Systems Operation

Usage:

Introduction

NOTE: For Specifications with illustrations, make reference to Specifications for 3500 Spark Ignited Engine Attachments, Form No. SENR4603. If the Specifications in Form SENR4603 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.

Engine Design

3508

Cylinder And Valve Location

Number And Arrangement Of Cylinders ... 60°V-8

Valves Per Cylinder ... 4

Bore ... 170 mm (6.7 in)

Stroke ... 190 mm (7.5 in)

Compression Ratio ... Refer to nameplate on engine

Type Of Combustion ... Spark Ignited

Crankshaft Rotation (as viewed from flywheel end) ... Counterclockwise

Magneto Rotation (as viewed from flywheel end) ... Clockwise

Firing Order ... 1-2-7-3-4-5-6-8

Valve Setting

Intake ... 0.51 mm (.020 in)

Exhaust ... 1.02 mm (.040 in)

NOTE: Front of engine is opposite flywheel end. Left and right side of engine are as seen from flywheel end. No. 1 cylinder is front cylinder on right side. No. 2 cylinder is front cylinder on left side.

3512

Cylinder And Valve Location

Number And Arrangement Of Cylinders ... 60°V-12

Valves Per Cylinder ... 4

Bore ... 170 mm (6.7 in)

Stroke ... 190 mm (7.5 in)

Compression Ratio ... Refer to nameplate on engine

Type Of Combustion ... Spark Ignited

Crankshaft Rotation (as viewed from flywheel end) ... Counterclockwise

Magneto Rotation (as viewed from flywheel end) ... Clockwise

Firing Order ... 1-12-9-4-5-8-11-2-3-10-7-6

Valve Setting

Intake ... 0.51 mm (.020 in)

Exhaust ... 1.02 mm (.040 in)

3516

Cylinder And Valve Location

Number And Arrangement Of Cylinders ... 60°V-16

Valves Per Cylinder ... 4

Bore ... 170 mm (6.7 in)

Stroke ... 190 mm (7.5 in)

Compression Ratio ... Refer to nameplate on engine

Type Of Combustion ... Spark Ignited

Crankshaft Rotation (as viewed from flywheel end) ... Counterclockwise

Magneto Rotation (as viewed from flywheel end) ... Clockwise

Firing Order ... 1-2-5-6-3-4-9-10-15-16-11-12-13-14-7-8

Valve Setting

Intake ... 0.51 mm (.020 in)

Exhaust ... 1.02 mm (.040 in)

Abbreviations And Symbols

SI Timing Control System (Detonation Sensitive Timing)

SI Timing Control System

Ignition System

SI Timing Control (Detonation Sensitive Control)

The SI Timing Control (Detonation Sensitive Control) ignition system has the following components: a magneto, ignition transformers for each cylinder, wiring harness, spark plugs, the timing control module, the Altronic interface box, and the control group (detonation sensitive timing).

The function of the SI Timing Control System (detonation sensitive timing) is:

1. To provide the best engine performance at all engine speeds by retarding timing from an initial timing value.

2. To protect the engine from damage due to detonation by retarding the timing. If detonation persists, the control shuts down the engine.

Component Location
(1) Magneto. (2) Ignition transformer. (3) Wiring harness. (4) Detonation sensor. (5) Altronic interface box.

Magneto (Altronic)

Solid State Magneto (Altronic)
(1) Electronic firing section. (2) Alternator section. (3). Altronic interface box input connector. (4) Altronic interface box. (5) Magneto output connector.

The Altronic magneto is made of a permanent magnet alternator section (2) and breakerless electronic firing section (1). There are no brushes or distributor contacts.

Cross Section Of Solid State Magneto (Altronic)
(3) Altronic interface box input connector. (5) Magneto output connector. (6) Alternator. (7) Vent. (8) Speed reduction gears. (9) Pick-up coil. (10) Drive tang. (11) Energy storage capacitor. (12) Rotating timer arm. (13) SCR Solid state switch.

The engine turns magneto drive tang (10). The drive tang turns alternator (6), speed reduction gears (8) and rotating timer arm (12). As the alternator is turned it provides power to charge energy storage capacitor (11). There are separate pick-up coils (9) and SCR (silicon controlled rectifier) solid state switches (13) for each engine cylinder. The timer arm passes over pick-up coils (9) in sequence. The pick-up coils send signals to the Altronic Interface Box which then turn on solid state switches (13) which release the energy stored in capacitor (11). This energy leaves the magneto through output connector (5). The energy travels through the wiring harness to the ignition coils where it is transformed to the high voltage needed to fire the spark plugs.

Altronic Interface Box (AIB)

The Altronic Interface Box (AIB) receives signals from the Timing Control Module, which define how much the engine timing should be retarded. The AIB thenn sends signals to the magneto, telling it when to fire the spark plugs. The AIB also sends signals back to the Timing Control Module which indicates when the spark plugs fire.

Wiring Diagrams

3508 Engines With Altronic Magneto
Firing Order 1-2-7-3-4-5-6-8 Pin Order A-I-H-F-E-D-C-B

3512 Engines With Altronic Magneto
Firing Order 1-12-9-4-5-8-11-2-3-10-7-6 Pin Order A-M-L-K-J-I-H-F-E-D-C-B

3516 Engines With Altronic Magneto
Firing Order 1-2-5-6-3-4-9-10-15-16-11-12-13-14-7-8 Pin Order A-T-S-R-P-N-M-L-K-J-H-F-E-D-C-B

Ignition Transformer

The ignition transformer causes an increase of the magneto voltage. This is needed to send a spark (impulse) across the electrodes of the spark plugs. For good operation, the connections (terminals) must be clean and tight. The negative transformer terminals for each transformer are connected together and to ground.

Control Group (Detonation Sensitive Timing)

The control group consists of a Speed Sensor (TCMPU), a Crank Angle Sensor (CAS), and two Control Groups (Detonation Sensor). A Control Group is located on a camshaft cover on each side of the engine, and detects detonation through the detonation sensor.

The sensors produce electronic signals which are sent to the Timing Control Module. The TCM measures engine speed, detonation, and timing and calculates how much if any the timing should be retarded. The TCM then sends signals to the AIB to control engine timing.

Detonation Sensor

The Detonation Sensors (RHDS and LHDS) each consist of an accelerometer connected to a buffer module. The accelerometer produces a voltage signal proportional to engine detonation. The buffer module amplifies this signal and sends it to the TCM.

Speed Sensor (TCMPU)

The Speed Sensor (TCMPU) produces a signal whenever a ring tooth passes it. This signal is sent to the TCM to indicate engine speed.

Crank Angle Sensor (CAS)

The Crank Angle Sensor (CAS) produces a signal once every revolution. This signal is sent to the TCM to indicate the crankshaft angle. The TCM determines engine timing by comparing when the number 1 cylinder spark plug fires in relation to the crank angle signal.

Timing Control Module (TCM)

Timing Control Module

The Timing Control Module (TCM) monitors the engine speed, crankshaft position and the engine for detonation through the two detonation sensors.

The Speed Sensor (TCMPU) is mounted in the top of the flywheel housing and detects the engine speed from the flywheel ring gear.

The Crank Angle Sensor (CAS) is mounted in the front of the flywheel housing and detects the crankshaft angle. The TCM determines engine timing by comparing when the number 1 cylinder spark plug fires in relation to the crank angle signal.

The Detonation Sensors (RHDS) (LHDS) are mounted on valve covers (one on each bank of cylinders). The detonation sensors monitor engine detonation. If detonation is detected the timing is retarded. If the engine stays in detonation after the timing has been retarded, the Timing Control Module will shut down the engine. The TCM also controls timing based upon engine speed.

The Altronic Interface Box (AIB) receives signals from the TCM, which define how much the engine timing should be retarded. The AIB then sends signals to the magneto, telling it when the fire the spark plugs. The AIB also sends signals back to the TCM which indicate when the spark plugs fire. The magneto will not fire if the Timing Control Module and the Altronic Interface Box are not hooked up and running properly.

Diagnostic lights are provided on the Timing Control Module. These lights should be used for troubleshooting and monitoring engine conditions. The lights should indicate what part of the system needs investigating and possible replacement.

The DDT (Digital Diagnostic Tool) service tool is provided to set up the SI Timing Control, monitor engine functions, and provide diagnostics. The service tool can monitor engine speed, timing and detonation levels. It is also used to time (calibrate) the magneto.

Timing is retarded 6° according to engine speed. The amount of timing retard for engine speeds is given in the Timing Maps below. Note there are three Timing Maps available, and are selectable using the 8C9904 Digital Diagnostic Tool (DDT) Group.

Timing is also retarded up to an additional 6° due to engine detonation. When severe or prolonged detonation occurs, the timing is retarded 6°. Engine detonation can be monitored using the 8C9904 Digital Diagnostic Tool (DDT) Group. For information and instructions on how to monitor detonation, refer to Operating Manual Form No. SEHS8806, Using The 8C9904 Digital Diagnostic Tool (DDT) Group With The Spark Ignited (SI) Engine Timing Control. If 5 or more bars on the detonation display remain lit, the TCM will retard timing 6°. If the detonation disappears (indicated by 3 or fewer bars lit on the detonation display), timing is advanced 1° per minute until light or no detonation is present (up to the initial timing value).

The timing control records the initial timing value by a two-step timing set up procedure. For set up, see subject, Timing Control Module Test Procedure A.

NOTE: For Timing Control Module Test Procedures A and B and Troubleshooting Procedures TSP1 - TSP7, make reference to 3500 Spark Ignited Electronic Troubleshooting, Form No. SENR4612.

The Timing Control Module (TCM) does the following:

1. Measures engine speed, detonation, and timing.

2. Calculates how much the engine timing should be retarded.

3. Sends signals to the Altronic Interface Box to control engine timing.

4. Determines if the engine should be shutdown due to detonation.

5. Performs system diagnostics.

NOTE: If the TCM determines the engine is experiencing excessive detonation (indicated by 8 or more bars remaining lit on the detonation display of the 8C9904 DDT AFTER the timing is retarded 6°) or if any system faults are present, It sends a signal to a relay in the Junction Box to de-energize the Gas Shutoff Valve (GSOV). At the same time, a separate signal is sent to external switchgear to indicate the engine has been shutdown.

The TCM also performs system diagnostics and displays the diagnostic status on 9 LEDs located on the front cover. In addition, the TCM sends engine speed, timing, detonation level, and diagnostic codes data to the 8C9904 Digital Diagnostic Tool.

Diagnostic Lights On The Timing Control Module

NOTE: All diagnostic lights should turn on when the engine is powered up, This is a lamp test.

Diagnostic lights are provided for troubleshooting and monitoring engine conditions. The lights should indicate what part of the system needs investigating and possible replacement.

Control On (Green): This light should be on when the Timing Control Module has electrical power to it. If the light is not on, the control does not have electrical power or it is defective and needs replacement.

Detonation Retarded Timing (Yellow): This light comes on when the timing has been retarded by the Timing Control Module because of engine detonation. This light can come on occasionally without problems. But if this light comes on for more than 10 Minutes, check for Proper air/fuel ratio settings (exhaust oxygen level).

Detonation Engine Shutdown (Red): This light comes on when the engine has been shutdown because of detonation. The reasons for the engine being in detonation needs to be identified. To reset this light, turn the Engine Control Switch (ECS) on the control panel to the OFF/RESET position. For Junction Box installations, put the optional start/stop switch in the STOP position.

Magneto Out Of Calibration (Red): This light comes on when the engine has been shutdown because the magneto has not been calibrated (timed) using the DDT service tool. To calibrate the magneto, see subject, Magneto Timing. To reset this light, turn the Engine Control Switch (ECS) on the control panel to the OFF/RESET position. For Junction Box installations, put the optional start/stop switch in the STOP position.

No Right Hand Detonation Sensor Signal (Red): This light comes on when the engine has been shutdown because the Timing Control Module is not getting a valid signal from the right bank detonation sensor. Check the connector and the wiring to the sensor. If they are good replace the detonation sensor. To reset this light, turn the Engine Control Switch (ECS) on the control panel to the OFF/RESET position. For Junction Box installations, put the optional start/stop switch in the STOP position.

No Left Hand Detonation Sensor Signal (Red): This light comes on when the engine has been shutdown because the Timing Control Module is not getting a valid signal from the left bank detonation sensor. Check the connector and the wiring to the sensor. If they are good replace the detonation sensor. To reset this light, turn the Engine Control Switch (ECS) on the control panel to the OFF/RESET position. For Junction Box installations, put the optional start/stop switch in the STOP position.

No Speed Sensor Signal (Red): This light comes on when the engine has been shutdown because the Timing Control Module is not getting a valid signal from the engine speed sensor. Check the speed sensor adjustment to make sure it is backed out 1/2 turn. Then check the wiring to the sensor. If the wiring is good, replace the speed sensor (5N9292). To reset this light, turn the Engine Control Switch (ECS) on the control panel to the OFF/RESET position. For Junction Box installations, put the optional start/stop switch in the STOP position.

No Crank Angle Sensor Signal (Red): This light comes on when the engine has been shutdown because the Timing Control Module is not getting a valid signal from the engine crank angle sensor. Check the speed sensor adjustment to make sure it is backed out 1/2 turn. Then check the wiring to the sensor. If the wiring is good, replace the speed sensor (5N9292). To reset this light, turn the Engine Control Switch (ECS) on the control panel to the OFF/RESET position. For Junction Box installations, put the optional start/stop switch in the STOP position.

No Magneto Interface Signal (Red): This light comes on when the engine has been shutdown because the Timing Control Module does not receive an ignition pulse signal from the Altronic Interface Box. Check the wiring from the Altronic Interface Box to the Timing Control Module. If the wiring is good, replace the Altronic Interface Box. To reset this light, turn the Engine Control Switch (ECS) on the control panel to the OFF/RESET position. For Junction Box installations, put the optional start/stop switch in the STOP position.

No Communication Signal (Red): This light comes on only when when the engine is being powered up.

Engine Monitoring and Shutdown Protection

The SI engine uses one of three systems to monitor engine parameters and provide engine shutdown protection: Junction Box (SI-ETS), Junction Box (SI-ETR), or a Control Panel (Status-Timing).

Junction Box (SI-ETS)

ETS Junction Box - Oil Pressure, Water Temperature, Overspeed (Shown With Door Open)
(1) Terminal strips (TS). (2) Junction box. (3) Wiring harness. (4) Annunciator. (5) Overspeed switch.

ETS Junction Box (as seen from rear)
(6) Oil pressure switch.

The Junction Box (SI-ETS) is used on non-DC powered engines to monitor engine oil pressure, coolant temperature, inlet air temperature and engine overspeed conditions. The Junction Box (SI-ETS) is also used to provide shutoff protection for the engine.

The Junction Box (SI-ETS) components include an Altronic Annunciator (4), an energize to shutoff valve (gas shutoff valve), an oil pressure switch (6), a coolant temperature switch and an Altronic Overspeed Switch (5).

The Energize To Shutdown (ETS) system requires a mechanically latched gas shutoff valve (GSOV) that is energized in order for the engine to be shutoff.

When a fault signal is detected, a two stage shutdown sequence is started. First the gas shutoff valve is energized to stop the flow of fuel to the engine. Approximately ten seconds after the gas shutoff valve is energized, the magneto will be grounded during the second stage of the shutdown sequence. When a fault signal is detected, the Engine Status Control Module will display the fault code.

Junction Box (SI-ETR)

ETR Junction Box - Oil Pressure, Water Temperature, Overspeed (Shown With Door Open)
(1) Terminal strips (TS). (2) Wiring harness. (3) Electronic speed switch (ESS). (4) Junction box. (5) Emergency stop switch (ES). (6) Identification foil. (7) Jumpers. (8) Diodes. (9) Slave relays (SR1 & SR2 & SR3). (10) Base. (11) Circuit breakers (CB).

ETR Junction Box (as seen from rear)
(12) Oil pressure switches (OPS1 and OPS2).

The Junction Box (SI-ETR) is used with the SI Timing Control to monitor engine oil pressure, coolant temperature, starter motor overspeed, and engine overspeed conditions. The Junction Box (SI-ETR) is also used to provide shutoff protection for the engine. The Timing Control Module can be remotely mounted from the Junction Box (SI-ETR).

NOTE: If the junction box monitors an overspeed condition, or if the Emergency Stop Push Button is activated, a relay will be energized and ground the magneto. This will cut ignition to the engine.

NOTE: If the junction box monitors a loss of engine oil pressure, or detects a high coolant temperature, a relay will de-energize the gas shutoff valve (GSOV), and will shut the fuel off to the engine.

The junction box components include an electronic speed switch (ESS), a gas shutoff valve (GSOV), three slave relays (SR1, SR2 and SR3), two oil pressure switches (OPS1 and OPS2), and a water temperature switch (WTS).

The Energize To Run (ETR) system requires that slave relay (SR1) and gas shutoff valve (GSOV) remain energized in order for the engine to run.

Control Panel (Status-Timing)

The Control Panel contains the Timing Control Module (TCM), Engine Status Control Module (SCM), an Emergency Stop Push Button (ESPB) and an Engine Control Switch (ECS).

When the engine is to be shutdown, either manually (through a switch) or automatically (through the engine protection system), a two stage shutdown sequence will occur. First, a relay will de-energize the gas shutoff valve (GSOV), and will shut the fuel off to the engine. In the second step of the shutdown sequence a relay will energize and ground the magneto. This will cut ignition to the engine.

The Engine Status Control Module (SCM) is used to monitor engine parameters (oil pressure, coolant temperature, engine overspeed and over cranking of the starter motor), provides an engine protection system (two stage shutdown) and controls normal start/stop functions. When a fault signal is detected, the display is also used to indicate diagnostic codes, to aid in troubleshooting. See the topic, Troubleshooting, Using Diagnostic Code Interpretation in Service Manual Form No. SENR4618 Control Panel (Status-Timing) For 3500 Spark Ignited Engines.

The Timing Control Module (TCM) monitors the engine for detonation through the two detonation sensors. If detonation is detected the timing is retarded. If the engine stays in detonation after the timing has been retarded, the TCM will shut down the engine. The TCM also controls timing based upon engine speed.

An Emergency Stop Push Button (ESPB) is located on the control panel along with the Engine Control Switch (ECS). The ECS has four positions -"Off/Reset, Auto, Manual and Stop".

Location Of Components
(1) Junction box. (2) Timing control module. (3) Emergency stop push button. (4) Engine status control module. (5) Engine control switch.

Inside Of Junction Box Door
(2) SI Timing control module. (3) Emergency stop push button. (4) Engine status control module. (5) Engine control switch. (6) Junction box door.

Engine Status Control Module (SCM)

The Engine Status Control Module is used to monitor engine parameters (oil pressure, coolant temperature, engine overspeed and over cranking of the starter motor), provides an engine protection system (two stage shutdown) and controls normal start/stop functions.

The Engine Status Control Module contains a relay, terminal strips and overspeed verify.

Spark Ignited Timing Control Service Procedure

NOTE: For information and instructions using the DDT, refer to Operating Manual Form No. SEHS8806, Using The 8C9904 Digital Diagnostic Tool (DDT) Group With The Spark Ignited (SI) Engine Timing Control.

To adjust the timing or the magneto needs to be replaced, the DDT (Digital Diagnostic Tool) is needed to time (calibrate) the magneto. DO NOT set the magneto timing without using the DDT (Digital Diagnostic Tool) service tool with the Spark Ignited Timing Control to calibrate the magneto. If the magneto has gotten out of calibration or the calibration is not done, the magneto could turn off and the engine shut down. To set, adjust, or check the magneto timing see subject, Magneto Timing.

Speed Sensitive Timing Maps

Speed Sensitive Timing Map 1 For 1200 RPM Rated Speed

Speed Sensitive Timing Map 2 For 1100 RPM Rated Speed

Speed Sensitive Timing Map 3 For 1000 RPM Rated Speed

Fuel, Air Inlet And Exhaust System

Fuel, Air Inlet And Exhaust System Components (3516 Shown)
(1) Carburetor. (2) Aftercooler. (3) Turbochargers. (4) Balance line between carburetor and gas pressure regulator. (5) Inlet line to carburetor. (6) Exhaust elbow. (7) Exhaust bypass valve. (8) Gas pressure regulator. (9) Gas shutoff valve.

The components of the fuel, air inlet and exhaust system control the quality, temperature and amount of fuel/air mixture available for combustion. These components are the air cleaner, turbochargers, aftercooler (air or watercooled) gas pressure regulator, carburetor, turbulence chamber, distribution channel, an inlet manifold and the intake and exhaust valve mechanisms. Two camshafts one on each side of the block, control the movement of the valve system components.

The inlet manifold is a series of elbows that connect the distribution channel (located in the middle of the engine) to the inlet ports (passages) of the cylinder heads.

There is a separate air cleaner, turbocharger and watercooled exhaust manifold on each side of the engine. The watercooled exhaust manifolds provide a "gas tight" connection from the cylinder heads to the turbochargers. The manifolds also serve as a water manifold by collecting coolant from each cylinder head and directing it to the regulator housing.

All installations have a shutoff valve in the gas supply line. The shutoff valves are either Energized To Run (ETR) or Energized To Shutoff (ETS).

In the (ETR) system, power must be supplied to the shutoff valve to keep the fuel coming to the engine. To stop the engine, the power is removed from the shutoff valve, which interupts the fuel to the engine.

In the (ETS) system, no power is supplied to the shutoff valve to keep the fuel coming to the engine. To stop the engine, power (from the magneto) is supplied to the shutoff valve, which interupts the fuel to the engine. The valve can also be manually operated to stop the engine. After the engine is stopped, manual resetting of the valve is needed to start the engine.

Engine installations using Propane gas have the same system components. In addition a load adjusting valve between the gas pressure regulator and carburetor is used.

Fuel System

Fuel System
(1) Carburetor. (2) Gas supply line to carburetor. (3) Balance line from gas pressure regulator vent to inlet air pressure at carburetor. (4) Gas pressure regulator.

From the main gas supply, fuel enters gas pressure regulator (4) and then goes to the carburetor. The carburetor controls the amount and quality of air-fuel mixture that the engine is allowed to use.

Turbocharged engines have a balance line (3) connected between the carburetor air inlet and the atmospheric vent of gas pressure regulator (4). Balance line (3) directs carburetor inlet air pressure to the upper side of the regulator diaphragm to control gas pressure at the carburetor. The inlet air pressure added to the spring force on the diaphragm, makes sure that gas pressure to the carburetor will always be greater than inlet air pressure, regardless of load conditions. For example, under engine acceleration, the air pressure increases. A small amount of the increased air pressure is directed to gas pressure regulator (4) and moves the control to increase supply gas pressure to the carburetor. By this method, the correct differential pressure between the gas pressure regulator and the carburetor air inlet is controlled. A turbocharged engine will not develop full power with the balance line disconnected.

Gas Pressure Regulator

Regulator Operation
(1) Spring side chamber. (2) Adjustment screw. (3) Spring. (4) Outlet. (5) Valve disc. (6) Main orifice. (7) Main diaphragm. (8) Lever side chamber. (9) Lever. (10) Pin. (11) Valve stem. (12) Inlet.

Gas goes through the inlet (12), main orifice (6), valve disc (5), and the outlet (4). Outlet pressure is felt in the chamber (8) on the lever side of diaphragm (7).

As gas pressure in chamber (8) becomes higher than the force of the diaphragm spring (3) and air pressure in the spring side chamber (1) (atmosphere on naturally aspirated engines; turbocharger boost on turbocharged engines), the diaphragm is pushed against the spring. This turns the lever (9) at pin (10) and causes the valve stem (11) to move the valve disc to close the inlet orifice.

With the inlet orifice closed, gas is pulled from the lever side of chamber (8) through the outlet. This gives a reduction of pressure in the chamber (8). As a result the pressure becomes less than pressure in the spring side chamber. Force of spring and air pressure in the chamber on the spring side moves the diaphragm toward the lever. This turns (pivots) the lever and opens the valve disc, permitting additional gas flow to the carburetor.

When the pressure on either side of the diaphragm is the same, the regulator sends gas to the carburetor at a set amount.

Carburetor

NOTE: Operation of a carburetor with a single air valve is described. Operation of carburetors with dual air valves is the same.

Atmospheric air goes through the air cleaners to the air horn of the carburetor on naturally aspirated engines. On turbocharged engines, the air is pulled through the air cleaners to the turbochargers and then pushed through an aftercooler core to the carburetor air horn. In the air horn, air goes around air valve body (5) and pushes on diaphragm (2) and then goes down through the center of air valve (4), around gas inlet body (6), by throttle plate (10) into the engine.

Fuel goes into the carburetor at the center, through gas inlet body (6). The fuel flows out the top of gas inlet body (6) to mix with the air and then flows around gas inlet body (6), by throttle plate (10) into the engine. Gas valve (7) is connected to air valve (4) and is designed to let the correct amount of fuel into the carburetor at any opening of the air valve between idle and full load. Thus, at low idle, gas valve (7) keeps fuel flow to a minimum and gives a lean air fuel mixture. As the engine speed and load is increased, gas valve (7) lets more fuel flow to give a richer air fuel mixture. When the engine is stopped, spring (3) holds gas valve (7) down against the valve seat in the closed position and no fuel can enter the carburetor. Power screw (8) and plate (9) control fuel inlet at full load conditions when gas valve (7) is at a maximum distance off its seat.

As the engine is started, the intake strokes of the pistons cause a vacuum in the cylinders which causes a low pressure condition below the carburetor. Passages in air valve body (5) connect the low pressure to the upper side of diaphragm (2). At this point, atmospheric pressure pushes up on diaphragm (2) and lifts it against the downward force of spring (3). Air valve (4) is connected to and pulled up by diaphragm (2). At this point, air can push upward against the outside of air valve (4) to help lift it. Gas valve (7) is connected to air valve (4) and is also lifted off its seat to let fuel enter the carburetor. The air pushes up on diaphragm (2) and at the same time goes around the outside and inside of air valve (4) and around gas inlet body (6). As the air passes around gas inlet body (6), it mixes with the fuel. The air fuel mixture then goes down by throttle plate (10), into the distribution channels, to the inlet manifolds and then into the cylinders for combustion.

Carburetor Operation (3512 Carburetor Shown)
(1) Cover. (2) Diaphragm. (3) Spring. (4) Air valve. (5) Air valve body. (6) Gas inlet body. (7) Gas valve. (8) Power screw. (9) Plate. (10) Throttle plate.

2301 Electric Governor

Refer to 2301 Electric Governor Service Manual, Form No. SENR2928 or to 2301A Electric Governor Service Manual, Form No. SENR3585 for additional information.

The 2301 Electric Governor Control System consists of the components that follow: 2301 Electric Governor Control (EGC), Actuator, Magnetic Pickup.

2301 Electric Governor Control (EGC)

The 2301 Electric Governor System gives precision engine speed control. The 2301 control measures engine speed constantly and makes necessary corrections to the engine fuel setting through an actuator connected to the fuel system.

Magnetic Pickup Location
(1) Magnetic pickup. (2) Flywheel housing.

The engine speed is felt by a magnetic pickup. This pickup makes an AC voltage that is sent to the 2301 Control. The 2301 Control now sends a DC voltage signal to the actuator.

EG3P Actuator
(3) Actuator. (4) Actuator lever.

The actuator changes the electrical input from the 2301 Control to a mechanical output that is connected to the fuel system by linkage. For example, if the engine speed is more than the speed setting, the 2301 Control will decrease its output and the actuator will now move the linkage to decrease the fuel to the engine.

Magnetic Pickup

Schematic of Magnetic Pickup
(1) Magnetic lines of force. (2) Wire coils. (3) Gap. (4) Pole piece. (5) Flywheel ring gear.

The magnetic pickup is a single pole, permanent magnet generator made of wire coils (2) around a permanent magnet pole piece (4). As the teeth of the flywheel ring gear (5) cut through the magnetic lines of force (1) around the pickup, an AC voltage is generated. The frequency of this voltage is directly proportional to engine speed.

This engine speed frequency signal (AC) is sent to the 2301 Control Box where a conversion is made to DC voltage. The DC signal is now sent on to control the actuator, and this voltage is inversely proportional to engine speed. This means that if engine speed increases, the voltage output to the actuator decreases. When engine speed decreases, the voltage output to the actuator increases.

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 engine fuel system by mechanical linkage. The governor controls the rate of fuel injected into each of the engine cylinders as needed to adjust 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.

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. qt) 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 increase 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.

Air Inlet And Exhaust Systems

Air flow is the same on both sides of the engine. Clean inlet air from the air cleaners is pulled through the turbocharger compressor housing by a compressor wheel. Rotation of the compressor wheel causes compression of the air and forces it through lines to the aftercooler. The aftercooler lowers the compressed air temperature and provides air at a constant temperature to the carburetor for maximum air/fuel ratio control independent of load on engine. The aftercooler can be watercooled or an air to air type.

From the aftercooler the air goes through the carburetor (where it mixes with gas) and then into a turbulence chamber which keeps the air and fuel properly mixed. A distribution channel is located below the turbulence chamber and has holes in it to direct an equal temperature air/fuel mixture to each cylinder head inlet port. Air flow from the inlet ports into the cylinder combustion chamber is controlled by the intake valves.

There are two intake and two exhaust valves for each cylinder. Make reference to Valve System Components. The intake valves open when the piston moves down on the inlet stroke. Cooled, compressed air from the inlet port is pulled into the cylinder. The intake valves close and the piston starts to move up on the compression stroke. When the piston is near the top of the compression stroke, the magneto sends voltage through a transformer to the spark plug. The spark plug is ignited and combustion starts. The force of combustion pushes the piston down on the power stroke. When the piston moves up again it is on the exhaust stroke. The exhaust valves open and the exhaust gases are pushed through the exhaust port into the exhaust manifolds. After the piston completes the exhaust stroke, the exhaust valves close and the cycle (inlet, compression, power, exhaust) starts again

Exhaust gases from the exhaust manifolds go into the turbine side of each turbocharger and cause a turbine wheel to turn. The turbine wheel is connected to the shaft that drives the compressor wheel. The exhaust gases then go out the exhaust outlet through the exhaust elbow. Changes in engine load and fuel burnt cause changes in rpm of the turbine and compressor wheels. As the turbocharger air pressure boost increases, the air-fuel ratio can change. To increase air and gas densities equally during increased boost, a balance line is connected between the carburetor air inlet and the atmospheric vent of the gas pressure regulator.

Air Inlet System
(1) Turbochargers. (2) Aftercooler. (3) Carburetor. (4) Turbulence chamber. (5) Distribution channel. (6) Cylinder head.

Exhaust System
(7) Exhaust elbow. (8) Exhaust manifold.

Aftercooler

Engine With Watercooled Aftercooler
(1) Aftercooler. (2) Coolant return line. (3) Water pump.

The aftercooler is located in the air lines between the turbochargers and the carburetor. The aftercooler can be an air to air type or it can be watercooled.

Watercooled aftercoolers have a separate circuit cooling system, from the engine jacket water cooling system. Coolant is supplied to water pump (3). The water pump sends coolant through a water line into the bottom of the aftercooler. It then flows through the core assembly and back out of the aftercooler through line (2) to the water pump. A thermostatic valve is installed in line (2) to keep coolant in the aftercooler core assembly at the correct temperature.

Air flow through both cooling systems is as follows. Inlet air from the compressor side of the turbochargers flows into the aftercooler through pipes. This air then passes through the aftercooler core assembly which lowers the temperature. The cooler air goes out of the aftercooler into the carburetor, where fuel is mixed, through the turbulence chamber and distribution channel and up through the elbows to the inlet ports (passages) in the cylinder heads by the intake valves into the combustion chambers.

Distribution Channel And Air Chamber Drain
(4) Drain plug.

All engines have two drain plugs (4) installed. One drain plug is located between the No. 1 and No. 3 cylinder heads, and another plug is located between the last two cylinder heads on the left side of the engine. These plugs can be removed to check for water or coolant in the cylinder block air chamber.

Schematic Of An Air To Air Aftercooler Engine
(5) Actuator with valve positioner. (6) Air cleaner. (7) Carburetor. (8) Turbocharger. (9) Cooling unit.

Air to air aftercooled systems contain a temperature controller that is pressurized to keep dirt and moisture out of it and a bypass valve which consists of an actuator and valve positioner. The temperature controller monitors inlet air temperature and is adjusted to keep it at 43°C (110°F). If the air temperature is too cold, the temperature controller signals an actuator (with pneumatic or gas pressure) to bypass the aftercooler core so air flows from the turbochargers directly into the carburetor.

Typical Air To Air Aftercooled System
(5) Actuator with valve positioner. (6) Air cleaner. (7) Carburetor. (10) Vent cap for temperature controller. (11) Sensing element for temperature controller. (12) Temperature controller.

Temperature Controller Installation
(10) Vent cap. (12) Temperature controller. (13) Pressure relief valve. (14) Pressure reducing valve. (15) Filter.

Schematic Of Instrument Installation For Air To Air Aftercooled Systems

Turbochargers

There are two turbochargers, on the rear of the engine. The turbine side of the turbochargers is fastened to the exhaust manifolds. The compressor side of the turbocharger is connected to the aftercooler.

Turbochargers
(1) Turbocharger. (2) Oil supply line. (3) Oil drain line.

The exhaust gases go into turbine housing (8) and push the blades of turbine wheel (9). This causes the turbine wheel and compressor wheel to turn at up to 70,000 rpm.

Turbocharger (Typical Example)
(4) Compressor wheel. (5) Bearing. (6) Oil inlet. (7) Bearing. (8) Turbine housing. (9) Turbine wheel. (10) Air inlet. (11) Oil outlet.

Clean air from the air cleaners is pulled through the compressor housing air inlet (10) by rotation of compressor wheel (4). The action of the compressor wheel blades causes a compression of the inlet air. This compression gives the engine more power because it makes it possible for the engine to burn additional fuel with greater efficiency.

Maximum rpm of the turbocharger is controlled by the fuel setting, the high idle rpm setting and the height above sea level at which the engine is operated.

Show/hide table

NOTICE

If the high idle rpm or the fuel setting is higher than given in the Fuel Setting Information Fiche (for the height above sea level at which the engine is operated), there can be damage to engine or turbocharger parts. Damage will result when increased heat and/or friction due to the higher engine output goes beyond the engine cooling and lubrication systems abilities. A mechanic that has the proper training is the only one to make the adjustment of fuel setting and high idle rpm setting.

The bearings (5 and 7) in the turbocharger use engine oil under pressure for lubrication. The oil comes in through oil inlet port (6) and goes through passages in the center section for lubrication of the bearings. Then the oil goes out oil outlet port (11) and back to the oil pan.

Exhaust Bypass Valve (Engines With Turbochargers)

Exhaust Bypass Valve Location
(1) Exhaust elbow. (2) Exhaust bypass valve (horizontally mounted). (3) Exhaust bypass control line (air line from carburetor inlet). (4) Turbocharger.

Exhaust bypass valve (2) is installed in exhaust elbow (1). This valve controls the amount of exhaust gases that go through the turbocharger turbine housing and drive the turbine wheel.

Air Line Connection
(3) Exhaust bypass valve control line (air line from exhaust bypass valve). (5) Carburetor.

Exhaust Bypass Valve Operation
(6) Air line connection. (7) Springs. (8) Cover assembly. (9) Poppet valve. (10) Breather location. (11) Base assembly. (12) Diaphragm. (13) Diaphragm retainer.

Poppet Valve (9) is activated directly by a pressure differential between the air pressure (atmosphere) and turbocharger compressor outlet pressure to the carburetor.

One side of the diaphragm (12) in the regulator feels atmospheric pressure through a breather in the top of the regulator. The other side of the diaphragm feels air pressure from the outlet side of the turbocharger compressor through a control line connected to inlet side of the aftercooler. When outlet pressure to the carburetor gets to the correct value, the force of the air pressure on the diaphragm moves the diaphragm which over comes the force of the springs (7) and atmospheric pressure. This opens the valve, and stops exhaust gases from going to the turbine wheel.

Under constant load conditions, the valve will take a set position, permitting just enough gas to go to the turbine wheel to give the correct air pressure to the carburetor.

The Exhaust Bypass Valve is preset at the factory. Adjustments may be necessary due to altitude or changes in ambient temperature conditions.

Valve System Components

Valve System Components
(1) Rocker arm. (2) Bridge. (3) Rotocoil. (4) Valve spring. (5) Push rod. (6) Lifter.

The valve system components control the flow of inlet air and exhaust gases into and out of the cylinders during engine operation.

The crankshaft gear drives the camshaft gears through idlers. Both camshafts must be timed to the crankshaft to get the correct relation between piston and valve movement.

The camshafts have two cam lobes for each cylinder. The lobes operate the valves.

As each camshaft turns the lobes on the camshafts cause lifters (6) to go up and down. This movement makes push rods (5) move rocker arms (1). Movement of the rocker arms makes bridges (2) move up and down on dowels in the cylinder head. The bridges let one rocker arm open and close two valves (intake or exhaust). There are two intake and two exhaust valves for each cylinder.

Rotocoils (3) cause the valves to turn while the engine is running. The rotation of the valves keeps the deposit of carbon on the valves to a minimum and gives the valves longer service life.

Valve springs (4) cause the valves to close when the lifters move down.

Lubrication System

Lubrication System Schematic
(1) Main oil gallery. (2) Left camshaft oil gallery. (3) Piston cooling jet oil gallery. (4) Piston cooling jet oil gallery. (5) Right camshaft oil gallery. (6) Turbocharger oil supply. (7) Sequence valve. (8) Sequence valve. (9) Adapter. (10) Oil filter bypass valve. (11) Oil cooler. (12) Bypass valve. (13) Oil pump relief valve. (14) Engine oil pump. (15) Elbow. (16) Suction bell. (17) Oil filter housing.

This system uses an oil pump (14) with three pump gears that are driven by the front gear train. Oil is pulled from the pan through suction bell (16) and elbow (15) by the oil pump. The suction bell has a screen to clean the oil.

The oil pump pushes oil through oil cooler (11) and the oil filters to oil galleries (1 and 2) in the block. The fin and tube type oil cooler lowers the temperature of the oil before the oil is sent on to the filters.

Bypass valve (12) allows oil flow directly to the filters if the oil cooler becomes plugged or if the oil becomes thick enough (cold start) to increase the oil pressure differential (cooler inlet to outlet) by an amount of 180 ± 20 kPa (26 ± 3 psi).

NOTE: In certain cogeneration models, with high water temperatures, an oil temperature regulator (instead of the oil cooler bypass valve) is used in the line going to the oil filter. When the oil is thick (cold start) the oil temperature regulator lets oil flow directly to the filters. When the oil temperature regulator opens (engine warm) the oil is sent through the oil cooler to the oil filters.

Cartridge type filters are located in oil filter housing (17) at the front of the engine. A single bypass valve is located in the oil filter housing.

Clean oil from the filters goes into the block through adapter (9). Part of the oil goes to the left camshaft oil gallery (2) and part goes to the main oil gallery (1).

The camshaft oil galleries are connected to each camshaft bearing by a drilled hole. The oil goes around each camshaft journal, through the cylinder head and rocker arm housing, to the rocker arm shaft. A drilled hole connects the bores for the valve lifters to the oil hole for the rocker arm shaft. The valve lifters get lubrication each time they go to the top of their stroke.

Main oil gallery (1) is connected to the main bearings by drilled holes. Drilled holes in the crankshaft connect the main bearing oil supply to the rod bearings. Oil from the rear of the main oil gallery goes to the rear of right camshaft gallery (5).

Sequence valves (7 and 8) let oil from main oil gallery (1) go to piston cooling jet oil galleries (3 and 4). The sequence valves open at 140 kPa (20 psi). The sequence valves will not let oil into the piston cooling jet oil galleries until there is pressure in the main oil gallery. This decreases the amount of time necessary for pressure build-up when the engine is started. It also helps hold pressure at idle speed.

Piston Cooling And Lubrication (Typical Example)
(18) Cooling jet.

There is a piston cooling jet (18) below each piston. Each cooling jet has two openings directed at the center of the piston. This helps cool the piston and gives lubrication to the piston pin

Turbochargers
(6) Oil supply lines. (19) Oil drain for left turbocharger. (20) Oil drain for right turbocharger.

Oil lines (6) give oil to the turbochargers. The turbocharger drain lines (19 and 20) are connected to the flywheel housing on each side of the engine.

Oil is sent to the front and rear gear groups through drilled passages in the front and rear housings and cylinder block faces. These passages are connected to camshaft oil galleries (2 and 5).

After the oil for lubrication has done its work, it goes back to the engine oil pan.

Right Front Side Of Engine
(10) Oil filter bypass valve. (17) Oil filter housing. (21) Oil line to filter housing.

Left Front Of Engine
(9) Adapter. (17) Oil filter housing. (22) Oil outlet line from oil filter housing.

Cooling System

3500 SI Engine Schematic Two circuit with two engine driven pumps
(1) Thermostatic valve (coolant temperature for aftercooler). (2) Heat exchanger (aftercooler). (3) Pump - aftercooler circuit (engine driven). (4) Bypass line (aftercooler). (5) Front housing. (6) Aftercooler. (7) Regulator housing. (8) Bypass line (jacket water). (9) Oil cooler. (10) Pump - jacket water / oil cooler circuit (engine driven). (11) Heat exchanger (jacket water / oil cooler).

3500 SI Landfill Engine Schematic Two circuit with two engine driven pumps (requires a large aftercooler / oil cooler heat exchanger).
(1) Thermostatic valve. (2) Aftercooler / oil cooler heat exchanger. (3) Pump - aftercooler / oil cooler circuit (engine driven). (4) Bypass line. (5) Front housing. (6) Regulator housing. (7) Aftercooler. (8) Thermostatic valve (oil temperature). (9) Bypass line. (10) Oil cooler. (11) Pump - jacket water circuit (engine driven). (12) Heat exchanger - jacket water.

3500 SI Cogeneration Engine Schematic Jacket water pump (customer supplied) Three circuit with two engine driven pumps.
(1) Thermostatic valve. (2) Heat exchanger (aftercooler). (3) Pump - aftercooler circuit (engine driven). (4) Bypass line (aftercooler). (5) Front housing. (6) Oil line to oil filter. (7) Aftercooler. (8) Regulator housing. (9) Bypass line (oil cooler). (10) Thermostatic valve (oil temperature). (11) Oil cooler. (12) Pump - oil cooler circuit (engine driven). (13) Pump - jacket water circuit (customer supplied). (14) Heat exchanger (jacket water). (15) Heat exchanger (oil cooler).

3500 SI Cogeneration Engine Schematic Jacket water pump (customer supplied) Two circuit with one engine driven pump (requires a larger aftercooler/oil cooler heat exchanger).
(1) Thermostatic valve (coolant temperature for aftercooler). (2) Aftercooler/oil cooler heat exchanger. (3) Pump - aftercooler/oil cooler circuit (engine driven). (4) Bypass line. (5) Front housing. (6) Regulator housing. (7) Aftercooler. (8) Thermostatic valve (oil temperature). (9) Bypass line. (10) Oil cooler. (11) Pump - jacket water circuit (customer supplied). (12) Heat exchanger - jacket water.

Jacketwater System

Right Side Of Engine (Typical Example)
(1) Water line to front of engine cylinder block. (2) Bypass line. (3) Oil cooler. (4) Water pump.

This system uses a water pump (4) that is driven by the lower front right gear group. Coolant from a radiator or other heat exchanger is pulled into the center of the water pump housing by the rotation of the water pump impeller. The coolant flow is then divided at the water pump outlet. Part of the coolant flow is sent to the front of the cylinder block and part is sent through the engine oil cooler.

NOTE: There is one opening on the pump outlet so that a remote pump can be connected to the system. The remote pump can be used if there is a failure of the water pump on the engine.

Coolant sent to the front of the cylinder block goes through a main distribution manifold to each cylinder water jacket. The main distribution manifold is located just above the main bearing oil gallery in the center of the cylinder block. Some of the coolant goes out the back of the cylinder block and into the adapter housing for the exhaust bypass valve. Flow from the exhaust bypass valve adapter housing is divided. Part of the coolant goes up through the exhaust elbow and part goes up through the turbocharger turbine housings. All coolant flow is then directed into the water cooled exhaust manifolds.

Coolant Flow From Rear Of Engine (Typical Example)
(5) Exhaust elbow. (6) Water line between exhaust elbow and exhaust manifold. (7) Water line from left turbocharger to exhaust manifold. (8) Water line from right turbocharger to exhaust manifold. (9) Left turbocharger. (10) Right turbocharger. (11) Water line to left turbocharger. (12) Water line to right turbocharger.

The coolant sent to the oil cooler goes through the oil cooler and flows into the water jacket of the block at the right rear cylinder. The cooler coolant mixes with the hotter coolant and goes to both sides of the block through the distribution manifolds connected to the water jacket of all the cylinders.

The coolant flows up through the water jackets and around the cylinder liners from the bottom to the top. Near the top of the cylinder liners, where the temperature is the hottest, the water jacket is made smaller. This shelf (smaller area) causes the coolant to flow faster for better liner cooling. Coolant from the top of the liners goes into the cylinder head which sends the coolant around the parts where the temperature is the hottest. Coolant then goes to the top of the cylinder head and out through an elbow one at each cylinder head, into watercooled exhaust manifolds (13) at each bank of cylinders. Coolant goes through the manifolds to the temperature regulator (thermostat) housing.

Regulator housing (14) has an upper and lower flow section, and uses four temperature regulators. The sensing bulbs of the four temperature regulators are in the coolant in the lower section of the housing. Before the regulators open, cold coolant is sent through the lower section of the housing and through the bypass line back to the inlet of the water pump. As the temperature of the coolant increases enough to make the regulators start to open, coolant flow in the bypass line is stopped and coolant is sent through the outlets to the radiator or heat exchanger.

NOTE: The water temperature regulator is an important part of the cooling system. It divides coolant flow between the heat exchanger and internal bypass of the water pump as necessary to maintain the correct temperature. If the water temperature regulator is not installed in the system, there is no mechanical control, and most of the coolant will take the path of least resistance through the bypass. This will cause the engine to overheat in hot weather. In cold weather, even the small amount of coolant that goes through the radiator is too much, and the engine will not get to normal operating temperatures.

Total system coolant capacity will depend on the size of the heat exchanger. Use a coolant mixture of 50 percent pure water and 50 percent permanent antifreeze, then add a concentration of 3 to 6 percent corrosion inhibitor.

Water Temperature Regulator Housings
(2) Bypass line. (13) Watercooled exhaust manifolds. (14) Regulator housing. (15) Water outlet. (16) Housing.

Separate Circuit Aftercooler (SCAC) System

Left Side Of Engine (Typical Example)
(1) Aftercooler. (2) Coolant return line. (3) Coolant inlet line to the aftercooler. (4) Water pump. (5) Thermostatic valve.

Engines with a water cooled aftercooler use a separate circuit aftercooler (SCAC) coolant system, instead of the normal engine jacket water circuit, to cool the air in the aftercooler. With the SCAC system, coolant is supplied from a separate radiator or heat exchanger.

With the engine running and not at operating temperature, the aftercooler coolant circuit is closed. Auxiliary water pump (4) sends coolant through line (3) to aftercooler (1) at approximately 570 liter/m (150 U.S. gpm). Coolant flows up through the core assembly and out of the aftercooler through line (2), thermostatic valve (5) and back to auxiliary water pump (4). As the coolant temperature increases, thermostatic valve (5) opens and coolant flow from the aftercooler core assembly is directed to a radiator or heat exchanger and then back to auxiliary water pump (4). Thermostatic valve (5) will be fully open when the coolant temperature is 32°C (90°F) or 54°C (130°F) depending on the thermostat installed in the valve housing.

NOTE: The water temperature regulator is an important part of the cooling system. It divides coolant flow between the heat exchanger and the internal bypass of the water pump as necessary to maintain the correct temperature. If the water temperature regulator is not installed in the system, there is no mechanical control, and most of the coolant will take the path of least resistance through the bypass. This will cause the engine to overheat in hot weather. In cold weather, even the small amount of coolant that goes through the radiator is too much, and the engine will not get to normal operating temperatures.

NOTE: Certain cogeneration engines do not use thermostats to control jacket water temperature. The engine temperature is controlled externally with a heat exchanger by maintaining the outlet temperature of the steam system. In high water temperature applications the oil cooler is on a separate circuit. A thermostat controls the oil temperature going to the bearings.

Basic Block

Cylinder Block, Liners And Heads

The cylinders in the left side of the block make an angle of 60° with the cylinders in the right side of the block. The main bearing caps are fastened to the block with four bolts per cap.

The cylinder liners can be removed for replacement. The top surface of the block is the seat for the cylinder liner flange. Engine coolant flows around the liners to keep them cool. Three O-ring seals around the bottom of the liner make a seal between the liner and the cylinder block. A filler band goes under the liner flange and makes a seal between the top of the liner and the cylinder block.

The engine has a separate cylinder head for each cylinder. Four valves (two intake and two exhaust), controlled by a push rod valve system, are used for each cylinder. Valve guides without shoulders are pressed into the cylinder heads. The opening for the spark plug is located between the four valves.

There is an aluminum spacer plate between each cylinder head and the block. Coolant goes out of the block through the spacer plate and into the head through eight openings in each cylinder head face. Grommets the width of the spacer plate prevent coolant leakage. Gaskets seal the oil drain passages between the head, spacer plate and block.

Left Side Of 3516 Engine
(1) Covers for camshaft and valve lifter inspection. (2) Covers for crankshaft main and rod bearing inspection.

Covers (1) allow access to the camshafts and valve lifters.

Covers (2) allow access to the crankshaft connecting rods, main bearings and piston cooling jets. With covers removed, all the openings can be used for inspection and service.

Pistons, Rings And Connecting Rods

The aluminum pistons have an iron band for the top two rings. This helps reduce wear on the compression ring grooves. The pistons have three rings; two compression rings and one oil ring. All the rings are located above the piston pin bore. The oil ring is a standard (conventional) type. Oil returns to the crankcase through holes in the oil ring groove. The top two compression rings are also the standard (conventional) type.

The connecting rod has a taper on the pin bore end. This gives the rod and piston more strength in the areas with the most load. Four bolts set at a small angle hold the rod cap to the rod. This design keeps the rod width and weight to a minimum, so that the largest possible rod bearing (and crank journal) can be used and the rod can still be removed through the top of the liner bore.

Crankshaft

The crankshaft changes the combustion forces in the cylinder into usable rotating torque which powers the engine. A vibration damper of the fluid type is used at the front of the crankshaft to reduce torsional vibrations (twist on the crankshaft) that can cause damage to the engine.

The crankshaft drives a group of gears on the front and rear of the engine. The gear group on the front of the engine drives the oil pump, water pump, fuel transfer pump, governor or governor actuator and two accessory drives. The gear group on the rear of the engine drives the camshafts.

Lip seals and wear sleeves are used at both ends of the crankshaft for easy replacement and a reduction of maintenance cost. Pressure oil is supplied to all main bearings through drilled holes in the webs of the cylinder block. The oil then flows through drilled holes in the crankshaft to provide oil to the connecting rod bearings. The crankshaft is held in place by five main bearings on the 3508, seven main bearings on the 3512, and nine main bearings on the 3516. A thrust plate at either side of the center main bearing controls the end play of the crankshaft.

Camshafts

The 3512 and 3516 have two camshafts per side that are doweled and bolted together to make a camshaft group. Each 3516 camshaft group is supported by nine bearings and is driven by the gears at the rear of the engine. Each 3512 camshaft group is supported by seven bearings and is driven by the gears at the rear of the engine. The 3508 has one camshaft per side. Each camshaft is supported by five bearings and is driven by the gears at the rear of the engine.

As the camshaft turns, each lobe moves a lifter assembly. There are two lifter assemblies for each cylinder. Each lifter assembly moves a push rod and two valves (either intake or exhaust). The camshafts must be in time with the crankshaft. The relation of the cam lobes to the crankshaft position cause the valves in each cylinder to operate at the correct time.

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 starting motor. (2) Relay valve. (3) Oiler.

The air starting motor 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 nondetergent 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). Higher pressures can cause safety problems.

Typical Air Start Installation
(4) Air start control valve.

The air from the supply goes to relay valve (2). The starter control valve (4) is connected to the line before the relay valve (2). The flow of air is stopped by the relay valve (2) until starter control valve (4) is activated. The air from starter control valve (4) 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 (2). The air activates relay valve (2) which opens the supply line to the air starting motor.

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

The flow of air goes through oiler (3) where it picks up lubrication oil for the air starting motor.

The air with lubrication oil 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 starter pinion (8). Pinion (8) retracts under this condition. This prevents damage to the motor, pinion (8) or flywheel gear.

When starter control valve (4) is released, the air pressure and flow to piston (10) behind starter pinion (8) is stopped, piston spring (11) retracts pinion (8). Relay valve (2) stops the flow of air to the air starting motor.

Electrical System

The electrical system has three separate circuits: the charging circuit, the starting circuit and the low amperage circuit. Some of the electrical system components are used in more than one circuit. The battery (batteries), circuit breaker, ammeter, cables and wires from the battery are all common in each of the circuits.

The charging circuit is in operation when the engine is running. An alternator makes electricity for the charging circuit. A voltage regulator in the circuit controls the electrical output to keep the battery at full charge.

The starting circuit is in operation only when the start switch is activated.

The low amperage circuit and the charging circuit are both connected to the same side of the ammeter. The starting circuit connects to the opposite side of the ammeter.

Charging System Components

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NOTICE

Never operate the alternator without the battery in the circuit. Making or breaking an alternator connection with heavy load on the circuit can cause damage to the regulator.

Alternator (Delco-Remy)

Delco-Remy Alternator
(1) Regulator. (2) Roller bearing. (3) Stator winding. (4) Ball bearing. (5) Rectifier bridge. (6) Field winding. (7) Rotor assembly. (8) Fan.

The alternator is driven by belts from the crankshaft pulley. This alternator is a three phase, self-rectifying charging unit, and the regulator is part of the alternator.

This alternator design has no need for slip rings or brushes, and the only part that has movement is the rotor assembly. All conductors that carry current are stationary. The conductors are: the field winding, stator windings, six rectifying diodes, and the regulator circuit components.

The rotor assembly has many magnetic poles like fingers with air space between each opposite pole. The poles have residual magnetism (like permanent magnets) that produce a small amount of magnet-like lines of force (magnetic field) between the poles. As the rotor assembly begins to turn between the field winding and the stator windings, a small amount of alternating current (AC) is produced in the stator windings from the small magnetic lines of force made by the residual magnetism of the poles. This AC current is changed to direct current (DC) when it passes through the diodes of the rectifier bridge. Most of this current goes to charge the battery and to supply the low amperage circuit, and the remainder is sent on to the field windings. The DC current flow through the field windings (wires around an iron core) now increases the strength of the magnetic lines of force. These stronger lines of force now increase the amount of AC current produced in the stator windings. The increased speed of the rotor assembly also increases the current and voltage output of the alternator.

The voltage regulator is a solid state (transistor, stationary parts) electronic switch. It feels the voltage in the system, and switches on and off many times a second to control the field current (DC current to the field windings) to the alternator. The output voltage from the alternator will now supply the needs of the battery and the other components in the electrical system. No adjustment can be made to change the rate of charge on these alternator regulators.

Alternator (Bosch)

The alternator is driven by from the crankshaft pulley. This alternator is a three phase, self-rectifying charging unit, and the regulator is part of the alternator.

Bosch Alternator
(1) Fan. (2) Stator winding. (3) Field winding. (4) Regulator. (5) Ball bearing. (6) Roller bearing. (7) Rotor. (8) Rectifier assembly.

The rotor assembly has many magnetic poles like fingers with air space between each opposite pole. The poles have residual magnetism (like permanent magnets) that produce a small amount of magnet-like lines of force (magnetic field) between the poles. As the rotor assembly begins to turn between the field winding and the stator windings, a small amount of alternating current (AC) is produced in the stator windings from the small magnetic lines of force made by the residual magnetism of the poles. This AC current is changed to direct current (DC) when it passes through the diodes of the rectifier bridge. Most of this current goes to charge the battery and to supply the low amperage circuit, and the remainder is sent to the field windings. The DC current flow through the field windings (wires around an iron core) now increases the strength of the magnetic lines of force. These stronger lines of force now increase the amount of AC current produced in the stator windings. The increased speed of the rotor assembly also increases the current and voltage output of the alternator.

Alternator (Nippondenso)

The alternator is driven by belts from the crankshaft pulley. The alternators are brushless and contain an internally mounted, solid state voltage regulator.

Nippondenso Alternator Components
(1) Fan. (2) Front frame assembly. (3) Stator assembly. (4) Rotor assembly. (5) Field winding (coil) assembly. (6) Regulator assembly. (7) Condenser (suppression capacitor). (8) Rectifier assembly. (9) Rear frame assembly.

The major components of the alternator are stator assembly (3), rectifier assembly (8), field winding (5), rotor assembly (4), regulator assembly (6) and condenser (suppression capacitor) (7).

Stator assembly (3) consists of a stator core and coils. As the rotor turns, its varying magnetic field causes the stator coil to produce three-phase alternating current (AC).

Rectifier assembly (8) contains three positive diodes and three negative diodes to form the full wave rectifier which is connected to the stator assembly. The 50A alternator has four positive and four negative diodes. Rectifier assembly (8) changes three-phase AC to DC and provides excitation current through three exciter diodes.

Field winding (5) is a stationary coil assembly that provides the magnetic field for the rotor assembly. Rotor assembly (4) provides the north and south poles which cut the magnetic field between the rotor field winding and the stator assembly. The north and south poles are separated by non-magnetic ring (12). Regulator assembly (6) controls alternator output. It is mounted inside the rear frame assembly.

Condenser (7) serves as a suppression capacitor. It protects the alternator diodes from voltage spikes. It also suppresses radio and electronic interference. Condenser (7) also contains a resistor which is in series with the condenser. The condenser is mounted in the rear frame assembly on top of the regulator assembly.

Starter System Components

Starter Solenoid

A solenoid is an electromagnetic switch that does two basic operations.

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

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

Typical Solenoid Schematic

The solenoid has windings (one or two sets) 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 starter 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 windings, and the rest flows through the pull-in windings to 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.

Starter Motor

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

Starter Motor Cross Section (Typical Illustration)
(1) Field. (2) Solenoid. (3) Clutch. (4) Pinion. (5) Commutator. (6) Brush assembly. (7) Armature.

The starter motor has a solenoid. When the start switch is activated, electricity will flow through the windings of the solenoid. The solenoid core will now move to push the starter pinion, by a mechanical linkage to engage 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 starter motor. When the circuit between the battery and the starter motor is complete, the pinion will turn the engine flywheel. A clutch gives protection for the starter motor so that the engine, when it starts to run, can not turn the starter motor too fast. When the start switch is released, the starter pinion will move away from the flywheel ring gear.

Other Components

Circuit Breaker

The circuit breaker is a switch that opens the battery circuit if the current in the electrical system goes higher than the rating of the circuit breaker.

A heat activated metal disc with a contact point completes the electric circuit through the circuit breaker. If the current in the electrical system gets too high, it causes the metal disc to get hot. This heat causes a distortion of metal disc which opens the contacts and breaks the circuit. A circuit breaker that is open can be reset after it cools. Push the reset button to close the contacts and reset the circuit breaker.

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NOTICE

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

Circuit Breaker Schematic
(1) Reset button. (2) Disc in open position. (3) Contacts. (4) Disc. (5) Battery circuit terminals.

Magnetic Pickup

Schematic of Magnetic Pickup
(1) Magnetic lines of force. (2) Wire coils. (3) Gap. (4) Pole piece. (5) Flywheel ring gear.

Magnetic Switch

A magnetic switch (relay) is used for the starter solenoid circuit. Its operation electrically, is the same as the solenoid. Its function is to reduce the low current load on the start switch and control low current to the starter solenoid.

Water Temperature Contactor Switch

The contactor switch for water temperature is installed in the regulator housing. 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 contactor when the coolant temperature is too high. The element must be in contact with the coolant to operate correctly. If the reason for the engine being too hot is caused by low coolant level or no coolant, the contactor switch will not operate.

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

Air Inlet Temperature Switch

The contactor switch for air inlet temperature is installed in the inlet air manifold. No adjustment to the temperature range of the contactor can be made. The element feels the temperature of the inlet air and then operates the micro switch in the contactor when the inlet air temperature is too high. The element must be in contact with the inlet air to operate correctly.

The contactor switch is normally connected to the electric shutoff system to stop the engine. The switch can also be connected to an alarm system. When the temperature of the inlet air lowers again to the operating range, the contactor switch opens automatically.