return the load to the normal power supply.

Control Panel

Automatic Start/Stop Control Panel
(1) Overcrank light (OCL). (2) Low lubricating oil pressure light (OPL). (3) Overspeed light (OSL). (4) Automatic control switch (ACS). (5) High water temperature light (WTL).

The main function of the control panel is to control the start and shutoff of the engine.

The engine control on the automatic start/stop control panel is an automatic control switch (ACS) with four positions. The positions of automatic control switch (4) are: OFF/RESET, AUTO, MAN and STOP. Each light (1), (2), (3) and (5) goes ON only when a not normal condition in the engine stops the engine. The light for the condition in the engine that stopped the engine ON even after the engine has stopped. Automatic control switch (4) must be moved to the OFF/RESET position for the light to go OFF. Each light will go ON, for a light test, when the light is pushed in and held in.

When the generator is to be used as a standby electric power unit, the automatic control switch is put in the AUTO position. Now, if the normal (commercial) electric power stops, the engine starts and the generator takes the electric load automatically. When the normal (commercial) electric power is ON again, for the electric load, the circuit breaker for the generator electric power automatically opens and the generator goes off the electric load. After the circuit breaker for the generator opens, the engine automatically stops.

When the automatic control switch (ACS) is moved to the MAN position, the engine starts. It is now necessary for the circuit breaker for the generator electric power to be closed manually. If the generator is a standby electric power unit and the automatic control switch (ACS) is in the MAN position when normal (commercial) electric power is ON again, the generator circuit breaker opens and the engine stops automatically the same as when the switch (ACS) is in the AUTO position.

The engine will stop with the automatic control switch (ACS) in either the AUTO or MAN positions if there is a not normal condition in the engine. The not normal condition in the engine that can stop the engine is either low lubricating oil pressure, high engine coolant (water) temperature or engine overspeed (too much rpm). When any of these conditions stops the engine, the light for the not normal condition will stay ON after the engine is stopped. The fourth not normal condition light is ON only when the starting motor runs the amount of seconds for the overcrank timer (engine does not start).

Move the automatic control switch (ACS) to the OFF/RESET position and the not normal condition lights go OFF.

Electric Set

The components of the electric set are: the engine, the generator, the starting motor, the batter, the shutoff solenoid and signal switches on the engine. The electric set gives emergency power to drive the load.

An explanation of each of the signal components is given in separate topics.

Wiring Diagrams

The following wiring diagrams are complete to show the connections of the automatic start/stop components with the engine terminal strip (TSI). The diagrams show all available options for both the hydraulic governor application and the 2301A Control System application.

For a more complete explanation of operation of the automatic start/stop system, refer to Floor Standing Switchgear SENR7970.

Automatic Start/Stop Wiring

Component Abbreviations

A-DC: Ammeter
ACS: Engine Control Switch
ALT: Charging Alternator
AR: Arming Relay
ARX: Auxiliary Relay
ASO: Air Shutoff Solenoid
CB: Circuit Breaker
CCM: Cycle Cranking Module
CCT: Cycle Crank Relay
CDT: Cool Down Timer
CDTR: Cool Down Timer Relay
CRC: Cycle Crank Logic Timer
CTS: Crank Terminate Switch
DSS: Dual Speed Switch (Includes CTS And OSS)
GS: Governor Switch
GSM: Governor Synchronizing Motor
I: Initiate Contact (Remote Start)
MS: Magnetic Switch (Crank Circuit)
OCR: Overcrank Relay
OCT: Overcrank Timer
OP: Oil Pressure Indicator Sender
OPG: Oil Pressure Indicator
OPR: Low Oil Pressure Relay
OPS: Oil Pressure Switch
OPT: Optional Equipment
OSR: Overspeed Relay (In DSS)
PIL: Panel Illumination Lamp
PLS: Panel Lamp Switch
PS: Pinion Solenoid
RR: Run Relay
SS: Shutoff Solenoid
SM: Starting Motor
TDR: Time Delay Relay
TDX: Time Delay Auxiliary Relay
WT: Water Temperature Indicator Sender
WTG: Water Temperature Indicator
WTR: High Water Temperature Relay
WTS: Water Temperature Switch
*: Indicates Equipment External To Control Panel
0: Terminal Strip Point (Control Panel)
[ ]: Terminal Strip Point (Generator Terminal Box)
[]: Relay Contact Line Number

Control Panel Wiring Schematic

NOTE A: Terminals 13 and 14 of the generator box will be connected to terminals 13 and 14 of the control panel when the CDT is not supplied.

Note B: Red jumper wire from terminal strip point number 4A to 4 in control panel must be removed when the cycle cranking module (CCM) is used.

NOTE C: Auxiliary relay (ARX) contacts are to be customer wired. See Relay Contact Schematic.

NOTE D: Dotted lines shown on Control Panel Wiring Schematic show engine wiring.

NOTE E: The overcrank timer (OCT) is to be adjusted to the 30 second setpoint (red dot). When cycle cranking (CCM) is used the overcrank timer (OCT) is to be adjusted to the 90 second setpoint (white dot).

NOTE F: ACS switch contacts shown with switch in auto position.

NOTE G: Jumper wire from terminal 72 to terminal 73 must be removed when DC ammeter (A) is used.

NOTE H: Jumper wire from terminal 13 to terminal 133 to be removed if additional fault shutdowns are added. Examples: reverse power relay or remote shutdown. Insert a normally closed switch between terminal 13 and terminal 133.

Automatic Start/Stop Wiring For Non-Package Generator Set

Used with Hydra Mechanical Governors

For wire sizes and color codes see the chart at the front of Wiring Diagrams section.

Wires and cables show in dotted lines are customer supplied wiring.

Starting System with One Starting Motor
(1) Magnetic switch. (2) Circuit breaker. (3) Starting motor. (4) Battery. (5) Circuit breaker. (6) Terminal strip (on engine).

Dual Speed Switch
(7) Magnetic pickup. (8) Dual speed switch. (9) Time delay relay. (10) Oil pressure switch. (11) Governor synchronizing motor. (12) Water temperature switch.

Shutoff Solenoids
(13) Circuit breaker. (14) Rack shutoff solenoids. (15) Diode.

Automatic Start/Stop System Schematic

Automatic Start/Stop Wiring For Non-Package Generator Set

For wire sizes and color codes see the chart at the front of Wiring Diagrams section.

Wires and cables show in dotted lines are customer supplied wiring.

Starting System With One Starting motor
(1) Magnetic switch. (2) Circuit breaker. (3) Starting motor. (4) Battery. (5) Circuit breaker. (6) Terminal strip.

System Components
(7) Oil pressure contactor. (8) Dual speed switch. (9) Governor actuator. (10) Time delay relay. (11) Magnetic pickup. (12) Oil pressure switch. (13) Water temperature switch.

NOTE A: For standby operation - magnetic pickup (MP) and oil pressure contactor must be wired to governor control with two conductor shielded cable (Beldon Mfg. Co. type 8780 or equivalent). (MP) should be connected to terminals 7 and 8 on governor control assembly and oil pressure contactor should be connected to terminals 9 and 10 on governor control assembly. Shields should be grounded at governor control grounding stud. Individual shields should not have multiple ground connections. Magnetic pickup from governor control assembly is not needed. Use magnetic pickup from speed switch group. Wire from magnetic pickup to (DDS). Then wire from (DDS) to governor control assembly using to conductor shielded cable - terminal 4 on (DDS) to terminal 8 on governor control assembly, terminal 3 on (DDS) to terminal 7 on governor control assembly. Remove (MP) shield from terminal 2 on (DDS) and connect to shield on governor cable, ground the shield at the governor control assembly ground stud. The (DDS) may be installed physically near the governor control assembly if desired.

NOTE B: For load sharing operation - magnetic pickup (MP) and oil pressure contactor must be wired to governor control with two conductor shielded cable (Beldon Mfg. Co. type 8780 or equivalent). (MP) should be connected to terminals 18 and 19 on governor control assembly and oil pressure contactor should be connected to terminals 14 and 15 on governor control assembly. Shields should be grounded at governor control assembly grounding stud. Individual shields should not have multiple ground connections. Magnetic pickup (MP) from governor control assembly is not needed. Use (MP) from speed switch group. Wire from (MP) to (DDS). Then wire from (DDS) to governor control assembly using two conductor shielded cable - terminal 4 on (DDS) to terminal 19 on governor control assembly, terminal 3 on (DDS) to terminal 18 on governor control assembly. Remove (MP) shield from terminal 2 (DDS) and connect to shield on governor cable. Ground the shield at the governor control assembly grounding stud. The (DDS) may be installed physically near the governor control assembly if desired.

Automatic Start/Stop System Schematic

Electric Shutoff And Alarm Systems

Introduction

There are three types of electrical protection systems available for the 3406C Engines.

1. Water Temperature and Oil Pressure Protection.

2. Water Temperature, Oil Pressure and Overspeed Protection.

3. Automatic Start Stop Systems for Non-Package Generator Sets.

The electric shutoff system is designed to give protection to the engine if there is a problem or a failure in any of the different engine systems. The engine systems that are monitored are: engine overspeed, starting motor crank terminate, engine oil pressure and engine coolant temperature.

The electric protection system consists of the electronic speed switch and time delay relay. This system monitors the engine from starting through rated speed.

Dual Speed Switch (DDS)

The speed switch has controls (in a single unit) to monitor engine overspeed and crank terminate speed.

Engine Overspeed

An adjustable engine speed setting (normally 118 percent 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 the fuel to the engine.

Crank Terminate (Starting Motor)

An adjustable engine speed setting that gives protection to the starting motor from damage by overspeed. This condition will cause a switch to open that stops current flow to starting motor circuit, and the starting motor pinion gear will then disengage from engine flywheel ring gear. The crank terminate can also be used to activate the time delay relay.

Time Delay Relay

This relay has special ON/OFF switches with two controls that will either make the relay activate immediately, or after a nine second delay. The time delay relay is used to arm the shutdown system. The time delay relay has a 70 second delay to be sure of complete engine shutdown.

Water Temperature Contactor Switch

This contactor switch is a separate unit that is wired into the shutdown circuit. It has an element that feels the temperature of the coolant (it must be in contact with he coolant). When the engine coolant temperature becomes too high, the switch closes to cause the fuel to be shut off to the engine. The switch is installed in the top front of the cylinder head.

Engine Oil Pressure Switch

This switch is installed in the main oil gallery on the right side of the cylinder block. The oil pressure switch is used to determine low engine oil pressure and to activate the time delay relay.

Wiring Diagrams

Abbreviations, wire codes and recommended wire sizes, used with the wiring diagrams that follow, can be found at the front of the Wiring Diagrams Section.

The notes that follow are used with the wiring diagrams shown in this section.

NOTE: Customer to Furnish Battery and All Wires Shown Dotted

NOTE A: Optional ground to engine may be used with grounded systems only.

NOTE B: These leads terminate at the starting motor and must be omitted when there is no starting motor and must be omitted when there is no starting motor. In this case customer must provide DC power at the other termination point of these two leads.

NOTE C: If 2301A Governor is used, only one magnetic pickup is required. Use magnetic pickup from overspeed group. Wire magnetic pickup to speed switch. Then wire from speed switch to the 2301A Governor. The speed switch may be installed physically near the 2301A if desired.

NOTED D: Electronic dual speed switch and electronic time delay relay can be wired to battery power continuously since the system will draw less than 40 MA current when the engine is not running.

NOTE E: If required, customer is to supply (RNS) Remote Normal Shutdown Switch. Requires a single pole N/O switch with a minimum contact rating of 5 amps inductive at the charging system voltage. Can be a latching switch if customer prefers. Shuts off engine fuel when activated.

NOTE F: If required, customer is to supply (RESS) Remote Emergency Shutdown Switch. Requires a single Pole N/O switch with a minimum contact rating of 5 amps inductive at the charging system voltage. Can be latching switch if customer prefers. Shuts off engine air and fuel when activated. This shutoff mode must not be used for normal engine shutdown.

Water Temperature And Oil Pressure Shutoff System

With Time Delay Relay

Wiring Diagram (Fuel Shutoff Solenoid Energized to Shutoff)
(1) Time delay relay. (2) Oil pressure switch. (3) Water temperature switch. (4) Switch (N/O). (5) Circuit breaker. (6) Shutdown relay. (7) Battery. (8) Diode assembly. (9) Fuel shutoff solenoid. (10) Starting motor.

When the engine starts, engine oil pressure will close the N/O switch and open the N/C switch in oil pressure switch (2). This completes the circuit to time delay relay (1). N/O switch (4) in the time delay relay now closes and completes the circuit between shutdown relay (6) and terminal TD-7 of the time delay relay.

If the engine coolant temperature goes above the setting of water temperature switch (3), the N/O contacts will close. This lets current flow through water temperature switch (3) and through switch (4) to activate shutdown relay (6) which in turn activates fuel shutoff solenoid (9). When the engine stops, engine oil pressure will become less than the setting of the oil pressure switch. The N/O switch will open and stop the flow of current to the time delay relay timer. After 70 seconds, switch (4) will open to stop current flow through shutdown relay (6). Now, fuel shutoff solenoid (9) will no longer be activated.

If engine oil pressure gets less than the setting of the oil pressure switch, the N/C switch will close. This will let current flow through switch (4) to activate shutdown relay (6) which in turn activates fuel shutoff solenoid (9). The N/O switch will open and start the time delay relay timer. After 70 seconds, switch (4) will open to stop current flow through shutdown relay (6). Now, fuel shutoff solenoid (9) will no longer be activated.

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to shutdown before the engine is started again.

Water Temperature, Oil Pressure And Electronic Overspeed Shutoff System

With Time Delay Relay

Wiring Diagram (Fuel Shutoff Solenoid Energized To Shutoff)
(1) Magnetic pickup. (2) Dual speed switch. (3) Overspeed switch. (4) Crank terminate switch. (5) Water temperature switch. (6) Oil pressure switch. (7) Time delay relay. (8) Switch (N/O). (9) Shutdown relay. (10) Battery. (11) Diode assembly. (12) Fuel shutoff solenoid. (13) Starting motor.

The engine speed is felt by magnetic pickup (1). As the teeth of the flywheel go through the magnetic lines of force around the pickup, an AC voltage is made. Dual speed switch (2) measures engine speed from the frequency of the voltage.

Time delay relay (7) controls the operation of shutdown relay (9), which in turn, controls the operation of fuel shutoff solenoid (12). Time delay relay (7) will keep the fuel shutoff solenoid energized for 70 seconds after a fault condition. This prevents the engine from being started again before the flywheel has stopped rotation.

When the engine starts and gets to a speed just above cranking speed, the normally open contacts of crank terminate switch (4) [which is part of dual speed switch (2)] will close. This will complete the circuit to time delay relay (7) through terminal TD-2. In approximately 9 seconds N/O switch (8) in time delay relay (7) will close and complete the circuit between shutdown relay (9) and terminal TD-7 of the time delay relay. If the engine oil pressure has not activated oil pressure switch (6) by 9 seconds, current will flow through the N/C switch in the oil pressure switch and through the now closed N/O switch (8) to activate shutdown relay (9) which in turn activates fuel shutoff solenoid (12). If engine oil pressure activates oil pressure switch (6), the N/O switch will close and the N/C switch will open. This will let current flow to terminal TD-1 of the time delay relay and immediately close N/O switch (8). At the same time the N/C switch in the oil pressure switch will open and prevent current flow to switch (8).

If the engine speed increases above the overspeed setting (118 percent of rated speed) of the dual speed switch, the overspeed switch (part of the dual speed switch) will close across terminals DSS-7 and DSS-8. This completes the circuit to shutdown relay (6) through the now closed switch (8) at terminal TD-7. Shutdown relay (9) is activated and in turn activates fuel shutoff solenoid (12) to cause the engine to shutdown.

When the engine speed gets less than the cranking speed setting, switch (4) opens. This stops the flow of current to terminal TD-2 of the time delay relay. When the engine stops, engine oil pressure will become less than the setting of the oil pressure switch. The N/O switch will open and stop the flow of current to terminal TD-1 of the time delay relay. This will start the time delay relay timer. After 70 seconds, switch (8) will open and stop current flow to shutdown relay (9) and fuel shutoff solenoid (12) will no loner be activated.

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to overspeed before the engine is started again.

After an overspeed shutdown, a button on the dual speed switch must be pushed to open the overspeed switch before the engine will run.

When the engine has been started and is running, the time delay relay will close switch (8). If the engine coolant temperature goes above the setting of water temperature switch (5), the N/O contacts will close. This lets current flow through the water temperature switch and through switch (8) to activate shutdown relay (9) and in turn activates fuel shutoff solenoid (12).

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to get too hot before the engine is started again.

When the engine has been started and is running, the time delay relay will close switch (8). If the engine oil pressure gets less than the setting of oil pressure switch (6), the N/C switch will close. This will let current flow through switch (8) to activate shutdown relay (9) and in turn activates fuel shutoff solenoid (12). The N/O switch will also open and stop current flow to terminal TD-1 of the time delay relay. When the engine speed gets less than the cranking speed setting, switch (4) opens. This stops the flow of current to terminal TD-2 of the time delay relay and starts the time delay relay timer. After 70 seconds, switch (8) will open and stop current flow to shutdown relay (9) and fuel shutoff solenoid (12) will no longer be activated.

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NOTICE

To help prevent damage to the engine, find and correct the cause for low engine oil pressure before the engine is started again.

Water Temperature, Oil Pressure And Electronic Overspeed With Air Shutoff

With Time Delay Relay

Wiring Diagram (Fuel Shutoff Solenoid Energized to Shutoff)
(1) Magnetic pickup. (2) Dual speed switch. (3) Overspeed switch. (4) Crank terminate switch. (5) Water temperature switch. (6) Oil pressure switch. (7) Time delay relay. (8) Switch (N/O). (9) Fuel shutdown relay. (10) Diode. (11) Air shutdown relay. (12) Fuel shutoff solenoid. (13) Air shutoff solenoid. (14) Starting motor. (15) Battery.

This system gives high water temperature, low oil pressure and overspeed protection. The air inlet shutoff system is used with fuel shutoff system to give overspeed protection to the engine and is activated only by an overspeed condition. The air inlet shutoff system consists of diode (10), shutdown relay (11), air shutoff solenoid (13) and a shutoff valve. The location of the shutoff valve and shutoff solenoid is in the air inlet pipe to the engine.

When an engine has an overspeed condition the air shutoff shutdown relay (11) is activated by the same signal from time delay relay (7) that activates fuel shutdown relay (9).

NOTE: See Water Temperature, Oil Pressure And Electronic Overspeed Shutoff System for more details of the systems operation.

After an overspeed condition, a reset button on the dual speed switch must be pushed to open the overspeed switch and the air inlet shutoff valves must be manually reset before the engine will run.

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to shutdown, before the engine is started again.

Diode (10) keeps the air shutoff solenoid circuit separate from the fuel shutoff circuit. This lets a manual shutdown switch be connected to fuel shutdown relay (9) and does not activate air shutdown relay (11) when the switch is closed to manually shutdown the engine.

Electronic Overspeed Shutoff System

With Time Delay Relay

Wiring Diagram (Fuel Shutoff Solenoid Energized To Shutoff)
(1) Magnetic pickup. (2) Crank terminate switch. (3) Dual speed switch. (4) Time delay relay. (5) Switch (N/O). (6) Shutdown relay. (7) Battery. (8) Diode assembly. (9) Fuel shutoff solenoid. (10) Starting motor.

The engine speed is felt by magnetic pickup (1). As the teeth of the flywheel go through the magnetic lines of force around the pickup, an AC voltage is made. Dual speed switch (3) measures engine speed from the frequency of this AC voltage.

Time delay relay (4) controls the operation of shutdown relay (6), which in turn, controls the operation of fuel shutoff solenoid (9). Time delay relay (4) will keep the fuel shutoff solenoid energized for 70 seconds after a fault condition. This prevents the engine from being started again before the flywheel has stopped rotation.

When the engine starts and gets to a speed just above cranking speed, the normally open contacts of crank terminate switch (2) [which is part of dual speed switch (3)] will close. This will complete the circuit to time delay relay (4) through terminal TD-1. Normally open switch (5) in time delay relay (4) now closes and completes the circuit between shutdown relay (6) and terminal TD-7.

If the engine speed increases above the overspeed setting (118 percent of rated speed) of the dual speed switch, the overspeed switch (part of the dual speed switch) will close across terminals DSS-7 and DSS-8. This completes the circuit to shutdown relay (6) through the now closed switch (5) at terminal TD-7. Shutdown relay (6) is activated and in turn activates fuel shutoff solenoid (9) to cause the engine to shutdown.

When the engine stops, crank terminate switch (2) will open the circuit across terminals DSS-10 and DSS-11. This stops current flow to time delay relay (4). Now, the time delay relay timer is started and 70 seconds later, switch (5) will open the circuit at terminal TD-7. Current flow is then stopped through shutdown relay (6) and fuel shutoff solenoid (9) will no longer be activated.

A reset button on the dual speed switch must be pushed to open the overspeed switch before the engine will run.

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to overspeed, before the engine is started again.

Electronic Overspeed With Air Shutoff

With Time Delay Relay

Wiring Diagram (Fuel Shutoff Solenoid Energized to Shutoff)
(1) Magnetic pickup. (2) Crank terminate switch. (3) Dual speed switch. (4) Time delay relay. (5) Switch (N/O). (6) Fuel shutdown relay. (7) Diode. (8) Air shutdown relay. (9) Fuel shutoff solenoid. (10) Air shutoff solenoid. (11) Starting motor. (12) Battery.

The air inlet shutoff system is used with the fuel shutoff system to give overspeed protection to the engine. The air inlet shutoff system consists of diode (7), shutdown relay (8), solenoid (10) and a shutoff valve. The location of the shutoff valve and shutoff solenoid is in the air inlet pipe to the engine.

When an engine has an overspeed condition, the air shutoff shutdown relay (8) is activated by the same signal from time delay relay (4) that activates fuel shutdown relay (6). See Electronic Overspeed Shutoff System for details of the system operation.

After an overspeed condition, a reset button on the dual speed switch must be pushed to open the overspeed switch and the air inlet shutoff valves must be manually reset before the engine will run.

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to overspeed, before the engine is started again.

Diode (7) keeps the air shutoff solenoid circuit separate from the fuel shutoff solenoid circuit. This lets a manual switch be connected to fuel shutdown relay (6) and does not activate air shutdown relay (8) when the switch is closed to manually shutdown the engine.

Alarm Contactor System

Wiring Diagram
(1) Oil pressure switch. (2) Water temperature contactor. (3) Source voltage. (4) Toggle switch (optional). (5) Alarm. (6) Signal lights.

If the oil pressure is too low or the water temperature is too high this system will activate alarm (5) and signal lights (6).

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NOTICE

When the alarm and signal lights activate, stop the engine immediately. This will help prevent damage to the engine from heat or not enough lubrication. Find and correct the problem that caused the alarm and signal lights to activate.

Before the engine is started it will be necessary to override oil pressure switch (1) or the alarm will activate. This is done by either a manual override button on the (earlier) oil pressure switch or toggle switch (4). Oil pressure will return the manual override button to the run position. The toggle switch must be manually closed when the engine has oil pressure.

Wiring Diagram
(1) Oil pressure switch. (2) Water temperature contactor. (3) Source voltage. (4) Toggle switch (optional). (6) Signal lights (three). (7) Air temperature contactor.

If the oil pressure is too low or the water temperature is too high this system will activate signal lights (6).

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NOTICE

When the signal lights activate, stop the engine immediately. This will prevent damage to the engine from heat or not enough lubrication. Find and correct the problem that caused the signal lights to activate.

Before the engine is started it will be necessary to override oil pressure switch (1) or the signal lights will activate. This is done by either a manual override button on the (earlier) oil pressure switch or toggle switch (4). Oil pressure will return the manual override button to the run position. The toggle switch must be manually closed when the engine has oil pressure.

Wiring Diagram
(1) Oil pressure switch. (2) Water temperature contactor. (3) Source voltage. (4) Toggle switch (optional). (5) Alarm. (7) Air temperature contactor.

If the oil pressure is too low or the water temperature is too high this system will activate alarm (5).

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NOTICE

When the alarm activates, stop the engine immediately. This will help prevent damage to the engine from heat or not enough lubrication. Find and correct the problem that caused the alarm to activate.

Water Temperature And Oil Pressure Shutoff System

With Oil Pressure Delay Or Fuel Pressure Switch

Wiring Diagram
(1) Oil pressure switch. (2) Water temperature contactor. (3) Oil pressure (time delay) or fuel switch. (4) Rack solenoid. (5) Diode assembly. (6) Starter. (7) Battery.

If the oil pressure is too low or the coolant temperature is too high this system will activate rack solenoid (4). The solenoid is connected to the fuel rack by linkage. When it is activated it will move to stop the flow of fuel to the engine. The engine will stop.

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to shutdown before the engine is started again.

Before the engine can be started it will be necessary to push the manual override button on (earlier) oil pressure switch (1). Oil pressure will return the manual override button to the run position.

Diode assembly (5) is used to stop arcing, for protection of the system.

Oil pressure delay or fuel pressure switch (3) is used to prevent discharge of battery (7) through the solenoid when the engine is stopped.

Electronic Overspeed Shutoff System

With Oil Pressure Delay Or Fuel Pressure Switch

Wiring Diagram
(1) Rack Solenoid. (2) Oil pressure (time delay) or fuel pressure switch. (3) Dual speed switch. (4) Magnetic pickup. (5) Diode assembly. (6) Starter. (7) Battery.

The engine speed is felt by magnetic pickup (4). As the teeth of the flywheel go through the magnetic lines of force around the pickup, an AC voltage is made. Dual speed switch (3) measures engine speed from the frequency of this AC voltage.

Rack solenoid (1) is connected to the fuel rack by linkage. When it is activated, it will move to stop the flow of fuel to the engine.

If the engine speed increases above the overspeed setting (118 percent of rated speed) of the dual speed switch, the overspeed switch [which is part of dual speed switch (3)] will close across terminals DSS-7 and DSS-8. This completes the circuit to rack solenoid (1) through the now closed oil pressure (time delay) or fuel pressure switch (2) and activates the solenoid to shutdown the engine.

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to overspeed, before the engine is started again.

After an overspeed shutdown, a button on the dual speed switch must be pushed to open the overspeed switch before the engine will run.

Diode assembly (5) is used to stop arcing, for protection of the system.

An oil pressure (time delay) or fuel pressure switch (2) is used to prevent discharge of battery (7) through the solenoid when the engine is stopped. The dual speed switch can be connected to the battery constantly because it uses less than 20 MA of current when the engine is stopped.

Electronic Overspeed With Air Shutoff

With Oil Pressure Delay Or Fuel Pressure Switch

Wiring Diagram
(1) Rack solenoid. (2) Oil pressure (time delay) or fuel pressure switch. (3) Dual speed switch. (4) Magnetic pickup. (5) Diode assembly. (6) Diode. (7) Air shutoff solenoids. (8) Starting motor. (9) Battery.

This system gives overspeed protection. Air shutoff solenoids (7) control a valve assembly in the air inlet pipe. When the solenoids are activated, the valve closes to shutoff air to the engine. When the engine has an overspeed condition, the air shutoff solenoids are activated by the same signal from the overspeed switch [part of dual speed switch (3)] that activates rack solenoid (1). See Electronic Overspeed Shutoff System for more detail of the system operation.

Diode assemblies (5) are used to stop arcing, for protection of the system.

Diode (6) keeps the air shutoff solenoid circuit separate from the rack solenoid circuit. For example, if a manual switch was connected to the rack solenoid, the air shutoff solenoids would not activate when the switch was closed.

After an overspeed condition, a reset button on the dual speed switch must be pushed to open the overspeed switch and the air inlet shutoff valves must be manually reset before the engine will run.

Water Temperature, Oil Pressure and Electronic Overspeed Shutoff System

With Oil Pressure Delay Or Fuel Pressure Switch

Wiring Diagram
(1) Oil pressure switch. (2) Oil pressure (time delay) or fuel pressure switch. (3) Water temperature contactor. (4) Dual speed switch. (5) Magnetic pickup. (6) Rack solenoid. (7) Diode assembly. (8) Starting motor. (9) Battery.

This system gives high water temperature, low oil pressure and overspeed protection to the engine.

Rack solenoid (6) is connected to the fuel rack by linkage. When it is activated it will move to stop the flow of fuel to the engine. The rack solenoid can be activated by oil pressure switch (1), water temperature contactor (3) or the overspeed switch that is part of dual speed switch (4).

If the oil pressure is too low or the coolant temperature is too high, oil pressure switch (1) or water temperature contactor (3) will close to complete the circuit and activate rack solenoid (6).

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to shutdown before the engine is started again.

The engine speed is felt by magnetic pickup (5). As the teeth of the flywheel go through the magnetic lines of force around the pickup, an AC voltage is made. Dual speed switch (4) measures engine speed from the frequency of this AC voltage.

If the engine speed increases above the overspeed setting (118 percent of rated speed) of the dual speed switch, the overspeed switch [which is part of dual speed switch (4)] will close across terminals DSS-7 and DSS-8. This completes the circuit rack solenoid (6) through oil pressure (time delay) or fuel pressure switch (2) and water temperature contactor (3) to activate the solenoid and shutdown the engine.

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to overspeed, before the engine is started again.

After an overspeed shutdown, a button on the dual speed switch must be pushed to open the overspeed switch before the engine will run.

Diode assembly (7) is used to stop arcing, for protection of the system.

An oil pressure (time delay) or fuel pressure switch (2) is used to prevent discharge of battery (9) through the solenoid when the engine is stopped. The dual speed switch can be connected to the battery constantly because it uses less than 20 MA current when the engine is stopped.

Water Temperature, Oil Pressure And Electronic Overspeed With Air Shutoff

With Oil Pressure Delay Or Fuel Pressure Switch

This system gives high water temperature, low oil pressure and overspeed protection. The air inlet shutoff system is used with the fuel shutoff system to give overspeed protection to the engine and is activated only by an overspeed condition. The air inlet shutoff system consist of diode (8), air shutoff solenoid (9) and a shutoff valve. The location of the shutoff valve and shutoff solenoid is in the air inlet pipe to the engine. Engines with two turbochargers have two shutoff valves and solenoids.

When an engine has an overspeed condition air shutoff solenoid (9) is activated by the same signal from the overspeed switch [which is part of dual speed switch (4)] that activates rack solenoid (6).

NOTE: See Water Temperature, Oil Pressure And Electronic Overspeed Shutoff System for more details of the systems operation.

After an overspeed condition, a reset button on the dual speed switch must be pushed to open the overspeed switch and the air inlet shutoff valves must be manually reset before the engine will run.

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NOTICE

To help prevent damage to the engine, find and correct the problem that caused the engine to shutdown, before the engine is started again.

Diode (8) keeps the air shutoff solenoid circuit separate from the fuel shutoff circuit. This lets a manual shutdown switch be connected to rack solenoid (6) and does not activate air shutoff solenoid (9) when the switch is closed to manually shutdown the engine.

NOTE: On systems that use an earlier type oil pressure switch, it will be necessary to push the manual override button before the engine can be started. Oil pressure will return the manual override button to the run position.

Mechanical Shutoff And Alarm Systems

Mechanical Oil Pressure And Water Temperature Shutoff

Mechanical Oil Pressure And Water Temperature Shutoff (4W1979 Shown)
(1) Outlet line. (2) Inlet line. (3) Drain line. (4) Shut down cylinder knob. (5) Water temperature control valve. (6) Shut down cylinder inlet port. (7) Oil pressure shut down cylinder. (8) Oil pressure control valve.

System Schematic

Oil pressure shut down cylinder (7) is fastened to the governor. Before the engine is started the shut down cylinder knob (4) is used to pull a piston away from the fuel rack and compresses a pressure spring. With the shut down cylinder knob (4) held in this position the engine can be started.

When the engine starts, oil pressure will build in the oil pressure control valve (8). When oil pressure is high enough, pressure oil will flow from the oil pressure control valve (8) through the shut down cylinder oil inlet port (6) into the space between the piston and the housing. As long as the engine has enough oil pressure the fuel rack will be controlled by the governor.

If the engine oil pressure gets too low the oil pressure control valve (8) will divert pressure oil back to the crankcase. This will create a loss of oil pressure in the oil pressure shut down cylinder. The force of the compression in the spring will overcome the oil pressure and move the piston against the fuel rack. This will move the rack to stop the flow of fuel to the engine. The engine will stop.

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NOTICE

Find and correct the problem that caused the engine to stop. This will help prevent damage to the engine from not enough lubrication.

Temperature Shutoff Control Valve
(9) Inlet Port. (10) Outlet Port. (11) Thermostat assembly. (12) Drain port.

Water temperature shutoff (5) is a control valve for the oil pressure shutoff. When the water temperature becomes too high the thermostat assembly (11) causes an internal valve to move. Pressure oil at inlet port (9) will then be diverted inside the valve from the output port (10) to the drain port (12)). The diverted pressure oil will flow out the drain port (12) into the engine crankcase. This will cause the oil pressure to decrease. The oil pressure control valve (8) will sense this and divert oil from the shut down cylinder (7) to the crankcase causing a loss of pressure oil in the shut down cylinder (7). This will move the rack to stop the flow of fuel to the engine. The engine will stop.

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NOTICE

Find and correct the problem that caused the engine to stop. This will help prevent damage to the engine from too much heat.

Shutoff And Alarm System Components

Oil Pressure Switch

Micro Switch Type

Oil Pressure Switch (Micro Switch Type)
(1) Locknut. (2) Adjustment screw. (3) Spring. (4) Arm. (5) Spring. (6) Bellows. (7) Latch plate. (8) Button (for micro switch). (9) Arm. (10) Projection (of arm).

The oil pressure switch is used to give protection to the engine from damage because of low pressure. When oil pressure lowers to the pressure specifications of the switch, the switch closes and activates the rack shutoff solenoid.

On automatic start/stop installations, this switch closes to remove the starting system from the circuit when the engine is running with normal oil pressure.

This switch for oil pressure can be connected in a warning system for indication of low oil pressure with a light or horn.

As pressure of the oil in bellows (6) becomes higher, arm (4) is moved against the force of spring (3). When projection (10) of arm (4) makes contact with arm (9), pressure in the bellows moves both arms. This also moves button (8) of the micro switch to activate the micro switch.

Some of these switches have a "Set For Start" button. When the button is pushed in, the micro switch is in the START position. This is done because latch plate (7) holds arm (9) against button (8) of the micro switch and the switch operates as if the oil pressure was normal. When the engine is started, pressure oil flows into bellows (6). The bellows move arm (4) into contact with latch plate (7). The latch plate releases the "Set For Start" button and spring (5) moves it to the RUN position. This puts the switch in a ready to operate condition.

Pressure Switch

Pressure switches are used for several purposes and are available with different specifications. They are used in the oil system and in the fuel system. One use of the switch is to open the circuit between the battery and the rack shutoff solenoid after the oil pressure is below the pressure specifications of the switch. It also closes when the engine starts.

Another use of the switch is to close and activate the battery charging circuit when the pressure is above the pressure specification of the switch. It also disconnects the circuit when the engine is stopped.

Switches of this type have three terminal connections. They are used to do two operations with one switch. They open one circuit and close another with the single switch.

Shutoff Solenoid

Rack Shutoff Solenoid (Typical Illustration)

A shutoff solenoid changes electrical input into mechanical output. It is used to move the fuel injection pump rack to the off position. It can also be used to move a valve assembly in the air inlet pipe to a closed position. This stops the engine.

The shutoff solenoid can be activated by any one of the many sources. The most usual are: water temperature contactor, oil pressure switch, overspeed switch and remote manual control switch.

Water Temperature Contactor Switch

The contactor switch for water temperature is installed in the water manifold. No adjustment to the temperature range of the contactor can be made. The element feels the temperature of the coolant and then operates the micro switch in the contact when the coolant temperature is too high, the element must be in contact with the coolant to operate correctly. If the cause for the engine being too hot is because of low coolant level or no coolant, the contactor switch will not operate.

The contactor switch is connected to the rack shutoff solenoid to stop the engine. The switch can also be connected to an alarm system. When the temperature of the coolant lowers to the operating range, the contactor switch opens automatically.

Circuit Breaker

Circuit Breaker Schematic
(1) Disc (in open position). (2) Contacts. (3) Disc. (4) Circuit terminals.

The circuit breaker gives protection to an electrical circuit. Circuit breakers are rated as to how much current they will permit to flow. If the current in a circuit gets too high it will cause heat in disc (3). Heat will cause distortion of the disc and contacts (2) will open. No current will flow in the circuit.

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NOTICE

Find and correct the problem that caused the circuit breaker to open. This will help prevent damage to the circuit components from too much current.

An open circuit breaker will close (reset) automatically when it becomes cooler.

Electronic Speed Switch

Electronic Speed Switch
(1) Reset button. (2) Lamp.

The electronic speed switch (dual speed switch) activates the shutoff solenoid when the engine speed gets approximately 18 percent higher than the rated full load speed of the engine. It also stops current flow to the starting motor after the engine starts.

The electronic speed switch makes a comparison between the output frequency of the magnetic pickup and the setting of the electronic speed switch. When they are equal, the normally open contacts in the electronic speed switch close. Lamp (2) will go on. The switch also has a failsafe circuit that will cause the engine to shutdown if there is an open in the magnetic pickup circuit.

When the engine is stopped, it will be necessary to push reset button (1), before the engine can be started.

Starting System Components

Solenoid

Typical Solenoid Schematic

A solenoid is a magnetic switch that does two basic operations.

a. Closes the high current starting motor circuit with a low current start switch circuit.

b. Engages the starting motor pinion with the ring gear.

The solenoid switch is made of an electromagnet (one to two sets of windings) around a hollow cylinder. There is a plunger (core) with a spring load inside the cylinder that can move forward and backward. When the start switch is closed and electricity is sent through the windings, a magnetic field is made that pulls the plunger forward in the cylinder. This moves the shift lever (connected to the rear of the plunger) to engage the pinion drive gear with the ring gear. The front end of the plunger then makes contact across the battery and motor terminals of the solenoid, and the starting motor begins to turn the flywheel of the engine.

When the start switch is opened, current no longer flows through the windings. The spring now pushes the plunger back to the original position, and at the same time, moves the pinion gear away from the flywheel.

When two sets of windings in the solenoid are used, they are called the hold-in winding and the pull-in winding. Both have the same number of turns around the cylinder, but the pull-in winding uses a larger diameter wire to produce a greater magnetic field. When the start switch is closed, part of the current flows from the battery through the hold-in winding, and the rest flows through the pull-in windings to the motor terminal, then through the motor to ground. When the solenoid is fully activated (connection across battery and motor terminal is complete), current is shut off through the pull-in windings. Now only the smaller hold-in windings are in operation for the extended period of time it takes to start the engine. The solenoid will now take less current from the battery, and heat made by the solenoid will be kept at an acceptable level.

Electric Starting System

The starting motor is used to turn the engine flywheel fast enough to get the engine to start running.

The starting motor has a solenoid. When the start switch is activated, the solenoid will move the starter pinion to engage it with the ring gear on the flywheel of the engine. The starter pinion will engage with the ring gear before the electric contacts in the solenoid close the circuit between the battery and the starting motor. When the circuit between the battery and the starting motor is complete, the pinion will turn the engine flywheel. A clutch gives protection for the starting motor so that the engine can not turn the starting motor too fast. When the start switch is released, the starter pinion will move away from the ring gear.

Starting Motor Cross Section
(1) Field. (2) Solenoid. (3) Clutch. (4) Pinion. (5) Commutator. (6) Brush Assembly. (7) Armature.

Air Starting System

The air starting motor is used to turn the engine flywheel fast enough to get the engine running.

Typical Air Starting System
(1) Air start control valve. (2) Air starting motor. (3) Relay valve. (4) Oiler.

The air starting motor (2) can be mounted on either side of the engine. Air is normally contained in a storage tank and the volume of the tank will determine the length of time the engine flywheel can be turned. The storage tank must hold this volume of air at 1720 kPa (250 psi) when filled.

For engines which do not have heavy loads when starting, the regulator setting is approximately 690 kPa (100 psi). This setting gives a good relationship between cranking speeds fast enough for easy starting and the length of time the air starting motor can turn the engine flywheel before the air supply is gone.

If the engine has a heavy load which can not be disconnected during starting, the setting of the air pressure regulating valve needs to be higher in order to get high enough speed for easy starting.

The air consumption is directly related to speed; the air pressure is related to the effort necessary to turn the engine flywheel. The setting of the air pressure regulator can be up to 1030 kPa (150 psi) if necessary to get the correct cranking speed for a heavily loaded engine. With the correct setting, the air starting motor can turn the heavily loaded engine as fast and as long as it can turn a lightly loaded engine.

Other air supplies can be used if they have the correct pressure and volume. For good life of the air starting motor, the supply should be free of dirt and water. A lubricator with SAE 10 non detergent oil [for temperatures above 0°C (32°F)], or diesel fuel [for temperatures below 0°C (32°F)] should be used with the starting system. The maximum pressure for use in the air starting motor is 1030 kPa (150 psi).

Air Starting Motor
(5) Air inlet. (6) Vanes. (7) Rotor. (8) Pinion. (9) Gears. (10) Piston. (11) Piston spring.

The air from the supply goes to relay valve (3). The starter control valve (1) is connected to the line before the relay valve. The flow of air is stopped by the relay valve until starter control valve (1) is activated. The air from starter control valve goes to piston (10) behind pinion (8) for the starter. The air pressure on piston (10) puts spring (11) in compression and puts pinion (8) in engagement with the flywheel gear. When the pinion is in engagement, air can go out through another line to relay valve. The air activates relay valve which opens the supply line to the air starting motor.

The flow of air goes through the oiler (lubricator) (4) where it picks up lubrication for the air starting motor.

The air with lubrication goes into the air motor through air inlet (5). The pressure of the air pushes against vanes (6) in rotor (7), and then exhausts through the outlet. This turns the rotor which is connected by gears (9) and a drive shaft to starter pinion (8) which turns the engine flywheel.

When the engine starts running, the flywheel will start to turn faster than the starter pinion (8). The pinion (8) retracts under this condition. This prevents damage to the motor, pinion (8) or flywheel gear.

When start control valve (1) is released, the air pressure and flow to piston (10) behind starter pinion (8) is stopped, piston spring (11) retracts pinion (8). Relay valve (3) stops the flow of air to the air starting motor.

Power Take-Off Clutch

Power Take-Off Clutch (Typical Illustration)
(1) Ring. (2) Driven discs. (3) Link assemblies. (4) Lever. (5) Key. (6) Collar assembly. (7) Nut. (8) Yoke assembly. (9) Hub. (10) Plates. (11) Output shaft.

Power take-off clutches (PTOs) are used to send power from the engine to accessory components. For example, a PTO can be used to drive an air compressor or a water pump.

The PTO is driven by a ring (1) that has spline teeth around the inside diameter. The ring can be connected to the front or rear of the engine crankshaft by an adapter.

NOTE: On some PTOs located at the rear of the engine, ring (1) is a part of the flywheel.

The spline teeth on the ring engage with the spline teeth on the outside diameter of driven discs (2). When lever (4) is moved to the ENGAGED position, yoke assembly (8) moves collar assembly (6) in the direction of the engine. The collar assembly is connected to four link assemblies (3). The action of the link assemblies will hold the faces of driven discs (2), drive plates (10) and hub (9) tight together. Friction between these faces permits the flow of torque from ring (1), through driven discs (2), to plates (10) and hub (9), Spline teeth on the inside diameter of the plates drive the hub. The hub is held in position on the output shaft (11) by a taper, nut (7) and key (5).

NOTE: A PTO can have from one to three driven discs (2) with a respective number of plates.

When lever (4) is moved the NOT ENGAGED position, yoke assembly (8) moves collar assembly (6) to the left. The movement of the collar assembly will release link assemblies (3). With the link assemblies released there will not be enough friction between the faces of the clutch assembly to permit a flow of torque.