Systems Operation

Usage:

Introduction

NOTE: For Specifications with illustrations, make reference to Specifications for 3500 Spark Ignited Engine Attachments, Form No. SENR3105. If the Specifications in Form SENR3105 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.

3161 Governor

Refer to Caterpillar 3161 Governor Service Manual, Form No. SENR3028 for additional information.

3161 Generator Set Governor
(1) Manual speed setting control. (2) Speed adjusting motor head. (3) External droop adjustment.

The 3161 Governor is a mechanical-hydraulic governor that senses (feels) engine speed and is connected to the carburetor by mechanical linkage. The governor controls the rate of fuel and air that is mixed in the carburetor. The fuel air mixture enters the inlet manifold and then goes into the cylinders for combustion as needed for engine loads.

The speed adjusting motor is located on the governor cover and runs on 24 volt DC power. When the motor is actuated, it rotates a speed adjusting screw to adjust the position of the governor speed adjusting lever.

Engine speed can be increased or decreased by the slotted speed setting adjustment located on the front of the governor. Turn the speed setting adjustment clockwise to increase the speed setting, and counterclockwise to decrease the speed setting. The high and low speed stops will limit the adjustments.

Droop and compensation can be adjusted on the governor as needed for stability of engines with different rates of engine speed changes.

The 3161 Governor has a maximum of 8 N·m (6 lb ft) of torque output over the full 42 degrees of terminal (output) shaft rotation in both the fuel ON and OFF directions. Because the governor terminal shafts are moved in both directions by hydraulic pressure, no return spring is used on the outside of the governor. A 1.4 N·m (1 lb ft) spring inside the governor moves the terminal shafts to the full shutoff position when the governor is not in operation.

The recommended travel (rotation) of the terminal shafts is approximately 30 degrees from low idle to full load. This gives extra travel at each end for the governor to make a complete shutdown and gives maximum fuel when needed.

The 3161 Governor is connected to the engine lubrication oil system. The oil supply (under pressure) is sent to the governor through an orifice and internal passages. The governor keeps the correct oil level and drains excess oil back into the engine, this gives a constant flow of oil through the governor.

After removal or overhaul, the governor must be filled with approximately 1.8 liters (2 U.S. qts) of clean engine oil before engine startup. The oil fill plug on the 3161 Governor is located on the top cover.

Schematic of the 3161 Governor (Increased Fuel Position)

Operation Of The 3161 Governor

Refer to Caterpillar 3161 Governor Service Manual, Form No. SENR3028 for additional information.

Make reference to the 3161 Governor Schematic for use with the system operation that follows. The schematic shows the governor pilot valve in the increased fuel position.

The 3161 Governor uses engine lubrication oil for its hydraulic system. The oil supply (under pressure) is sent to the governor oil reservoir through an orifice which can be removed from the governor housing for cleaning. The oil goes through internal passages to the suction side and then to the pressure side of the gerotor pump as the drive shaft is turned by the engine. An accumulator spring and piston keeps the pump pressure at approximately 690 kPa (100 psi). The accumulator piston moves up in its cylinder until the pump pressure is 690 kPa (100 psi). At this time, ports in the piston are opened to control the pump pressure.

The pump pressure, as set by the accumulator, controls the work output of the governor.

Increase In Speed Setting

When the speed setting shaft is turned clockwise, the speed setting of the governor is increased. The high idle screw limits the high speed setting of the governor. As the speed setting shaft turns, the speed setting lever pushes down on the floating lever which is fastened to the speeder plug. The downward pressure on the speeder plug puts the speeder spring under compression. The speeder spring force then becomes greater than the centrifugal force of the ballhead flyweights, and the ballhead pilot valve plunger is moved down. This increases the governor speed setting.

As the pilot valve plunger is moved down, pressure oil moves under the power piston and pushes the piston up. This moves the terminal lever up and the output shafts are turned in the "increase" fuel direction to increase the engine speed.

Before the engine gets to the new set speed, the compensation system starts to move the pilot valve plunger back to its center position and put the governor under stable control as follows.

The oil above the power piston is connected to the upper side of the buffer piston and lower side of the pilot valve compensation land. As the power piston moves up the oil pressure moves the buffer piston down and increases the compression of the lower buffer piston spring. The force of the spring works against the buffer piston movement and this results in a small increase in oil pressure on the upper side of the buffer piston. This higher pressure is directed to the lower side of the pilot valve compensation land and makes a force to push the pilot valve plunger up toward its center position. This stops the flow of pressure oil to the lower side of the power piston and movement of the piston is stopped.

As the pilot valve plunger is returned to its center position and the power piston movement is stopped, there is oil leakage through the needle valve orifice. This lets the oil pressure above and below the pilot valve compensation land become equal and the pilot valve plunger movement is stopped and the engine speed is returned to a stable condition. As the pressure above and below the compensation land become equal, the buffer springs return the buffer piston to its center position.

NOTE: An increase or decrease in engine load will give the similar governor movement as an increase or decrease in governor speed setting.

Shutdown

The limit/shutdown pilot valve is located in the pump oil pressure supply line to the ballhead pilot valve. When the engine shutdown system is activated, the limit/shutdown rod pushes the limit/shutdown pilot valve plunger below the supply passage. This drains oil from the supply to the ballhead pilot valve plunger. Control oil from under the power piston now drains past the control land of the pilot valve plunger. The power piston then moves down and the output shaft is turned in the "decreased fuel" direction. As the engine speed decreases, the ballhead flyweights move in and this lowers the ballhead pilot valve. Oil from under the power piston is now drained to the governor sump at a faster rate. As the power piston continues to move down, the output shaft is turned to the shutdown position until the engine is stopped.

Lubrication System

Duplex Oil Filter System

Duplex Oil Filter (Control Valve Shown in Main Run Position)
(1) Main filter housing. (2) Bypass valve. (3) Auxiliary filter housing. (4) Handle. (5) Fill valve. (6) Linkage. (7) Control valve shafts.

The duplex oil filter system makes it possible to change the filter elements while the engine is running at any speed.

During normal operation, the control valve should be in the "MAIN RUN" position. The oil then will be cleaned by the main filter elements (8) in the main filter housing (1) and the filtered oil will move check valve (10) to the right to close off the oil passage in auxiliary housing (3) (position shown in Section A-A). In this position, the auxiliary filter element can be changed after the oil pressure is released and the auxiliary housing is drained.

When handle (4) is pulled out to the "Auxiliary Run" position, the oil will be cleaned by the auxiliary filter element. The filtered oil will now move check valve (10) to the left to close passage in main filter housing. In this position, the main filter elements (8) can be changed after the oil pressure is released and the main filter housing is drained.

Section A-A
(8) Main filter elements. (9) Control valve assembly. (10) Check valve. (11) Auxiliary filter element.

After the filter elements in either housing have been changed, the housing must be filled again to maintain constant oil pressure when oil is directed from one filter housing to the other.

To fill either filter housing with oil, move fill valve (5) to the open position for a minimum of 5 minutes. This will direct oil through a small line to fill the empty filter housing.

Oil Level Regulator

Oil Level Control Schematic
(1) Vent to front housing. (2) Regulator. (3) Vent. (4) Oil supply. (5) Engine oil pan. (6) Valve. (7) Float. (8) Pivot. (9) Valve seat.

The regulator is used for a visual check of the oil level in the engine oil pan. A plug from the bottom of the regulator can be removed and an external oil supply line connected to the regulator housing. A float located inside the regulator controls a valve which maintains the correct oil level in the oil pan.

Electrical System

Electrical Gauges And Sending Units

The electrical gauges and sending units operate in electrical balance. Because of this, the voltage and resistance ratings are important to get the correct indications on the gauges. The chart shows components that operate together.

Sending Unit For Water Temperature

Sending Unit for Water Temperature
(1) Connection. (2) Nut. (3) Bulb.

The sending unit for water temperature is an electrical resistance. It changes the value of its resistance according to the temperature which the bulb (3) feels.

The sending unit is in a series circuit with the electrical gauge. When the temperature is high, the resistance is high. This makes the gauge have a high reading.

The sending unit must be in contact with the coolant. If the coolant level is too low because of a sudden loss of coolant while the engine is running or because the level is too low before starting the engine, the sending unit will not work correctly.

Sending Unit for Oil Pressure

Sending Unit for Oil Pressure
(1) Connection. (2) Fitting.

The sending unit for oil pressure is an electrical resistance. It has a material which changes electrical resistance according to pressure which it feels.

The sending unit for oil pressure is in a series circuit with the electrical gauge. As the pressure on the sending unit changes, the reading on the gauge changes in the same way.

Electric Service Meter

The electric hour meter is self-powered. A magnetic pickup mounted on the flywheel housing provides voltage (starting at 200 engine rpm) to power the electric service meter which records clock hours with quartz accuracy. A separate magnetic pickup must be used for each service meter; it cannot be shared with the digital tachometer, electronic speed switch, or electronic governor magnetic pickup.

Magnetic Pickup

Schematic of Magnetic Pickup

The magnetic pickup is a single pole, permanent magnet generator made of wire coils around a permanent magnet pole piece. As the teeth of the flywheel ring gear go through the magnetic lines of force around the pickup, an AC voltage is made. The ratio between the frequency at this voltage and the speed of the engine is directly proportional.

Contactor Switch (Water Temperature)

Water Temperature Contactor Switch

A water temperature sending unit is located in the cooling system. The unit is nonadjustable. Thermal expansion of the element operates a micro-switch that signals the shutoff solenoid which causes engine shutdown. The water temperature element must be in contact with the coolant. If overheating occurs due to low coolant level or no coolant, the sending unit will not function.

The water temperature sending unit can also be wired into an alarm system or light to signal high water temperature. After an overheated engine is allowed to cool, the contactor automatically resets itself.

Altronic Overspeed Switch

Show/hide table

Improper installation or operation of the shutdown system may not protect the equipment as intended, and may pose the threat of personal injury to the operator.

The Overspeed Switch is an engine overspeed device for use with ignition systems with a primary voltage of 200 VDC or lower. If an overspeed occurs the output switch latches for 20 to 30 seconds and then automatically resets. Wait at least 30 seconds before attempting to restart the engine after an overspeed occurs.

The Overspeed Switch is a solid state unit which operates directly from capacitor discharge systems. The Overspeed Switch requires no outside power source. The overspeed switch consists of a digital counting circuit activating a solid state switch. The counter operates on a .25 to .38 second time base for a fast reaction to an overspeed condition. The ignition input voltage must be 100 volts peak or higher at the trip point for proper operation.

Altronic Annunciator

Altronic Annuciator

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Improper installation or operation of the shutdown system may not protect the equipment as intended, and may pose the threat of personal injury to the operator. The sensor leads from the system operate at a very low voltage and must not contact any external voltage source. Damage to the system will result from the connection between the sensor leads and the ignition system of any AC or DC power source.

The Altronic Annunciator is an electronic monitor and shutdown device. There are three push button switches on the front of the annunciator unit: STOP (red), RESET (green) and TEST (yellow). There is also a digital readout where codes are displayed about the status of the Altronic Overspeed Protection system. The Altronic Annunciator system consists of the annunciator and a cable assembly. The power requirement is extremely low, allowing operation from the capacitor-discharge ignition system.

Overspeed Contactor Switch

Overspeed Contactor
(1) Reset button.

The overspeed contactor is used in a self powered electrical shutoff system to supply the electrical power to operate the system. It also contains a micro switch that is activated by high engine speed. It protects the engine from damage due to overspeeding. The overspeed switch is mounted on the tachometer drive. If the engine overspeeds, the switch contacts close and activate the gas shutoff valve and connect the magneto to ground to shut down the engine. When the engine shuts down because of overspeeding, the overspeed contactor switch must be reset by pushing reset button (1).

Shutoff System

Wiring Diagram For Self Powered Shutoff System

Wiring Schematic (JIC Symbols) For Self Powered Shutoff System

See the Wiring Diagram For Self Powered Shutoff System for Notes and Abbreviations used on the above schematic.

Altronic Overspeed Protection

Wiring schematic for Altronic Overspeed Protection

Wiring Diagrams

Tachometer

Wiring Diagram for Tachometer Circuit
(1) Magnetic pickup. (2) Tachometer. (3) Second tachometer (if used). (4) Ground connection (ground to engine). (5) Wiring connections for second tachometer, if used (all wires must be 22 AWG shielded cable or larger).