lekq7511 g3400 engine basics

G3400EngineBasics

LEKQ7511 8-97

G3400 Engine BasicsEngine Design

G3406G3408G3412

Ignition System – MagnetoSpark Plug AdapterSpark Plug and Transformer

Ignition System – ElectricEIS Control ModuleIgnition TransformersEngine Sensors

Fuel, Air Inlet and Exhaust SystemsEngine BasicsFuel SystemAir Inlet and Exhaust Systems

Lubrication SystemOil Flow Through the Oil Cooler and Oil FiltersOil Flow in the Engine (G3406)Oil Flow in the Engine (G3408 & G3412)

Cooling SystemJacketwater System (G3406)Jacketwater System (G3408 & G3412)

Basic BlockCylinder Block, Liners and HeadsPistons, Rings and Connecting RodsCrankshaftCamshaftVibration Damper

Electrical SystemEngine Electrical SystemCharging System ComponentsGrounding Practices

Starting SystemsElectricAir Start

Engine Monitoring and Shutdown ProtectionJunction BoxEngine Start/Stop PanelDC Control Panel for Gas Engine ChillerDC Control Panel for Gas Engine Chiller (Inside

View)

Abbreviations and Symbols

Engine Design

G3406

Cylinder And Valve Location

Bore .....................................137.2 mm (5.40 in.)

Stroke...................................152.4 mm (6.00 in.)

Displacement ...................14.6 liter (893 cu. in.)

Number and Arrangement of Cylinders ..............................................6, In Line

Valves per Cylinder........................................... 4

Rotation of Crankshaft(when seen from flywheel end).....................................counterclockwise

Ignition System Type.........solid state magneto

Rotation of Magneto(when seen from drive end) ..............clockwise

Firing Order ...................................1, 5, 3, 6, 2, 4

Compression Ratios Available ...............................9.4:1, 10.3:1, 11.6:1

Combustion....................................spark ignited

Note: Front end of engine is opposite toflywheel end.

No. 1 cylinder location ................................front

G3408


Bore .....................................137.2 mm (5.40 in.)

Stroke...................................152.4 mm (6.00 in.)

Displacement ....................18 liter (1099 cu. in.)

Number and Arrangement of Cylinders ..................................................65° V-8

Valves per Cylinder........................................... 4


Ignition System Type ..........Electronic IgnitionSystem (EIS) or solid state magneto

Rotation of Magneto(when seen from flywheel end) ....clockwise

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

Compression Ratios Available .................................8.5:1, 9.7:1, 11.1:1



Left side and right side of engine are as seenfrom flywheel end.

No. 1 cylinder is the front cylinder on the leftside.

No. 2 cylinder is the front cylinder on the rightside.

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G3412


Bore ......................................137.2 mm (5.40 in)

Stroke....................................152.4 mm (6.00 in)

Displacement ......................27 liter (1649 cu in)

Number of Cylinders ...................................V-12

Arrangement of Cylinders ...............65 degrees

Valves per Cylinder............................................4


Ignition System Type ..........Electronic IgnitionSystem (EIS) or solid state magneto

Rotation of Magneto(when seen from flywheel end).....................................counterclockwise

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

Compression Ratios Available .....................8.5:1, 9.7:1, 11.1:1, 11.4:1



Left side and right side of engine are as seenfrom flywheel end.

No. 1 cylinder is the front cylinder on the leftside.

No. 2 cylinder is the front cylinder on the rightside.

Ignition System –Magneto

Figure 1: Solid State Magneto(Altronic)(1) Alternator section. (2) Electronic firing section.

The Altronic magneto is made of a permanentmagnet alternator section (1) and breakerlesselectronic firing section (2). See Figure 1.There are no brushes or distributor contacts.

The engine turns magneto drive tang (7). SeeFigure 2. The drive tang turns alternator (3),speed reduction gears (5) and rotating timerarm (9). As the alternator is turned it providespower to charge energy storage capacitor (8).There are separate pick-up coils (6) and SCR(silicon controlled rectifier) solid stateswitches (10) for each engine cylinder. Thetimer arm passes over pick-up coils (6) insequence. The pick-up coils turn on solid stateswitches (10) which release the energy storedin capacitor (8). This energy leaves themagneto through output connector (11). Theenergy travels through the wiring harness tothe ignition coils where it is transformed tothe high voltage needed to fire the sparkplugs.

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Spark Plug Adapter

Figure 3: Spark Plug Adapter(1) Adapter. (2) Seal. (3) Cylinder head.

The spark plug adapter (1) is mounted in thecylinder head (3). See Figure 3. Seal (2) stopsany type of leakage between the adapter andthe cylinder head. The adapter extendsupward through a hole in the valve cover.

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Figure 2: Cross Section Of Solid State Magneto (Altronic)(3) Alternator. (4) Vent. (5) Speed reduction gears. (6) Pick-up coil. (7) Drive tang. (8) Energy storage capacitor. (9) Rotating timer arm. (10) SCR Solid state switch. (11) Output connector.

Spark Plug And Transformer

Figure 4: Spark Plug And Transformer (G3406)(1) Transformer. (2) Wire assembly. (3) Rubber boot(part of wire assembly). (4) Seal. (5) Spark plug.

When the Altronic magneto is used,transformer (1) is mounted on the valve cover.See Figures 4 and 5. Wire assembly (2) is thehigh tension lead to ignite the spark plug (5).Rubber boot (3) is part of wire assembly (2).The boot forms a seal between the adapterand valve cover to keep dirt, water or otherforeign material out of the adapter. Seal (4)prevents crankcase vapors and oil fromentering the adapter.

NOTICEBoth the wire assembly and seal must beinstalled on all cylinders when running theengine. Failure to do this may allow a sparkfrom the exposed wire assembly to ignitecrankcase vapors. Engine damage couldresult.

The ignition transformer (Figure 6) causes anincrease of the magneto voltage. This isneeded to send a spark (impulse) across theelectrodes of the spark plugs. For goodoperation, the connections (terminals) mustbe clean and tight. The negative transformerterminals, with (–) mark, for each transformerare connected together and to ground. Thewiring diagrams (Figure 7) show how all wiresare to be connected to the plug connection atthe magneto.

Figure 5: Spark Plug and Transformer (G3408 & G3412)(Altronic)(1) Transformer. (2) Wire assembly. (3) Rubber boot(part of wire assembly). (4) Seal. (5) Spark plug.

Figure 6: Ignition Transformer.

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G3408 Engine

G3412 Engine

Figure 7: Wiring Diagrams(1) Spark plug. (2) Transformer. (3) Magneto plugconnector.

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G3406 Engine

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Ignition System –ElectronicThe Caterpillar Electronic Ignition System(EIS) is designed to replace the traditionalmagneto ignition system. The ElectronicIgnition System eliminates the magneto andother components that were subject tomechanical wear. It also provides increasedengine diagnostic and troubleshootingcapabilities.

The Electronic Ignition System uses onecontrol module to handle many applicationsand many engine types. This is achieved byallowing the operator to change keyparameters “on–sight”. These programmableparameters are referred to as CustomerSpecified Parameters and may be set orchanged using the Digital Diagnostic Tool(DDT). The DDT is available as a read-only orfully programmable diagnostic tool. Thevalues programmed into the system are storedin the EIS Control Module memory. Thisallows the operator to tailor the ignitionsystem operation with a single service tool.

The DDT (Digital Diagnostic Tool) servicetool is used to program Customer SpecifiedParameters, monitor engine functions, anddisplay engine diagnostics. The DDT canmonitor engine speed, engine timing anddetonation levels.

For additional information on programmingparameters and troubleshooting diagnosticcodes, refer to Electronic Troubleshooting,G3400 Engines, SENR6335.

The EIS control module also has the ability todiagnose and store system problems andpotential transformer secondary circuitproblems. When a problem is detected, adiagnostic code is generated and can bedisplayed on the DDT. The stored systemproblem code is reset when the system resetbutton is pushed.

The EIS system monitors engine operationand distributes power to the cylindertransformers, to provide the best engineperformance at all engine speeds. It alsoprotects the engine from damage caused by

detonation. Within specified limits, control ofengine timing (retarding) is infinitely variable.

The Electronic Ignition System providesdetonation protection and precision sparkcontrol for each cylinder. Detonation iscontrolled as it occurs and timing is retardedonly as much and as long as necessary toprevent engine damage. The EIS systemallows improved operation, economy andlower emission levels. The system consists ofthree basic groups: the control module,ignition transformers and sensors.

EIS Control Module

Figure 8: Ignition System Components(1) Spark plug. (2) Ignition transformer. (3) Valve cover.(4) Wiring harness. (5) Electronic Ignition Systemcontrol module.

The EIS Control Module (5) is a sealed unitwith no serviceable parts (Figure 8). Thecontrol module monitors engine operationthrough a series of sensors. The sensors areconnected to the module through wiringharnesses (4) routed inside the engine block.

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The control module uses input from thesensors and the control panel settings todetermine ignition timing. The control moduleprovides system diagnostics and also suppliesvoltage to the ignition transformers (2) whichstep up the voltage to fire the spark plugs (1).The valve cover (3) acts as a ground for theignition transformer.

Engine timing is controlled by the EIS ControlModule. It is based on the desired enginetiming, customer specified parameters(programmed by the operator) and theconditions in which the engine operates. Theengine operator can change the maximumadvanced timing, the speed timing maps andload timing maps using the Digital DiagnosticTool (DDT). The EIS Control Moduleautomatically adjusts the engine timingaccording to the engine operating conditions,as determined by information from the enginespeed/timing sensor, manifold air pressuresensor, and detonation sensors.

The EIS Control Module has up to 16 ignitionoutputs to the ignition transformers. It alsouses sensors and internal circuitry to monitorthe system components. If a problem developsin a component or harness, the control willsense the problem and notify the operator bycreating a diagnostic code.

Ignition TransformersEach cylinder has an ignition transformerlocated under the cylinder valve cover. TheEIS Control Module sends a pulse to theprimary coil of the ignition transformer toinitiate combustion in each cylinder. Thetransformer steps up the voltage to create anarc across the spark plug gap. The sparkcreated by the arc, ignites the gas in thecylinder. On engines equipped with EIS, thecylinder valve cover acts as the ground for theignition transformer. Care should be exercisedwhen working on the engine with a valvecover removed. Always disconnect the primarylead to the transformer when a valve cover isremoved.

The ignition harness connects the EIS ControlModule to the individual ignitiontransformers. The ignition harness is routedinside the engine alongside the camshaft.

Engine SensorsEngine sensors provide information to the EISControl Module that allow the module tocontrol the engine as efficiently as possibleover a wide range of operating conditions.

Detonation SensorsThe Detonation Sensors (RHDS and LHDS)monitor the engine for excessive detonation(vibration). One sensor is mounted in thecenter of each cylinder bank. The sensorproduces a voltage signal proportional toengine detonation. This information isprocessed by the EIS Control Module todetermine detonation levels and changesengine timing as needed.

Speed/Timing SensorThe Speed/Timing Sensor provides accuratespark timing information for the controlmodule. A speed/timing ring, mounted on therear, left camshaft, provides the signal patterndetected by the sensor and read by the controlmodule. The control module determinesengine speed and timing position from thesensor signal.

Manifold Air Pressure Sensor (Load Sensor)The Manifold Air Pressure Sensor providesengine load information to the EIS ControlModule. The sensor is connected to the inletmanifold. The information is processed by thecontrol module to determine engine timingand diagnostics.

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Fuel, Air Inlet andExhaust Systems

Engine BasicsOn a four-stroke gas engine during the intakestroke, a change of fuel and air (mixed outsidethe combustion chamber in the carburetor) isdrawn (NA) or forced (TA) through the intakevalve (Figure 9). This mixture of fuel and air iscompressed on the compression stroke and isthen ignited by a spark. This spark isgenerated and timed by either a magneto orthe Electronic Ignition System (EIS). Thepiston is then forced downward, creating thepower stroke, toward bottom dead center bythe expanding gases. On the exhaust stroke,the burned gases are pushed out of thecylinder through the exhaust valve as thepiston travels back toward top dead center.

Diesel engines, like natural gas engines,operate in a slightly different way, althoughthe four strokes are the same. On the intakestroke, only air is drawn or forced into thecompression chamber. On the compressionstroke, the air is compressed and thereforeheated; just before the piston reaches top deadcenter, fuel is injected under high pressure.The fuel-air mixture will ignite by itself at thebeginning of the power stroke.

Diesel engines are typically limited by theircapabilities to carry structural load with peakpressures up to 10 335 kPa (1500 psi). Gas

engines are limited by their capability to carrythermal load-high exhaust temperatures.

The gas engine runs with higher exhausttemperatures because it runs with a constantair-fuel ratio at any load. The diesel engineruns with an excess amount of air at any load.Only the amount of fuel burned increases withthe load. This additional air also cools thecharge in diesel engines.

In addition to components shown in thediagram, (Figure 10) some installations have ashut-off valve attachment in the supply line forthe gas. The valve is electrically operated fromthe ignition system and can also be manuallyoperated to stop the engine. After the engineis stopped, manual setting is needed to startthe engine.

Engine installations using dual fuel havesystem components the same as illustratedabove. In addition, dual fuel engines have avacuum regulator and a load adjusting valve.These additional components permit anadjustment to be made for differences in BTUcontent of the gas being used. Dual fuelengines will switch from one fuel to anotherautomatically, but engine timing must beadjusted manually at the time of switchover.

Changes in engine load and fuel burnt causechanges in rpm of the turbine wheels andimpellers of the turbocharger (5).

When the turbocharger gives a pressure boostto the inlet air, the temperature of the air goesup. A water cooled aftercooler (8), is installed

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Figure 9: Four-stroke Process.

between the carburetor (3) and the air inletmanifold (9). The aftercooler causes areduction of air temperature from theturbocharger.

Fuel System

Low Pressure Carburetor System

Figure 11: (1) Gas pressure regulator (2) Gas inlet line. (3) Balance line.

Figure 12: (4) Low pressure carburetor. (5) Air cleaner.(6) Turbocharger.

From the main gas supply line, gas (CC)enters the gas pressure regulator (1). SeeFigures 11-13. The gas pressure regulator isadjusted to provide a flow of fuel, at lowpressure (DD), to the engine gas inlet line (2).As the compressor wheels of the turbocharger(6) rotate, fuel (at low pressure) is drawnthrough the fuel inlet line to the carburetor(4). The carburetor is located between the aircleaner (5) and the compressor side of theturbocharger. The carburetor mixes the fuelwith intake air (EE) from the air cleaner. Theair/fuel mixture (BB) is pulled into the

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Figure 10: Gas, Air Inlet And Exhaust System With Turbocharger(1) Gas pressure regulator. (2) Balance line. (3) Carburetor. (4) Air cleaner. (5) Turbocharger. (6). Gas supply. (7) Governor. (8) Aftercooler. (9) Air inlet manifold. (10) Cylinder. (11) Exhaust bypass. (12) Exhaust manifold.

turbocharger, compressed and sent throughthe throttle group to the aftercooler (9). Thethrottle group is connected by a linkage to thegovernor (8) and controls the flow of theair/fuel mixture into the intake plenum. Theair/fuel mixture in the intake plenum entersthe cylinder (11) through the cylinder inletvalves where it is compressed and ignited bythe spark plug.

Turbocharged engines have a balance line (3)connected between the carburetor air inletand the atmospheric vent of gas pressureregulator. The balance line directs carburetorinlet air pressure to the upper side of theregulator diaphragm to control gas pressure atthe carburetor. The inlet air pressure added tothe spring force on the diaphragm, makessure that gas pressure to the carburetor willalways be greater than inlet air pressure,regardless of load conditions. For example,under engine acceleration, the air pressureincreases. A small amount of the increased airpressure is directed to gas pressure regulatorand moves the control to increase supply gaspressure to the carburetor. By this method,

the correct differential pressure between thegas pressure regulator and the carburetor airinlet is controlled. A turbocharged engine willnot develop full power with the balance linedisconnected.

Engines have a gas pressure valve assemblylocated in the fuel inlet line. The gas pressurevalve assembly is used to adjust emissionlevels at full load, rated speed.

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Figure 13: Gas, Air Inlet And Exhaust System With Turbocharger (Low Pressure)(AA) Exhaust gas. (BB) Air & gas to cylinders. (CC) Gas supply. (DD) Low pressure gas. (EE) Air inlet. (1) Gas pressure regulator. (2) Gas inlet line. (3) Balance line. (4) Carburetor. (5) Air cleaner. (6) Turbocharger. (7) Gas supply. (8) Governor. (9) Aftercooler. (10) Air inlet manifold. (11) Cylinder. (12) Differential pressure regulator.(13) Exhaust manifold.

Gas Pressure RegulatorRegulator for the pressure of the fuel is on theleft side of the engine. Adjustment of theregulator is made by turning the adjustmentscrew (4). See Figure 14.

Figure 14: Regulator Operation(1) Spring side chamber. (2) Spring. (3) Locknut. (4) Adjustment screw. (5) Balance line. (6) Outlet. (7)Main diaphragm. (8) Lever side chamber. (9) Lever. (10)Pin. (11) Valve stem. (12) Inlet.

Gas goes through the inlet (12), main orifice,valve disc, and the outlet (6). Outlet pressureis felt in the chamber (8) on the lever side ofdiaphragm (7).

As gas pressure in the lever side chamberbecomes higher than the force of thediaphragm spring (2) and air pressure in thespring side chamber (1) [turbocharger boostfrom balance line (5)] the diaphragm (7) ispushed against the spring. This turns thelever (9) at pin (10) and causes the valve stem(11) to move the valve disc to close the inletorifice.

With the inlet orifice closed, gas is pulled fromthe lever side of chamber through the outlet(6). This gives a reduction of pressure in thechamber (8). As a result the pressurebecomes less than pressure in the spring sidechamber. Force of spring and air pressure inthe chamber on the spring side moves thediaphragm toward the lever. This turns(pivots) the lever and opens the valve disc,permitting additional gas flow to thecarburetor.

When the pressure on either side of thediaphragm is the same, the regulator sendsgas to the carburetor at a set amount.

CarburetorAir goes into the carburetor through air horn(2) and fills outer chamber (3). See Figures15-18. Air goes into inner chamber (9) (mixingchamber) by moving diaphragm (11) awayfrom ring (10). There are two diaphragms inthe carburetor. Fuel goes into the carburetorthrough fuel inlet (12), and goes by the loadadjusting valve (7) to the center of thecarburetor and into tube (5) for the fuel outlet.Fuel valve (4) is fastened to the diaphragm.With the diaphragm moved away from thering, fuel goes through the fuel valve and intothe inner chamber. The fuel and air mixture inthe inner chamber, goes down by the throttleplate (13) (not found on G3406) and into theinlet manifold.

With the engine stopped, spring (6) holds thediaphragm against the ring and holds the fuelvalve closed. No air or fuel can go to the innerchamber. As the engine is started, the vacuumin the cylinders, caused by the intake strokesof the pistons, causes a low pressure conditionin the inner chamber. This low pressure is feltby chamber (8), behind the diaphragmthrough small holes. This permits thepressure in the chamber to balance with thelow pressure condition in the inner chamber.As soon as the inlet pressure on thediaphragm is higher than the spring force, thediaphragm moves out. This also moves thefuel valve out and permits air and fuel to gointo the inner chamber.

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Figure 15: Carburetor Operation (G3406)(2) Air horn. (3) Outer chamber. (4) Fuel valve. (5) Fueloutlet tube. (6) Spring. (8) Chamber. (9) Inner chamber.(10) Ring. (11) Diaphragm.

Figure 16: Carburetor Operation (G3406)(7) Load adjusting valve. (12) Fuel inlet. (14) Idle screw.

Figure 17: Carburetor Operation (G3408 & G3412)(1) Balance line connection. (2) Air horn. (3) Outerchamber. (4) Fuel valve. (5) Fuel outlet tube. (6) Spring.(7) Load adjusting valve. (8) Chamber. (9) Innerchamber. (10) Ring. (11) Diaphragm. (12) Fuel inlet.(13) Throttle plate.

Figure 18: Carburetor Operation (View A-A) (G3408 &G3412)(1) Balance line connection. (2) Air horn. (7) Loadadjusting valve. (12) Fuel inlet.

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2301A Electric GovernorThe 2301A Electric Governor Control Systemconsists of the components that follow: 2301AElectric Governor Control (EGC), Actuator,Magnetic Pickup.

Figure 19: 2301A Electric Governor Control (EGC)

The 2301A Electric Governor System givesprecision engine speed control. The 2301Acontrol (Figure 19) measures engine speedconstantly and makes necessary correctionsto the engine fuel setting through an actuatorconnected to the fuel system.

The engine speed is felt by a magnetic pickup(Figure 20). The magnetic pickup is a singlepole, permanent magnet generator made ofwire coils (2) around a permanent magnetpole piece (4). See Figure 21. As the teeth ofthe flywheel ring gear (5) cut through themagnetic lines of force (1) around the pickup,an AC voltage is generated. The frequency ofthis voltage is directly proportional to enginespeed.

Figure 20: Magnetic Pickup Location(1) Magnetic pickup. (2) Flywheel housing.

This engine speed frequency signal (AC) issent to the 2301A Control Box where aconversion is made to DC voltage. The DCsignal is now sent on to control the actuator,and this voltage is inversely proportional toengine speed. This means that if engine speedincreases, the voltage output to the actuatordecreases. When engine speed decreases, thevoltage output to the actuator increases.

Figure 21: Schematic Of Magnetic Pickup(1) Magnetic lines of force. (2) Wire coils. (3) Gap. (4) Pole piece. (5) Flywheel ring gear.

The actuator (Figure 22) changes theelectrical input from the 2301A Control to amechanical output that is connected to the fuelsystem by linkage. For example, if the enginespeed is more than the speed setting, the2301A Control will decrease its output and theactuator will now move the linkage todecrease the fuel to the engine.

Figure 22: EG3P Actuator(3) Actuator. (4) Actuator lever.

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Woodward PSG GovernorsThe Woodward PSG (Pressure compensatedSimple Governor; Figure 23) can operate as anisochronous or a speed droop type governor.It uses engine lubrication oil, increased to apressure of 1200 kPa (175 psi) by a gear typepump inside the governor, to givehydra/mechanical speed control.

The governor is driven by the governor driveunit. This unit turns pilot valve bushing (13)clockwise as seen from the drive unit end ofthe governor (Figure 24). The pilot valvebushing is connected to a spring drivenballhead. Flyweights (7) are fastened to theballhead by pivot pins. The centrifugal forcecaused by the rotation of the pilot valvebushing causes the flyweights to pivot out.This action of the flyweights changes thecentrifugal force to axial force against speederspring (5). There is a thrust bearing (9)between the toes of the flyweights and theseat for the speeder spring. Pilot valve (12) isfastened to the seat for the speeder spring.Movement of the pilot valve is controlled bythe action of the flyweights against the force ofthe speeder spring.

The engine is at the governed (desired) rpmwhen the axial force of the flyweights is thesame as the force of compression in thespeeder spring. The flyweights will be in theposition shown. Control ports (14) will beclosed by the pilot valve.

When the force of compression in the speederspring increases (operator increases desiredrpm) or the axial force of the flyweightsdecreases (load on the engine increases) thepilot valve will move in the direction of thedrive unit. This opens control ports (14).Pressure oil flows through a passage in thebase to chamber (B). The increased pressurein chamber (B) causes power piston (6) tomove. The power piston pushes strutassembly (4), that is connected to output shaftlever (3). The action of the output shaft levercauses counterclockwise rotation of outputshaft (2). This moves carburetor controllinkage (15) in the THROTTLE OPENEDdirection (Figure 23).

Figure 23: PSG Governor Installed(2) Output Shaft. (15) Carburetor control linkage.

As the power piston moves in the direction ofreturn spring (1) the volume of chamber (A)increases. The pressure in chamber (A)decreases. This pulls the oil from the chamberinside the power piston, above buffer piston(11) into chamber (A). As the oil moves outfrom above the buffer piston to fill chamber(A) the buffer piston moves up in the bore ofthe power piston. Chambers (A and B) areconnected respectively to the chambers aboveand below the pilot valve compensating land(10). The pressure difference felt by the pilotvalve compensating land adds to the axialforce of the flyweights to move the pilot valveup and close the control ports. When the flowof pressure oil to chamber (B) stops so doesthe movement of the fuel control linkage.

When the force of compression in the speederspring decreases (operator decreases desiredrpm) or the axial force of the flyweightsincreases (load on the engine decreases) thepilot valve will move in the direction of thespeeder spring. This opens the control ports.Oil from chamber (B) and pressure oil fromthe pump will dump through the end of thepilot valve bushing. The decreased pressure inchamber (B) will let the power piston move inthe direction of the drive unit. The returnspring pushes against the strut assembly. Thismoves the output shaft lever. The action of theoutput shaft lever causes clockwise rotation ofthe output shaft. This moves the carburetorcontrol linkage in the THROTTLE CLOSEDdirection (Figure 23).

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Figure 24: Schematic Of PSG Governor(1) Return spring. (2) Output shaft. (3) Output shaft lever. (4) Strut assembly. (5) Speeder spring. (6) Power piston. (7) Flyweights. (8) Needle valve. (9) Thrust bearing. (10) Pilot valve compensating land. (11) Buffer piston. (12) Pilot valve. (13) Pilot valve bushing. (14) Control ports. (A) Chamber. (B) Chamber.

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On PSG governors not equipped with electricspeed adjustment, (Figure 25) speed can beadjusted with screw (1). When the screw isturned clockwise it pushes the link assembly(2) against speeder spring (3). This causes anincrease in the force of speeder spring andpilot valve (4) will move toward governordrive unit. The engine will increase speed untilit gets to the desired rpm. When the screw isturned counterclockwise the link assemblymoves away from speeder spring. This causesa decrease in the force of the speeder springand the pilot valve will move away fromgovernor drive unit. The engine will decreasespeed until it gets to the desired rpm.

Figure 25: Non-electric PSG Governor (1) Screw. (2) Link assembly. (3) Speeder spring. (4) Pilot valve.

Engines with non-electric governors are alsoequipped with a governor control group(Figure 26) to allow easier speed adjustment.

Figure 26: Governor Control Group(5) Positive lock lever. (6) Link assembly lever. (7) Governor

As lever (5) is moved toward governor (7),linkage causes lever (6) to move in the samedirection. The link assembly lever is clampedto the shaft of link assembly (2). As the shaftrotates, the link assembly pushes againstspeeder spring (3). This causes pilot valve (4)to move toward the governor drive unit. Theengine will increase speed until it gets todesired rpm.

When lever (5) is moved away from thegovernor, the link assembly lever moves in thesame direction. This causes the link assemblyto move away from the speeder spring. Thepilot valve then moves away from thegovernor drive unit and engine speeddecreases until desired rpm is reached.

Figure 27: PSG Electric-Type Governor(8) Synchronizing motor. (9) Clutch assembly. (10) Link assembly. (11) Speeder spring. (12) Pilot valve.

On electric type PSG governors (Figure 27),speed adjustments are made by a 24V DCreversible synchronizing motor (8). Themotor is controlled by a switch that can be putin a remote location.

The synchronizing motor drives clutchassembly (9). The clutch assembly protectsthe motor if it is run against the adjustmentstops.

When the clutch assembly is turned clockwiseit pushes link assembly (10) against speederspring (11). The force of compression in thespeeder spring is increased. This causes pilotvalve (12) to move toward the governor driveunit. The engine will increase speed, then getstability at a new desired rpm.

When the clutch assembly is turnedcounterclockwise the link assembly movesaway from the speeder spring. The force ofcompression in the speeder spring isdecreased. This causes the pilot valve to moveaway from the governor drive unit. The enginewill decrease speed, then get stability at a newdesired rpm.

Note: The clutch assembly can be turnedmanually if necessary.

Speed droop is the difference between no loadrpm and full load rpm. This difference in rpmdivided by the full load rpm and multiplied by100 is the percent of speed droop.

No load speed – Full load speed 3 100

Full load speed

5 % of speed droop

Figure 28: PSG Governor (View A-A from Figure 31)(10) Link assembly. (13) Pivot pin. (14) Output shafts.(15) Droop adjusting bracket. (16) Shaft assembly.

The speed droop of the PSG governor can beadjusted. The governor is isochronous when itis adjusted so that the no load and full loadrpm is the same. Speed droop permits loaddivision between two or more engines thatdrive generators connected in parallel orgenerators connected to a single shaft.

Speed droop adjustment on PSG governors(Figure 28) is made by movement of pivot pin(13). When the pivot pin is put in alignmentwith output shafts (14), movement of theoutput shaft lever will not change the force ofthe speeder spring. When the force of thespeeder spring is kept constant, the desiredrpm will be kept constant. When the pivot pinis moved out of alignment with the outputshafts, movement of the output shaft lever willchange the force of the speeder springproportional to the load on the engine. Whenthe force of the speeder spring is changed, thedesired rpm of the engine will change.

An adjustment bracket (15) outside thegovernor connected to the pivot pin by thelink assembly and shaft assembly (16) is usedto adjust speed droop.

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Air Inlet and Exhaust Systems

Exhaust Bypass Group(Engines With Turbocharger)

Figure 29: Exhaust Bypass System(1) Air inlet pipe. (2) Turbocharger. (3) Exhaustmanifold housing. (4) Differential pressure regulator. (5) Regulator control line.

Figure 30: Exhaust Bypass Group(6) Regulator control line connection. (7) Diaphragm. (8) Spring. (9) Bypass valve. (10) Breather location.

The exhaust bypass group (Figure 30) isinstalled on the exhaust manifold housing (3).See Figure 29. It controls the amount ofexhaust gases to the turbine wheel. Theexhaust bypass valve (9) is activated directlyby a pressure differential between the airpressure (atmosphere) and turbochargercompressor outlet pressure to the carburetor.

One side of the diaphragm (7) in the regulator(4) feels atmospheric pressure through abreather (10) in the top of the regulator. Theother side of the diaphragm feels air pressurefrom the outlet side of the turbocharger

compressor through a control line (5)connected at (6). When outlet pressure to thecarburetor gets to the correct value, the forceof the air pressure on the diaphragm movesthe diaphragm which overcomes the force ofthe spring (8) and atmospheric pressure. Thisopens the valve, and stops exhaust gases fromgoing to the turbine wheel.

The location of the bypass passage is insidethe exhaust manifold housing. Under constantload conditions, the valve will take a setposition, permitting just enough exhaust gasto go to the turbine wheel to give the correctair pressure to the carburetor.

Balance LineThe balance line controls the correctdifferential pressure between the linepressure regulator and carburetor inlet.

When the load on the engine changes, boostpressure from the turbocharger changes inthe inlet manifold. The balance line sends asignal of this change in pressure to the springside of the diaphragm in the line pressureregulator. This pressure change causes theregulator diaphragm to move the lineregulator valve to correct the gas pressure tothe carburetor. By this method, the correctdifferential pressure between the regulator forthe line pressure and carburetor inlet iscontrolled.

Valve System ComponentsThe valve system components (Figure 31)control the flow of inlet air and exhaust gasesinto and out of the cylinders during engineoperation.

The crankshaft gear drives the camshaft gear.The camshaft gear must be timed to thecrankshaft gear to get the correct relationbetween piston and valve movement.

The camshaft has two cams for each cylinder.One cam controls the exhaust valves, theother controls the intake valves.

22

23

Figure 31: Valve System Components(1) Intake bridge. (2) Intake rocker arm. (3) Push rod.(4) Rotocoil. (5) Valve spring. (6) Valve guide. (7) Intake valves. (8) Lifter. (9) Camshaft.

As the camshaft turns, the lobes of camshaft(9) cause lifters (8) to go up and down. Thismovement makes push rods (3) move rockerarms (2). Movement of the rocker armsmakes bridge (1) move up and down ondowels mounted in the cylinder head. Thebridges let one rocker arm open and close twovalves (intake or exhaust). There are twointake and two exhaust valves for eachcylinder.

Rotocoils (4) cause the valves to turn whilethe engine is running. The rotation of thevalves keeps the deposit of carbon on thevalves to a minimum and gives the valveslonger service life.

Valve springs (5) cause the valves to closewhen the lifters move down.

AftercoolerThe aftercooler is installed on the top of theinlet manifold. Water flow through theaftercooler, lowers the temperature of the inletair from the turbocharger. With cooler air, anincrease in weight of air will permit more fuel

to burn. This gives an increase in power. Theaftercooler can be changed to use sea water asthe coolant.

Figure 32: Cross Section Of Turbocharger(1) Air inlet. (2) Compressor wheel. (3) Compressoroutlet. (4) Lubrication inlet port. (5) Turbine wheel.(6) Thrust bearing. (7) Shaft bearings. (8) Exhaustoutlet.

TurbochargerThe turbochargers (Figure 32) are installed atthe rear of the exhaust manifolds. All theexhaust gases from the engine go through theturbocharger.

The exhaust gases go through the blades ofturbine wheel (4). This causes the turbinewheel and compressor wheel (2) to turn.

Clean inlet air from the air cleaners is pulledthrough air inlet (1) of the compressorhousing by the compressor wheel. Thecompressor wheel causes a compression ofthe air. The air goes to the inlet manifold ofthe engine.

The turbocharger bearings use engine oilunder pressure for lubrication. The oil comesin through port (3) and goes throughpassages for lubrication of the thrust bearing(5), the rings and shaft bearings (6). Oil fromthe turbocharger goes through an opening inthe bottom of the center section and to theengine sump.

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Lubrication System

Oil Flow Through The Oil CoolerAnd Oil Filters

Figure 33: Schematic Of Oil Flow(1) To oil manifold. (2) Filter bypass valve. (3) Engine oil cooler. (4) Cooler bypass valve. (5) Oil pump. (6) Oil pan. (7) Oil filters.

Figure 34: Lubrication System Components (2) Filter bypass valve. (3) Engine oil cooler. (6) Oil pan.(7) Oil filters.

With the engine warm (normal operation), oilis pulled from oil pan (6) through a bellassembly and pipe to oil pump (5). SeeFigures 33 and 34. The oil pump sends oilthrough a pipe to a passage in the cylinderblock. The oil then goes through oil coolerbypass valve (4) into oil cooler (3). The oilgoes out of the oil cooler through oil filters(7). The clean oil then goes through oil filterbypass valve (2), then into the oil manifold onthe right side of the cylinder block.

When the engine is cold (starting condition),bypass valves (2 and 4) open because cold oilwith high viscosity causes a restriction to theoil flow through oil cooler (3) and the filters.When the bypass valves are open, oil flows

directly through passages in the valve body tothe oil manifold.

When the oil gets warm, the pressuredifference at the bypass valves decreases andthe bypass valves close. This gives normal oilflow through the oil cooler and oil filters.

The bypass valves will also open when there isa restriction in the oil cooler or oil filters. Thisaction does not let an oil cooler or oil filterwith a restriction prevent the lubrication of theengine.

There is also a bypass valve in the engine oilpump. This bypass valve controls the pressureof the oil from the oil pump. The oil pump canput more oil into the system than is needed.When there is more oil than needed, the oilpressure goes up and the bypass valve willopen. This lets the oil that is not needed to goback to the inlet oil passage of the oil pump.

From oil manifold (16), oil is sent throughdrilled passages in the cylinder block thatconnect main bearings (15) and camshaftbearings (13). See Figure 35. Oil goes throughdrilled holes in the crankshaft to givelubrication to the connecting rod bearings. Asmall amount of oil is sent through oil jettubes (14) to make the pistons cooler. Oil goesthrough grooves in the bores for the front andrear camshaft bearings and then into oilpassages (3) that connects the valve lifterbores (4). These passages give oil underpressure for the lubrication of the valve lifters.

Oil is sent from the lifter bores throughpassage (11) to an oil passage in bracket (5)(next to cylinder No. 4) to supply pressurelubrication to rear rocker arm shaft (2). Oil isalso sent from front main bearing borethrough passage (9) to an oil passage in frontbracket (7) for front rocker arm shaft (6).

Holes in the rocker arm shafts lets the oil givelubrication to the valve system components inthe cylinder head.

The idler gear gets oil from passage (10) inthe cylinder block through a passage in theidler gear shaft installed on the front of thecylinder block.

There is a pressure control valve in the oilpump. This valve controls the pressure of theoil coming from the oil pump. The oil pumpcan put more oil into the system than isneeded. When there is more oil than needed,the oil pressure goes up and the valve willopen. This allows the oil that is not needed togo back to the inlet oil passage of the oilpump.

After the lubricating oil has done its work, itgoes back to the engine oil pan.

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Oil Flow In The Engine (G3406)

Figure 35: Engine Oil Flow Schematic(1) Bracket for rocker arm shaft. (2) Rocker arm shaft. (3) Oil passage to lifters. (4) Valve lifter bore. (5) Oil supply rocker shaft bracket. (6) Rocker arm shaft. (7) Oil supply rocker shaft bracket. (8) Oil passage toaccessory drive. (9) Oil passage to rocker shaft bracket and accessory drive. (10) Oil passage to idler gear shaft. (11) Oil passage to rocker shaft bracket. (12) Oil passage. (13) Camshaft bearing. (14) Oil jet tubes. (15) Main bearing.(16) Oil manifold. (17) Oil passage from the oil pump to the oil cooler and filter. (18) Oil passage from the oil cooler andfilter.

The oil manifolds are cast into the sides of thecylinder block. Oil goes into manifold (16)from the bypass valve body. See Figures 36and 37. From manifold (16) oil is sent tomanifold (12) through drilled passages in thecylinder block that connect main bearingbores (17) and camshaft bearing bores (9). Oilgoes through holes in the bearings and givesthem lubrication. Oil from the main bearingsgoes through holes drilled in the crankshaft togive lubrication to the connecting rodbearings. A small amount of oil from the oilmanifolds goes through tubes (10) to makethe pistons cooler.

Oil goes through grooves in the outside of thefront and rear camshaft bearings to passages(7 and 8). The oil in these passages giveslubrication to the valve lifters and rocker armshafts. Holes in the rocker arm shafts let the

oil give lubrication to the valve systemcomponents in the cylinder head.

The magneto and governor drive housing andgovernor get oil from passage (5) in thecylinder block. Oil for the hydraulic operationof the hydra/mechanical governor comesfrom a small gear pump inside the governor.

The bearing of the idler gear on the front ofthe engine gets oil through a passage in theidler gear shaft that is connected to passage(14).

The bearing for the balancer gear at the rearof the engine (G3408 only) gets oil through apassage in the balancer gear shaft that isconnected to passage (2).

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Figure 36: Schematic Of Oil Flow In The G3408 Engine(1) Passage is plugged. (2) Oil passage line. (3) To rocker arm shaft. (4) To turbocharger. (5) To magneto and governordrive housing. (6) Rocker arm shaft. (7) To rocker arm shaft and valve lifters. (8) To valve lifters. (9) Bore for camshaftbearings. (10) Piston cooling jets. (11) to SCAC water pump. (12) Oil manifold (left side). (13) To timing gear housing. (14) To front idler gear. (15) Oil supply line to manifold in cylinder block. (16) Oil manifold (right side). (17) Main bearing bores.

Oil Flow In The Engine (G3408 and G3412)

Tube assembly (18) gives oil to the turbochargerimpeller shaft bearings. (Figures 38 and 39). Theoil goes out of the turbocharger through tubeassembly (19) to the flywheel housing.

Oil that gives pressure lubrication to gear shaftsand bearings then flows free to give lubricationto the gear teeth. After the oil for lubrication hasdone its work it flows free back to the oil pan.

Figure 38: Turbocharger Lubrication (G3408 Shown)(18) Oil supply line to turbocharger. (19) Oil drain linefrom turbocharger.

Figure 39: Turbocharger Lubrication (G3412 Shown)(18) Oil supply line to turbocharger. (19) Oil drain linefrom turbocharger.

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Figure 37: Schematic Of Oil Flow In The G3412 Engine(1) Passage is plugged. (3) To rocker arm shaft. (4) To turbocharger. (5) To magneto and governor drive housing. (6) Rockerarm shaft. (7) To rocker arm shaft and valve lifters. (8) To valve lifters. (9) Bore for camshaft bearings. (10) Piston cooling jets.(11) to SCAC water pump. (12) Oil manifold (left side). (13) To timing gear housing. (14) To front idler gear. (15) Oil supplyline to manifold in cylinder block. (16) Oil manifold (right side). (17) Main bearing bores.

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Cooling System

Jacketwater System (G3406)This engine has a pressure type cooling system(Figure 40) equipped with a shunt line (5).

A pressure type cooling system gives twoadvantages. The first advantage is that thecooling system can have safe operation at atemperature that is higher than the normalboiling (steam ) point of water. The secondadvantage is that this type system preventscavitation (the sudden making of low pressurebubbles in liquids by mechanical forces) in thewater pump. With this type system, it is moredifficult for an air or steam pocket to be madein the cooling system.

Figure 40: Cooling System (Engine Warm)(1) Cylinder head. (2) Water temperature regulator. (3) Outlet hose. (4) Vent tube. (5) Shunt line. (6) Water elbow. (7) Water pump. (8) Cylinder block. (9) Oil cooler. (10) Inlet hose. (11) Radiator.

In operation, water pump (7) sends most ofthe coolant from radiator (11) or heatexchanger (not shown here) to oil cooler (9).

The coolant from oil cooler goes through abonnet and elbow into the cylinder block (8).Inside the cylinder block, the coolant goesaround the cylinder liners and up through thewater directors into the cylinder head. Thewater directors send the flow of coolantaround the valves and the passages forexhaust gases in the cylinder head. Thecoolant then goes to the front of the cylinderhead. At this point, water temperatureregulator (2) controls the direction of coolantflow.

If the coolant temperature is less than normalfor engine operation, the water temperatureregulator is closed. The coolant flows throughthe regulator housing and elbow (6) back tothe water pump.

If the coolant is at normal operatingtemperature (engine warm), the watertemperature regulator is open and the coolantflows to the radiator or heat exchangerthrough outlet hose (3). The coolant is madecooler as it moves through the radiator. Whenthe coolant gets to the bottom of the radiator,it goes through inlet hose (10) and into thewater pump.

Note: The water temperature regulator is animportant part of the cooling system. Itdivides coolant flow between radiator or heatexchanger and bypass (water elbow) asnecessary to maintain the correcttemperature. If the water temperatureregulator is not installed in the system, thereis no mechanical control, and most of thecoolant will take the path of least resistancethrough the bypass. This will cause the engineto overheat in hot weather. In cold weather,even the small amount of coolant that goesthrough the radiator is too much, and theengine will not get to normal operatingtemperatures.

Shunt line (5) gives several advantages to thecooling system.

1. The shunt line gives a positive pressure atthe water pump inlet to prevent pumpcavitation.

2. A small flow of coolant constantly goesthrough the shunt line to the inlet of the waterpump. This causes a small amount of coolantto move constantly through vent tube (4)between the lower and upper compartment inthe radiator top tank. Since the flow throughthe vent tube is small the volume of the uppercompartment is large, air in the coolant comesout of the coolant as it goes into the uppercompartment.

3. The shunt line is a fill line when the coolingsystem is first filled with coolant. This lets thecooling system fill from the bottom to pushany air in the system out the top.

Jacketwater System (G3408 &G3412)This engine has a pressure type coolingsystem. A pressure type cooling system givestwo advantages. The first advantage is that thecooling system can have safe operation at atemperature that is higher than the normalboiling (steam) point of water. The secondadvantage is that this type system preventscavitation (the sudden making of low pressurebubbles in liquids by mechanical forces) in thewater pump. With this type system, it is moredifficult for an air or steam pocket to be madein the cooling system.

This engine can be cooled by a radiator orheat exchanger. The following explanation andFigure 41 covers only the cooling circulationof the engine.

In normal operation (engine warm), waterpump (2) receives coolant through the inletconnection (1) and sends the coolant toengine oil cooler (13) and the oil coolerbypass (12). The oil cooler outlet sends thecoolant from the cooler and bypass to thewater cooled turbocharger (7) and to theengine cylinder block. Coolant to theturbocharger flows through line (6) throughthe turbocharger and returns to the watercooled exhaust manifold (11) and on to the

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Figure 41: Cooling System Schematic (G3408 Shown)(1) Water inlet connection. (2) Water pump. (3) Bypass lines. (4) Temperature regulator housings. (5) Water outlet connections. (6) water to turbocharger. (7) Water cooled turbocharger. (8) Water from turbocharger.(9) Aftercooler. (10) Separate circuit water pump. (11) Water cooled exhaust manifold. (12) Oil cooler bypass. (13) Engine oil cooler.

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block. The coolant to the cylinder blockcirculates through the block up through thecylinder heads, on to the water temperatureregulator housings (4). Part of the coolant inthe housing flows into the water cooled exhaustmanifolds, and part of the coolant passesthrough open temperature regulators throughoutlet connections (5) to be cooled. The coolantin the exhaust manifold flows into the cylinderblock through the head and back to thehousing. The water pump will pump the cooledcoolant through the engine to keep the cyclegoing.

Note: The water temperature regulator is animportant part of the cooling system. It dividescoolant flow between the radiator and thebypass lines (3) as necessary to maintain thecorrect temperature. If the water temperatureregulator is not installed in the system, there isno mechanical control, and most of the coolantwill take the path of least resistance throughthe bypass. This will cause the engine tooverheat in hot weather. In cold weather, eventhe small amount of coolant that goes throughthe radiator or heat exchanger is too much, andthe engine will not get to normal operationtemperatures.

When the engine is cold, the water temperatureregulators are closed. The coolant in thetemperature regulator housings flows throughthe bypass lines to the water pump. The coolantcontinues to flow through system as describedabove except the coolant does not flow out tobe cooled.

Total system coolant capacity will depend onthe size of the radiator or heat exchanger. Usethe correct amount of permanent antifreezeand pure water to provide freeze protection tothe lowest expected outside temperature. Add aconcentration of three to six percent corrosioninhibitor.

Separate Circuit Aftercooler (SCAC)SystemThe aftercooler (9) is cooled by a separatewater circuit. The separate water circuit is usedto maintain a specific and constant watertemperature. Water is pumped from theseparate water supply by pump (10) throughthe aftercooler and back to the water supply.This system is also used on the G3406.

Basic Block

Cylinder Block, Liners AndHeadsThe block is a one-piece design and cast ofhigh tensile strength iron in the enginemanufacturer’s own foundry. Cylinder wearsurfaces are induction hardened over theirentire length. Pistons are a lightweightaluminum alloy which is elliptically groundacross the skirt and tapered from crown toskirt.

The G3406 cylinder block has six cylindersarranged inline. The thrust bearings areinstalled on the middle main bearing journaland control the end play of the crankshaft.

The cylinders in the left side of the G3408 andG3412 block make an angle of 65 degrees withthe cylinders in the right side of the block.The main bearing caps are fastened to theblock with two bolts per cap.

The cylinder liners can be removed forreplacement. The top surface of the block isthe seat for the cylinder liner flange. Enginecoolant flows around the liners to keep themcool. Three O-ring seals around the bottom ofthe liner make a seal between the liner andthe block. A filler band at the top of each linerforms a seal between the liner and thecylinder block.

A steel spacer plate is used between thecylinder head and block. A thin gasket is usedbetween the plate and the block to seal waterand oil. A thick gasket of metal and non-metallic fiber is used between the plate andthe head to seal combustion gases, water andoil.

The engine has a single, cast head on eachside. Four vertical valves (two intake and twoexhaust), controlled by a pushrod valvesystem, are used per each cylinder. Theopening for the spark plug adapter is locatedbetween the four valves. Series ports(passages) are used for both intake andexhaust valves.

The size of the pushrod openings through thehead permits the removal of the valve lifterswith the head installed.

Valve guides without shoulders are pressedinto the cylinder head.

Pistons, Rings And ConnectingRodsThe piston on the G3408 has three rings; twocompression rings (top and intermediate) andone oil ring. The G3406 and G3412 have anadditional compression ring. All the rings arelocated above the piston pin bore. Thecompression ring seats in an iron band whichis cast in the piston. The oil ring is springloaded. External cast notches in the oil ringgroove return oil to the crankcase.

The full-floating piston pin is held in place bytwo snap rings which fit in grooves in the pinbore.

The connecting rod has a taper on the pinbore end. This gives the rod and piston morestrength in the areas with the most load.

Oil spray jets, located on the cylinder blockmain webs, direct oil to cool and givelubrication to the piston components andcylinder walls.

Gallery cooled pistons have two cooling jets,per cylinder. One cools the under crown of thepiston and the other directs oil into a castgallery behind the piston rings.

CrankshaftThe crankshaft changes the combustionforces in the cylinder into usable rotatingtorque which powers the machine. Vibration,caused by combustion impacts along thecrankshaft, is kept small by a vibration damperon the front of the crankshaft.

There is a gear at the front of the crankshaft todrive the timing gears and the oil pump. Lipseals and wear sleeves are used at both endsof the crankshaft for easy replacement and areduction of maintenance cost. Pressure oil issupplied to all bearing surfaces throughdrilled holes in the crankshaft. The crankshaft

is supported by five main bearings in theG3408 engines and by seven main bearings inthe G3406 and G3412 engines. A thrust plateat either side of the center main bearingcontrols the endplay of the crankshaft for theG3408 and G3412.

CamshaftThe engine has a single camshaft that isdriven at the front end. Five bearings for theG3408 and seven bearings for the G3406 andG3412 support the camshaft. As the camshaftturns, each cam (lobe) (through the action ofvalve system components) moves either twoexhaust valves or two intake valves for eachcylinder. The camshaft gear must be timed tothe crankshaft gear. The relation of the cams(lobes) to the camshaft gear cause the valvesin each cylinder to open and close at thecorrect time.

A gear on the rear of the camshaft is used todrive the balancer gear on G3408 engines.

Vibration DamperThe twisting of the crankshaft, due to theregular power impacts along its length, iscalled twisting (torsional) vibration. The fluidtype vibration damper is installed on the frontend of the crankshaft. It is used for reductionof torsional vibrations and stops the vibrationfrom building up to amounts that causedamage.

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Electrical System

Engine Electrical SystemThe electrical system can have three separatecircuits: the charging circuit, the startingcircuit and the low amperage circuit. Some ofthe electrical system components are used inmore than one circuit. The battery (batteries),circuit breaker, ammeter, cables and wiresfrom the battery are all common in each of thecircuits.

Note: Other electrical systems andcomponents are covered in the Attachmentssection of the Service Manual.

The charging circuit is in operation when theengine is running. An alternator makeselectricity for the charging circuit. A voltageregulator in the circuit controls the electricaloutput to keep the battery at full charge.

NOTICEThe disconnect switch, if so equipped, mustbe in the ON position to let the electricalsystem function. There will be damage tosome of the charging circuit components if theengine is running with the disconnect switchin the OFF position.

If the engine has a disconnect switch, thestarting circuit can operate only after thedisconnect switch is put in the ON position.

The starting circuit is in operation only whenthe start switch is activated.

The charging circuit and the low amperagecircuit are both connected through theammeter. The starting circuit is not connectedthrough the ammeter.

Charging System Components

Alternator (Delco-Remy)

Figure 42: 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 (Figure 42) is driven by V-beltsfrom the crankshaft pulley. This alternator is athree phase, self-rectifying charging unit, andthe regulator (1) is part of the alternator.

This alternator design has no need for sliprings or brushes, and the only part that hasmovement is the rotor assembly (7). Allconductors that carry current are stationary.The conductors are: the field winding (6),stator windings (3), six rectifying diodes andthe regulator circuit components.

The rotor assembly has many magnetic poleslike fingers with air space between eachopposite pole. The poles have residualmagnetism (like permanent magnets) thatproduce a small amount of magnet-like lines offorce (magnetic field) between the poles. Asthe rotor assembly begins to turn between thefield winding and the stator windings, a smallamount of alternating current (AC) isproduced in the stator windings from thesmall magnetic lines of force made by theresidual magnetism of the poles. This ACcurrent is changed to direct current (DC)when it passes through the diodes of therectifier bridge (5). Most of this current goesto charge the battery and to supply the lowamperage circuit, and the remainder is sent onto the field windings. The DC current flow

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through the field windings (wires around aniron core) now increases the strength of themagnetic lines of force. These stronger linesof force now increase the amount of ACcurrent produced in the stator windings. Theincreased speed of the rotor assembly alsoincreases the current and voltage output ofthe alternator.

The voltage regulator is a solid state(transistor, stationary parts) electronic switch.It feels the voltage in the system and switcheson and off many times a second to control thefield current (DC current to the fieldwindings) for the alternator to make theneeded voltage output.

Grounding PracticesProper grounding for vehicle and engineelectrical systems is necessary for propermachine performance and reliability.Improper grounding will result inuncontrolled and unreliable electrical circuitpaths which can result in damage to mainbearings and crankshaft journal surfaces.Uncontrolled electrical circuit paths can alsocause electrical noise which may degradevehicle and radio performance.

To insure proper functioning of the vehicleand engine electrical systems, and engine-to-frame ground strap with a direct path to thebattery must be use. This may be provided byway of a starting motor, a frame to startingmotor ground, or a direct frame to engineground.

Ground wires/straps should be combined atground studs dedicated for ground use only.The engine alternator must be battery (–)grounded with a wire size adequate to handlefull alternator charging current.

NOTICEThis engine may be equipped with a 24 voltstarting system. Use only equal voltage forboost starting. The use of a welder or highervoltage will damage the electrical system.

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Starting Systems

There are two types of starting systemsavailable for Caterpillar Engines — air andelectric.

The choice of systems depends on availabilityof the energy source. Availability of space forenergy of storage and ease of recharging theenergy banks are considerations fordetermining the type of starting system to beused.

ElectricElectric starting (Figure 43) is the mostconvenient to use. It is least expensive and ismost adaptable for remote control andautomation.

BatteriesBatteries provide sufficient power to crankengines long and fast enough to start. Lead-acid types are common, have high outputcapabilities, and lowest first cost. Nickel-cadmium batteries are costly, but have longshelf life and require minimum maintenance.Nickel-cadmium types are designed for longlife and may incorporate thick plates whichdecrease high discharge capability. Consultthe battery supplier for specificrecommendations.

Two considerations in selecting properbattery capacity are:

• The lowest temperature at which the enginemight be cranked.

• The parasitic load imposed on the engine. Agood rule of thumb is to select a batterypackage which will provide at least four 30second cranking periods (total of 2 minutescranking). An engine should not be crankedcontinuously for more than 30 seconds orstarter motors may overheat.

Ambient temperatures drastically affectbattery performance and chargingefficiencies. Maintain 32°C (90°F) maximumtemperature to assure rated output. Impact ofcolder temperatures is described in Figure 44.

Figure 43: Electric Starting System.

Figure 44: Impact Of Cold Temperatures.

Locate cranking batteries for easy visualinspection and maintenance. They must beaway from flame or spark sources and isolatedfrom vibration. Mount level on nonconductingmaterial and protect from splash and dirt. Useshort slack cable lengths and minimizevoltage drops by positioning batteries near thestarting motor.

Disconnect the battery charger whenremoving or connecting battery leads. Solid-state equipment, i.e., electronic governor,speed switches, can be harmed if subjected tocharger’s full output.

Battery ChargerVarious chargers are available to replenish abattery. Trickle chargers are designed forcontinuous service on unloaded batteries.They automatically shut down to milliamperecurrent when batteries are fully charged.

Overcharging shortens battery life and isrecognized by excessive water loss.Conventional lead-acid batteries require lessthan 59.2 mL (2 oz.) make-up water during30 hours of operation.

°F °C

Temperature vs. Output

27°C (80°F)Ampere Hours Output Rating

80

32

0

28

0

-18

100

65

40

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Float-equalize chargers are more expensivethan trickle chargers and are used inapplications demanding maximum battery life.These chargers include line and loadregulation, and current limiting devices,which permit continuous loads at rated output.

Both trickle chargers and float equalizechargers require a source of A/C power whilethe engine is not running. Chargers must becapable of limiting peak currents duringcranking cycles or have a relay to disconnectduring cranking cycles. Where engine-drivenalternators and battery chargers are bothused, the disconnect relay usually disconnectsthe battery charger during engine crankingand running.

Engine-driven generators or alternators canbe used, but have the disadvantage ofcharging batteries only while the engine runs.Where generator sets are subject to manystarts, insufficient battery capacity couldthreaten dependability.

Solenoid

Figure 45: Solenoid Schematic(1) Electromagnet. (2) Hollow cylinder. (3) Plunger. (4) Shift lever.

A solenoid (Figure 45) is a magnetic switchthat does two basic operations:

a. Closes the high current starter motorcircuit with a low current start switchcircuit.

b. Engages the starter motor pinion with thering gear.

The solenoid switch is made of anelectromagnet (one or two sets of windings)(1) around a hollow cylinder (2). There is aplunger (core)(3) with a spring load inside thecylinder that can move forward and backward.When the start switch is closed and electricityis sent through the windings, a magnetic fieldis made that pulls the plunger forward in thecylinder. This moves the shift lever (4)(connected to the rear of the plunger) toengage the starter pinion drive gear with thering gear. The front end of the plunger thenmakes contact across the battery and motorterminals of the solenoid, and the startermotor begins to turn the flywheel of theengine.

When the start switch is opened, current nolonger flows through the windings. The springnow pushes the plunger back to the originalposition, and, at the same time, moves thepinion gear away from the flywheel.

When two sets of windings in the solenoid areused, they are called the hold-in winding andthe pull-in winding. Both have the samenumber of turns around the cylinder, but thepull-in winding uses a larger diameter wire toproduce a greater magnetic field. When thestart switch is closed, part of the current flowsfrom the battery through the hold-in windings,and the rest flows through the pull-in windingsto motor terminal, then through the motor toground. When the solenoid is fully activated(connection across battery and motor terminalis complete), current is shut off through thepull-in windings. Now only the smaller hold-inwindings are in operation for the extendedperiod of time it takes to start the engine. Thesolenoid will now take less current from thebattery, and heat made by the solenoid will bekept at an acceptable level.

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Starter Motor

Figure 46: Starter Motor Cross Section(1) Field. (2) Solenoid. (3) Clutch. (4) Pinion. (5)Commutator. (6) Brush assembly. (7) Armature.

The starter motor (Figure 46) is used to turnthe engine flywheel fast enough to get theengine running.

The starter motor has a solenoid (2). Whenthe start switch is activated, the solenoid willmove the starter pinion (4) to engage it withthe ring gear on the flywheel of the engine.The starter pinion will engage with the ringgear before the electric contacts in thesolenoid close the circuit between the batteryand the starter motor. When the circuitbetween the battery and the starter motor iscomplete, the pinion will turn the engineflywheel. A clutch (3) gives protection for thestarter motor so that the engine cannot turnthe starter motor too fast. When the startswitch is released, the starter pinion will moveaway from the ring gear.

Circuit Breaker

Figure 47: Circuit Breaker Schematic(1) Reset button. (2) Disc in open position. (3) Contacts.(4) Disc. (5) Battery circuit terminals.

The circuit breaker (Figure 47) is a switchthat opens the battery circuit (5) if the currentin the electrical system goes higher than therating of the circuit breaker.

A heat activated metal disc (4) with a contactpoint (3) completes the electric circuitthrough the circuit breaker. If the current inthe electrical system gets too high, it causesthe metal disc to get hot. This heat causes adistortion of metal disc which opens thecontacts (2) and breaks the circuit. A circuitbreaker that is open can be reset after it cools.Push the reset button (1) to close the contactsand reset the circuit breaker.

Magnetic Pickup

Figure 48: Magnetic Pickup(1) Clearance dimension. (2) Pole piece. (3) Wire coils.(4) Locknut. (5) Gear tooth.

The magnetic pickup (Figure 48) is a singlepole, permanent magnet generator made ofwire coils (3) around a permanent magnetpole piece (2). As the teeth of the flywheelring gear (5) go through the magnetic lines offorce around the pickup, an AC voltage ismade. A positive voltage is made when eachtooth goes by the pole piece. Each time thespace between the teeth goes by a pole piece,a negative voltage is made. Engine speed isthen determined by the frequency of thesesignals when the numbers of the teeth on theflywheel is known.

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Air StartThe air starting motor (Figures 49 and 50) isused to turn the engine flywheel fast enoughto get the engine running.

Figure 49: Air Starting System(1) Air start control valve. (2) Air starting motor. (3) Relay valve. (4) Oiler.

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

For engines which do not have heavy loadswhen starting, the regulator setting isapproximately 690 kPa (100 psi). This settinggives a good relationship between enoughcranking speeds for easy starting and thelength of time the air starting motor can turnthe engine flywheel before the air supply isgone.

If the engine has a heavy load which can notbe disconnected during starting, the setting ofthe air pressure regulating valve needs to behigher in order to get enough speed for easystarting.

The air consumption is directly related tospeed; the air pressure is related to the effortnecessary to turn the engine flywheel. Thesetting of the air pressure regulator can be upto 1030 kPa (150 psi) if necessary to get thecorrect cranking speed for a heavily loadedengine. With the correct setting, the airstarting motor can turn the heavily loadedengine as fast and as long as it can turn alightly loaded engine.

Other air supplies can be used if they have thecorrect pressure and volume. For good life ofthe air starting motor, the supply should befree of dirt and water. A lubricator with SAE10 non detergent oil [for temperatures above0°C (32°F)], or air tool oil, #1 diesel fuel orequivalent, [for temperatures below 0°C(32°F)] should be used with the startingsystem. The maximum pressure for use in theair starting motor is 760 kPa (110 psi).

Figure 50: Air Starting Motor(5) Air inlet. (6) Vanes. (7) Rotor. (8) Pinion. (9) Gears.(10) Piston. (11) Piston spring.

The air from the supply goes to relay valve(3). The start control valve (1) is connected tothe line before the relay valve. The flow of airis stopped by the relay valve until the startcontrol valve is activated. The air from startcontrol valve goes to piston (10) behind pinion(8) for the starting motor. The air pressure onthe piston puts spring (11) in compression andputs the pinion in engagement with theflywheel gear. When the pinion is inengagement, air can go out through anotherline to the relay valve. The air activates therelay valve which opens the supply line to theair starting motor.

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

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

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When the engine starts running, the flywheelwill start to turn faster than the starting motorpinion. The pinion retracts under thiscondition. This prevents damage to the motor,pinion or flywheel gear.

When start control valve (1) is released, theair pressure and flow to the piston behind thestarting motor pinion is stopped, the pistonspring retracts the pinion. The relay valvestops the flow of air to the air starting motor.

OilerAn air tube in the air passage through thebody of the oiler causes pressure above the oilin the bowl. Oil is sent from the bowl througha tube and passage to a chamber under the topplug on the body. From the chamber a flow ofoil goes through the oil drip orifice whichpermits a flow of oil of about four drops perminute.

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Engine Monitoring AndShutdown Protection

G3400 Engines can be configured to use oneof three systems to monitor engineparameters and provide engine shutdownprotection: Junction Box (Energize ToShutdown), Junction Box (Energize To Run),and/or a Control Panel (Status Control).

Junction Box

Figure 51: Junction Box (Shown With Door Open)(1) Terminal strips. (2) Status control module. (3)Emergency stop switch.

The junction box (Figure 51) provides acentral location to mount the various gauges,meters, indicators and switches available foruse on the engine. It also contains space forthe electrical terminal strips (1) that connectthe sensors, pick–ups and relays to the statuscontrol module (2). The junction box is alsoused to provide shutoff protection for theengine.

An Emergency Stop Push Button (ESPB) maybe located on the junction box panel. Whenthis button (3) is pressed, the fuel is shut offand the engine ignition is turned off (theground to the shutdown switch of theElectronic Ignition System control is opened).

To restart the engine, the ESPB must beturned until it pops out.

NOTICEThe Emergency Stop Push Button (ESPB) isnot to be used for normal engineshutdown. To avoid possible engine damage,use the Engine Control Switch (ECS) fornormal engine shutdown.

If the junction box is configured for anEnergized To Run (ETR) or an Energized ToShutoff (ETS) application, a gas shutoff valvewill be included in the engine installation. Inan Energize To Run set up, the gas shutoffvalve must remain energized to operate theengine. In the most common Energized ToShutoff system, the gas shutoff valve has amechanical (manual) latch that must be set. Ifa fault is detected, the gas shutoff valve will beenergized to unlatch the gas shutoff valve andstart a two stage shutoff sequence.

The junction box is used to monitor engine oilpressure, coolant temperature, starter motoroverspeed, and engine overspeed conditions.

Note: If the junction box monitors anoverspeed condition, or if the Emergency StopPush Button is activated, a relay will beenergized and cut ignition to the engine.

Note: If the junction box monitors a loss ofengine oil pressure, or detects a high coolanttemperature, a relay will shut the fuel off tothe engine.

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Figure 52: Engine Start/Stop Panel(1) Indicator lights. (2) Diagnostic reset plug. (3) Engine Control Switch. (ECS) (4) Status Control Module. (5)Emergency Stop Push Button (ESPB).

Engine Start/Stop Panel

Engine Control SwitchThe Engine Control Switch (ECS)(3) of thecontrol panel has four positions – “AUTO,MANUAL START, COOLDOWN/STOP,OFF/RESET”. See Figure 52. If the ECS is inthe “AUTO” position and a signal to run isreceived from a remote initiate contact (IC), orthe ECS is placed in the “MANUAL/START”position, the engine will crank, terminatecranking and run. Engines equipped withelectronic governors will run at low idle speeduntil lube oil pressure has exceeded the idlelow oil pressure set point, then the governorrelay contact of the Status Control Module willclose and the engine will accelerate to ratedspeed. Engines with hydra-mechanicalgovernors will accelerate to their speedsetting immediately after crank termination.The engine will run until the Engine ControlSwitch (ECS) is turned to“COOLDOWN/STOP”, “OFF/RESET”, or theremote initiate contact opens. Once the ECS ismoved to the “COOLDOWN/STOP” position, orif in the Auto position and the remote initiatecontact opens, the engine will run at a lowerspeed for a short period of time, if the cooldown feature was selected using the DDT. Ifthe cool down feature was not utilized theengine will shut down immediately. Theengine is then capable of immediate restart.

When the engine is to be shutdown, eithermanually (through the engine control switch)or automatically (through the engineprotection system), a two stage shutdownsequence will occur. First, a relay will de-energize the gas shutoff valve, and will shutthe fuel off to the engine. In the second step ofthe shutdown sequence the ground to theshutdown switch of the Electronic IgnitionSystem control is opened.

Emergency Stop Push ButtonAn Emergency Stop Push Button (ESPB)(5) islocated on the Engine Start/Stop Panel. Asecond Emergency Stop Push Button islocated on the engine itself (junction box),when a remote start/stop panel is used. Whenthis button is pressed, the fuel is shut off andthe engine ignition is turned off (the groundto the shutdown switch of the ElectronicIgnition System control is opened).

To restart the engine, ESPB must be turneduntil it pops out.

NOTICEThe Emergency Stop Push Button (ESPB) isnot to be used for normal engineshutdown. To avoid possible engine damage,use the Engine Control Switch (ECS) fornormal engine shutdown.

Status Control Module

Figure 53: Status Control Module (SCM).

The Engine Status Control Module (SCM)(Figure 53) is used to monitor engineparameters (oil pressure, coolant temperature,engine overspeed and over cranking of thestarting motor). It also provides an engineprotection system (two stage shutdown) andcontrols normal start/stop functions. When afault signal is detected, the display is also usedto indicate diagnostic codes, to aid introubleshooting.

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

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42

DC Control Panel for Gas Engine Chiller

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DC Control Panel for Gas Engine Chiller (Inside View)

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Appendix A

Abbreviations and Symbols

lekq7511 g3400 engine basics

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