Introduction

NOTE: For Specifications with illustrations, make reference to Specifications For 3176B Diesel Truck Engine, Form No. SENR5560. If the Specifications in Form No. SENR5560 are not the same as in the Systems Operation, 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.

Metric Fasteners

NOTE: Take care to avoid mixing metric and inch fasteners. Mismatched or incorrect fasteners can result in mechanical damage or malfunction, or possible personal injury. Original fasteners removed during disassembly should be saved for assembly when possible. If new ones are required, caution must be taken to replace with one that is of same part number and grade.

Metric thread fasteners are identified by material strength (grade) numbers on bolt heads and nuts. Numbers on bolts will be 8.8, 10.9, etc. Numbers on nuts will be 8, 10, etc.

Engine Design

Cylinder And Valve Location

Bore ... 125.025 ± 0.025 mm (4.9220 ± .0010 in)

Stroke ... 140 mm (5.5 in)

Displacement ... 10.3 liter (629 cu in)

Cylinder Arrangement ... in-line

Valves per Cylinder ... 4

Valve Lash Setting

Intake ... 0.38 mm (0.15 in)

Exhaust ... 0.64 mm (.025 in)

Compression Ratio ... 16 to 1, 16.25 to 1

Type of Combustion ... Direct Injection

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

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

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

General Information

The engine is an electronically controlled mechanically actuated unit injector diesel engine. The engine is an inline 6 cylinder arrangement with a bore of 125.025 mm (4.9220 in) and a stroke of 140 mm (5.5 in) giving a total displacement of 10.3 liter (629 cu in). The engine as configured is for air to air aftercooling. It is a low profile arrangement with the exhaust and inlet manifolds on the right hand side.

The electronic unit injector system eliminates many of the mechanical components of a "pump-in-line" system. It also provides increased control of timing and fuel/air ratio control. Timing advance is achieved by precise control of injector timing. Engine rpm is controlled by adjusting the injection duration. A special pulse wheel provides information to the electronic control module for detection of cylinder position and engine rpm.

The engine has built-in diagnostics to insure that all components are operating properly. In the event of a system component failure, the operator will be alerted to the condition via the dashboard mounted "check engine" light. A Caterpillar service tool can be used to read the numerical code of the faulty component or condition, or the cruise control switches can be used to "flash" the code on the dash mounted "check engine" light. Intermittent faults are "logged" and stored in memory.

Starting The Engine

The 3176B ECM will automatically provide the correct amount of fuel to start the engine. Do Not Hold The Throttle Down while cranking the engine. At temperatures below 0°C (32°F), it may be necessary to spray starting fluid into the air cleaner inlet. If the engine fails to start in 30 seconds, release the starter switch. Allow the starter motor to cool for two minutes before using it again.

Cold Mode Operation

The engine control system performs a cold start strategy for the correct warm up time after a cold engine start [approximately less than 17°C (63°F)]. Once activated this "cold start" strategy (known as "cold mode") will increase the idle rpm to 800 rpm, until the coolant temperature rises above 28°C (82°F), or until the engine has been running for 12 minutes. It also varies fuel injection amount and timing for maximum startup and white smoke control. The time needed for the engine to reach the normal mode of operation is usually less than the time taken for a walk-around-inspection of the vehicle.

After cold mode is completed, the engine should be operated at low rpm until normal operating temperature is reached. The engine will reach normal operating temperature faster when driven at low rpm and low power demand than when idled at no load. Typically, the engine should be up to operating temperature by just driving through the yard toward the open road.

Customer Specified Parameters

The engine is capable of being programmed for several customer specified parameters. It allows the owner to select horsepower ratings within a "family" to more efficiently match the vehicle to the application. This "Engine Power Rating", combined with the other available customer specified parameters, are generally programmed so the vehicle will achieve optimum fuel efficiency and operator convenience. For a complete list of the customer specified parameters see the topic: Electronic Control Module (ECM), and Personality Module. For a brief explanation of each of the customer specified parameters, see the Operation and Maintenance Manual.

Glossary Of 3176B Electronic Control Terms

After Market device

A device or accessory installed by the customer after the vehicle is delivered.

Air-To-Air Aftercooler (ATAAC)

A means of cooling intake air after the turbocharger, using ambient air for cooling. The intake air is passed through an aftercooler (heat exchanger) mounted in front of the radiator before going to the intake manifold.

Alternating Current (AC)

The type of current where the direction of current flow changes (alternates) regularly and constantly.

American Wire Gauge (AWG)

A measure of the diameter (and therefore the current carrying ability) of electrical wire. The smaller the AWG number, the larger the wire.

Before Top Center (BTC)

The 180 degrees of crankshaft rotation before the piston reaches Top Center (normal direction of rotation).

Boost Pressure Sensor

This sensor measures inlet manifold air pressure and sends a signal to the Electronic Control Module (ECM).

Bypass Circuit

A circuit, usually temporary, to substitute for an existing circuit, typically for test purposes.

Calibration

As used here for 3176B boost and timing, is an electronic adjustment of a sensor signal.

Cruise Control Range

The range within which the cruise control can operate. Usually limited to the speed range anticipated on the open road.

Code

See Diagnostic Code.

Customer Specified Parameters

A parameter that can be changed and whose value is set by the customer. Protected by customer passwords.

Data Link

An electrical connection for communication with other microprocessor based devices that are compatible with the proposed American Trucking Association and SAE Standard such as, trip recorders, electronic dashboards, and maintenance systems. The data link is also the communication medium used for programming and troubleshooting with Caterpillar service tools.

Desired RPM

An input to the electronic governor within the ECM. The electronic governor uses inputs from the Throttle Position Sensor, Engine Speed Sensor, Cruise Control, and Customer Parameters to determine "Desired RPM".

Desired Timing Advance ("Des Timing Adv" on ECAP)

The injection timing advance calculated by the ECM as required to meet emission and performance specifications.

Diagnostic Code

Sometimes referred to as a "fault code", it is an indication of a problem or event in the 3176B System.

Diagnostic Lamp

Sometimes referred to as the "check engine light", it is used to warn the operator of the presence of an active diagnostic code.

Direct Current

The type of current where the direction of current flow is consistently in one direction only.

Duty Cycle

See Pulse Width Modulation.

Electronic Control Analyzer and Programmer (ECAP)

A Caterpillar service tool used for diagnostic and programming functions

Electronic Control Module (ECM)

The engine control computer that provides power to the 3176B electronics, monitors 3176B inputs and acts as a governor to control engine rpm.

Electronically Controlled Unit Injector

The injection pump which is a mechanically actuated, electronically controlled unit injector combining the pumping, electronic fuel metering and injecting elements in a single unit.

Electronic Engine Control (3176B)

The complete electronic system that monitors and controls engine operation under all conditions.

Engine Speed/Timing Sensor

Provides a Pulse Width Modulated Signal to the ECM, which the ECM interprets as crankshaft position and engine speed.

Estimated Dynamic Timing

The ECM's estimate of actual injection timing.

Fuel Ratio Control (FRC)

FRC Fuel Pos. - is a limit based on control of the fuel-air ratio and is used for emissions control purposes. When the ECM senses a higher boost pressure (more air into cylinder), it increases the "FRC Fuel Pos" limit (allows more fuel into cylinder).

Fuel Position

An internal signal within the ECM from the Electronic Governor to fuel injection control, based on desired rpm, FRC fuel position, and rated fuel position (similar to Rack Position on 3406C Electronic Engine). See item "Electronic Control Signal Flow Chart".

Fuel Temperature Sensor

This sensor measures engine fuel temperature and sends a signal to the ECM.

Harness

The wiring bundle connecting all components of the 3176B System.

Hertz (Hz)

Measure of frequency in cycles per second.

Open Circuit

Condition where an electrical wire or connection is broken, so that the signal or the supply voltage can no longer reach its intended destination.

Original Equipment Manufacturer (OEM)

As used here, the manufacturer of a vehicle in which a Caterpillar engine is installed.

Parameter

A programmable value which affects the characteristics or behavior of the engine and/or vehicle.

Password

A group of numeric or alpha-numeric characters, designed to restrict access to parameters. The 3176B System requires correct passwords in order to change Customer Specified Parameters (Customer Passwords) or certain engine specifications (Factory Passwords). Passwords are also required to clear certain diagnostic codes.

Personality Module Or Ratings Personality Module

The module in the ECM which contains all the instructions (software) for the ECM and performance maps for a specific horsepower family.

Progressive Shifting

Shifting up through the lower gears quickly by not winding up the engine in each gear. Shifts are made above peak torque but below rated rpm. Needlessly winding up the engine into the higher rpm ranges before shifting to the next gear wastes fuel and fails to take advantage of the torque rise of the engine. The two steps (LoGr1, LoGr2) approximate ideal progressive shifting. Low Gear #1 is typically set no lower than Peak Torque RPM + 200 RPM. Low Gear #2 is typically set midway between Low Gear #1 RPM limit and Top Engine Limit.

Power Take Off (PTO)

Operated with the cruise control switches, this mode permits setting constant engine RPM when the vehicle is not moving (like a manual throttle control cable).

Pulse Width Modulation (PWM)

A signal consisting of variable width pulses at fixed intervals, whose "Time On" versus "Time Off" can be varied (also referred to as "duty cycly"). A PWM signal is generated by the Throttle Position Sensor.

Rated Fuel Position ("Rated Fuel Pos" on ECAP)

This indicates the maximum allowable fuel position (longest injection pulse). It will produce rated power for this engine configuration.

Reference Voltage

A regulated voltage supplied by the ECM to a sensor. The reference voltage is used by the sensor to generate a signal voltage.

Retarder Enable Signal

The retarder enable signal interfaces the ECM to the engine retarder. This prohibits operation of the engine brake under unsafe engine operating conditions (while fueling is taking place, etc).

Sensor

A device used to detect and convert a change in pressure, temperature, or mechanical movement into an electrical signal.

Service Program Module (SPM)

A software program on a factory programmable computer chip, designed to adapt an ECAP.

Short Circuit

A condition where an electrical circuit is unintentionally connected to an undesirable point. Example: a wire which rubs against a vehicle frame until it makes electrical contact.

Signal

A voltage or waveform used to transmit information, typically from a sensor to the ECM.

Speed "Burp"

A sudden brief change in engine speed.

Subsystem

As used here, it is a part of the 3176B System that relates to a particular function, for instance: vehicle speed subsystem, etc.

Supply Voltage

A constant voltage supplied to a component to provide electrical power for its operation. It may be generated by the ECM, or it may be vehicle battery voltage supplied by the vehicle wiring.

"T" Harness

A test harness designed to permit normal circuit operation while measuring voltages, typically inserted between the two ends of a connector.

Throttle Position

The ECM's interpretation of the signal from the throttle position sensor.

Throttle Position Sensor

An electronic sensor which is connected to the accelerator pedal and sends a Pulse Width Modulated Signal to the ECM.

Total Tattletale

Total number of changes to all customer specified parameters.

Transducer

A device that converts a mechanical signal to an electrical signal.

Vehicle Speed Sensor

An electro-magnetic pickup that measures vehicle speed from the rotation of gear teeth in the drive train of the vehicle.

Electronic Control System Components

Electronic Control System Components
(1) Fuel manifold. (2) Engine wiring harness. (3) Fuel transfer pump. (4) Electronic control module (ECM). (5) Personality module.

Electronic Control System Components
(6) Coolant temperature sensor. (7) Speed/timing sensor.

Major components of the electronic control system are: (1) Fuel manifold (2) Engine wiring harness, (3) Fuel transfer pump, (4) Electronic control module (ECM), (5) Personality module, (6) Coolant temperature sensor (located in the water temperature regulator housing), (7) Speed/timing sensor (in the right side of the front housing), and a throttle position sensor (remote mounted).

The electronic control system is integrally designed into the engines fuel system and air inlet and exhaust system to electronically control fuel delivery and injection timing. It provides increased control of timing and fuel/air ratio control in comparison to conventional mechanical engines. Injection timing is achieved by precise control of injector firing time, and engine rpm is controlled by adjusting the firing duration. The ECM energizes the fuel injection pump solenoids to start injection of fuel, and de-energizes the fuel injection pump solenoids to complete or stop injection of fuel. See the topic, Electronically Controlled Unit Injector, for a complete explanation of the fuel injection process.

The engine uses three types of electronic components which are: input, control and output.

An input component is one that sends an electrical signal to the electronic control module of the system. The signal sent varies in either voltage or frequency in response to change in some specific system of the vehicle (examples are: speed/timing sensor, coolant temperature sensor, cruise switches, etc.). The electronic control module sees the input sensor signal as information about the condition, environment, or operation of the vehicle.

A system control component receives the input signals. Electronic circuits inside the control evaluate the signals and supply electrical energy to the output components of the system in response to predetermined combinations of input signal values.

An output component is one that is operated by a control module. It receives electrical energy from the control group and uses that energy to either:

1) Perform work (such as a moving solenoid plunger will do) and thereby take an active part in regulating or operating the vehicle.

2) Give information or warning (such as a light or an alarm will do) to the operator of the vehicle or other person.

These components provide the ability to electronically control the engine operation to improve performance, minimize fuel consumption, and reduce emissions levels.

3176B Electrical Connectors And Functions

PID-FMI Flash Codes

Fuel System

Fuel System Schematic
(1) Siphon break passage. (2) Vent plug. (3) Pressure regulating orifice. (4) Electronically controlled unit injectors. (5) Fuel manifold (return path). (6) Fuel manifold (supply path). (7) Drain plug. (8) Fuel tank. (9) Check valve. (10) Pressure regulating valve. (11) Fuel transfer pump. (12) Electronic control module (ECM). (13) Fuel priming pump. (14) Fuel filter (secondary).

The fuel supply circuit is a conventional design for unit injected engines, in that it uses a fixed clearance gear type fuel transfer pump (11) to deliver fuel from the fuel tank to the electronically controlled unit injectors (4). Fuel is pulled from the fuel tank by the fuel transfer pump. The fuel transfer pump incorporates a check valve (9) to permit fuel flow around the gears for hand priming and a pressure regulating valve (10) to protect the system from extreme pressure. The excess fuel flow provided by the fuel transfer pump cools and purges the air from the unit injectors.

The fuel flows from the fuel transfer pump through cored passages in the housing of the electronic control module (ECM) (12) to cool the module, and then through a 5 micron filter (14) before entering the fuel supply manifold (6). A fuel priming pump (13) is located on the fuel filter base to fill the system after filter changes or after draining the fuel supply and return manifolds to replace unit injectors.

The fuel, to and from the unit injectors, passes through an adapter (siphon break) (1) mounted on the supply and return fuel manifold. The fuel flows continuously from the fuel supply manifold through the unit injectors when the supply or fill port in the injector is not closed by the injector body assembly plunger and is returned to the tank by the fuel return manifold (5). Fuel displaced by the plunger when not injecting fuel into the cylinder, is also returned to the tank by the fuel return manifold. For a complete explanation of the injection process, see the topic Electronically Controlled Unit Injector.

A pressure regulating orifice (3) is located in adapter manifold to maintain sufficient pressure in the system to fill the unit injectors.

Fuel System Components
(1) Adapter (siphon break). (5) Fuel return manifold. (6) Fuel supply manifold. (11) Fuel transfer pump. (12) Electronic control module (ECM). (13) Fuel priming pump. (14) Fuel filter. (15) Fuel outlet (to ECM). (16) Fuel inlet (from tank).

The fuel transfer pump is located at the left rear corner of the engine. It is mounted to a spacer block and is driven by the camshaft through a pair of helical gears. The check valve which permits fuel flow around the gears is located in the fuel transfer pump cover assembly.

Fuel Lines Group
(1) Adapter (siphon break). (3) Pressure regulating relief valve. (5) Fuel return manifold. (6) Fuel supply manifold. (11) Fuel transfer pump. (12) ECM. (13) Fuel priming pump. (14) Fuel filter. (17) Fuel supply manifold. (18) Plug. (19) Fuel out (from ECM). (20) Fuel in. (21) Air bleed plug.

The fuel supply and return manifolds are drilled passages in a common manifold which is mounted to the cylinder head. Fuel from the fuel supply manifold (17) flows through drilled passages within projections in the cylinder head casting, and into the unit injectors.

At the end of the fuel return manifold is a pressure regulating orifice (3) which is a part of adapter (siphon break) (1). The pressure regulating orifice maintains pressure to fill the unit injectors.

Fuel System Electronic Control Circuit

3176B RPM Control Logic

3176B Electronic Governor

The injection pump, fuel lines and nozzles used in traditional Caterpillar Diesel Engines have been replaced with an electronically controlled, mechanically actuated unit injector in each cylinder. A solenoid on each injector controls the amount of fuel delivered by the injector. An Electronic Control Module (ECM) sends a signal to each injector solenoid, to provide complete control of the engine.

Electronic Controls

The 3176B Diesel Truck Engine Electronic Control System consists of two main components: the Electronic Control Module (ECM) and the Personality Module. The ECM is the computer and the personality module is the software for the computer (the personality module also stores the operating maps that define horsepower, torque curves, rpm, etc). The two work together (along with sensors to "see" and solenoid/injectors to "act") to control the engine. Neither one can do anything by itself.

The ECM determines a "desired rpm" based on the throttle signal, vehicle speed signal (only while in cruise), PTO switches (only while in cruise or PTO) and certain diagnostic codes. The ECM then maintains the desired engine rpm by sensing actual engine rpm and deciding how much fuel to inject in order to achieve the desired rpm.

Fuel Injection

The ECM controls the amount of fuel injected, by varying signals to the injectors. The injectors will inject fuel ONLY if the injector solenoid is energized. The ECM sends a 90 volt signal to the solenoid to energize it. By controlling the timing and duration of the 90 volt signal, the ECM can control injection timing and the amount of fuel injected.

The ECM sets certain limits on the amount of fuel that can be injected. "FRC Fuel Pos" is a limit based on boost pressure to control the fuel-air ratio, for emissions control purposes. When the ECM senses a higher boost pressure (more air into cylinder), it increases the "FRC Fuel Pos" limit (allows more fuel into cylinder). "Rated Fuel Pos" is a limit based on the horsepower rating of the engine. It is similar to the rack stops and torque spring on a mechanically-governed engine. It provides horsepower and torque curves for a specific engine family and rating. All of these limits are programmed by the factory into the Personality Module and are not programmable in the field.

Injection timing depends on engine rpm, load, and other operation factors. The ECM knows where top-center of cylinder number one is from the signal provided by the engine Speed/Timing Sensor. It decides when injection should occur relative to top-center and provides the signal to the injector at the desired time.

Unit Injector Mechanism

Unit Injector Mechanism
(1) Adjusting nut. (2) Rocker arm assembly. (3) Electronically controlled unit injector. (4) Push rod. (5) Cylinder head. (6) Spacer block. (7) Camshaft. (8) Lifter.

The unit injector mechanism provides the downward force required to pressurize the fuel in the unit injector pump. The electronically controlled unit injector (3), at the precise time, allows fuel to be injected into the combustion chamber. The camshaft gear is driven by an idler gear which is piloted in the cylinder block and bolted through the timing gear housing to the block. The idler gear is driven by the crankshaft gear. Timing marks on the crankshaft gear, idler gear, and camshaft gear are aligned to provide the correct relationship between piston and valve movement. The camshaft has three cam lobes for each cylinder. Two lobes operate the intake and exhaust valves, and one operates the unit injector mechanism. Force is transmitted from the unit injector lobe on camshaft (7), through lifter (8), to pushrod (4). From the push rod, force is transmitted through rocker arm assembly (2) and to the top of the unit injector pump. The adjusting nut (1) allows setting of the injector lash. See the topic, Injector Lash Adjustment, in the Testing and Adjusting Section for proper setting of the injector lash.

Electronically Controlled Unit Injector

Electronically Controlled Unit Injector
(1) Solenoid connection (to the multiplex enable circuit). (2) Solenoid valve assembly. (3) Spring. (4) Valve (shown in the closed position). (5) Plunger. (6) Barrel. (7) Seal. (8) Seal. (9) Spring. (10) Spacer. (11) Body. (12) Check.

Low pressure fuel from the fuel supply manifold (through drilled passages in the cylinder head), enters the electronically controlled unit injector at the fill port. As the unit injector mechanism produces force to the top of the unit injector, spring (3) is compressed, and plunger (5) is driven downward, displacing fuel through valve (4) into the return manifold to the tank. The fill passage into barrel (6) is closed by the outside diameter of the plunger, and the passages within body (11) and along check (12) to the injector tip are filled with fuel as the plunger moves down. After the fill passage in the plunger barrel is closed, fuel can be injected at any time depending on the start of injection timing requirements programmed into the electronic control module.

When solenoid valve assembly (2) is energized, from a signal across solenoid connection (1), valve (4) closes and pressure is elevated in the injector tip. Injection starts at 37 931 kPa (5500 psi), as the force of spring (9) above spacer (10) is overcome and the check lifts from its seat. The pressure continues to rise as the plunger cycles through its full stroke. After the correct amount of fuel has been discharged into the cylinder, the electronic control module signals across the solenoid connection, the solenoid valve assembly is de-energized and valve (4) is opened. Now, the high pressure fuel is dumped through the spill port to the fuel return manifold and tank. The check in the injector tip seats and injection is ended, as the fuel pressure decreases to 25 517 kPa (3700 psi) and below.

The length of injection meters the fuel consumed during the cylinder fuel injection. Injection length is controlled by the governor logic programmed into the electronic control module of the fuel system electronic control circuit.

After reaching the maximum lift point, the force to the top of the unit injector is removed as spring (3) expands. The plunger returns to its original position, uncovering the fuel supply passage into the plunger barrel to refill the injector pump body. Low pressure fuel then circulates through the injector body and out the spill port until the solenoid valve assembly (2) is again energized

Air Inlet and Exhaust System

Air Inlet and Exhaust System Schematic
(1) Aftercooler. (2) Air inlet. (3) Turbocharger compressor wheel. (4) Intake valves. (5) Exhaust valves. (6) Turbocharger turbine wheel. (7) Exhaust outlet. (8) Inlet manifold. (9) Exhaust manifold.

Air Inlet and Exhaust System Components
(2) Air inlet. (7) Exhaust outlet. (8) Inlet manifold. (9) Exhaust manifold. (10) Valve mechanism cover. (11) Turbocharger. (12) Oil inlet line. (13) Oil drain line.

The engine components of the air inlet and exhaust system control the quality and the amount of air available for combustion. They are located on the right hand side of the engine and arranged for air-to-air aftercooling. These components include all of those shown in the illustration, plus an air cleaner.

Inlet air is pulled through the air cleaner into air inlet (2) by turbocharger compressor wheel (3). Here the air is compressed and heated, and forced on to aftercooler (1) which is mounted in front of the engine radiator. The air flows through the aftercooler, lowering the temperature of the compressed air. Cooling of the inlet air increases combustion efficiency, which helps lower the fuel consumption and increase the horsepower output.

From the aftercooler, air is forced into inlet manifold (8). Air flow from the inlet chambers (there are three of them) into the cylinders is controlled by intake valves (4). There are two intake valves and two exhaust valves (5) in the cylinder head for each cylinder. Intake valves open when the piston moves down on the inlet stroke. When the intake vales open, cooled compressed air from the inlet chamber within the inlet manifold is pulled into the cylinder. The intake valves close and the piston begins to move up on the compression stroke.

The air in the cylinder is compressed, and when the piston is near the top of the compression stroke, fuel is injected into the cylinder. The fuel mixes with the air and combustion starts. The force of combustion pushes the piston down on the power stroke. The exhaust valves open and the exhaust gases are pushed through the exhaust port into exhaust manifold (9). After the piston makes the exhaust stroke, the exhaust valves close and the cycle (inlet, compression, power, exhaust) starts again.

Exhaust gases from the exhaust manifold flow into the turbine side of the turbocharger, and cause turbocharger turbine wheel (6) to turn. The turbine wheel is connected to the shaft that drives the compressor wheel. Exhaust gases from the turbocharger pass through exhaust outlet (7), a muffler and an exhaust stack.

Turbocharger

Turbocharger (11) is mounted to exhaust manifold (9) of the engine. All the exhaust gases go from the exhaust manifold through the turbocharger.

Turbocharger Cartridge
(3) Turbocharger compressor wheel. (6) Turbocharger turbine wheel. (15) Ring. (16) Housing assembly. (17) Bearing. (18) Oil inlet port. (19) Ring. (20) Deflector. (21) Oil outlet port. (22) Ring. (23) Bearing. (24) Ring.

The exhaust gases go into the turbocharger and push the blades of turbocharger turbine wheel. Since the turbocharger turbine wheel is connected by shaft to the turbocharger compressor wheel, this causes the turbine wheel and compressor wheel to turn at very high speeds. Clean air from the air cleaner is pulled through the compressor housing air inlet by rotation of the compressor wheel. 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 more air and fuel during combustion.

When the load on the engine increases, or a greater engine speed is desired, more fuel is injected into the cylinders. This makes more exhaust gases, and will cause the turbine and compressor wheels of the turbocharger to turn faster. As the compressor wheel turns faster, more air is forced into the engine. The increased flow of air gives the engine more power because it makes it possible for the engine to burn the additional fuel with greater efficiency.

Maximum rpm of the turbocharger is controlled by the electronic fuel system circuit. Programming of the fuel amount available is done in the personality module at the factory for a specific engine application.

Bearings (17) and (23) in the turbocharger use engine oil under pressure for lubrication. The oil flows through oil inlet line (12) and into oil inlet port (18) in the center section for lubrication of the bearings. Oil leaves the turbocharger through oil outlet port (21) and oil drain line (13), returning to the engine block.

Valves and Valve Mechanism

Valve Mechanism
(1) Intake bridge. (2) Rotocoil. (3) Intake rocker arm. (4) Push rod. (5) Valve springs (inner and outer). (6) Intake valves. (7) Valve guide. (8) Camshaft. (9) Lifter.

The valves and valve mechanism control the flow of inlet air and exhaust gases into and out of the cylinders during engine operation. The intake and exhaust valves are opened and closed by the valve mechanism as rotation of the crankshaft causes rotation of camshaft (8). The camshaft gear is driven by an idler gear which is piloted in the cylinder block and bolted through the timing gear housing to the block. The idler gear then is driven by the crankshaft gear. Timing marks on the crankshaft gear, idler gear, and camshaft gear are aligned to provide the correct relationship between piston and valve movement.

The camshaft has three cam lobes for each cylinder. Two lobes operate the intake and exhaust valves, and one operates the unit injector mechanism. As the camshaft turns, the intake cam lobe causes lifter (9) to move push rod (4) up and down. Upward movement of the pushrod against intake rocker arm (3) transmits a downward force on intake bridge (1) and a downward movement on the two intake valves (6), opening them. The intake bridge moves up and down on a dowel mounted in the cylinder head.

Each cylinder has two intake and two exhaust valves. Two valve springs (5) for each valve hold the valves in the closed position when the lifter moves down (away from the cam lobe as the camshaft turns).

Valves-No. 1 And No. 2 Cylinders (intake, exhaust, and unit injector rocker arms removed from no. 2 cylinder)
(1) Intake bridge. (2) Rotocoil. (3) Intake rocker arm (of the adjoining cylinder). (6) Intake valves. (10) Exhaust rocker arm. (11) Exhaust bridge. (12) Exhaust valves.

Rotocoils (2) cause the valves to rotate while the engine is running. This rotation of the valves keeps the deposit of carbon on the valves to a minimum and gives the valves longer service life.

Jake Brake (an attachment)

The Jake Brake is powered from the ECM and aids the operator in slowing and controlling the vehicle on grades and curves, or anytime when speed reduction is necessary, but long applications of the service brakes are not desired. In downhill operation, or any slow down condition, the engine crankshaft is turned by the rear wheels (through the differential, driveshaft, transmission, and clutch). To reduce the speed of the vehicle, an application of a braking force can be made to the pistons of the engine.

When the Jake Brake is activated, braking power is accomplished by opening the engine's exhaust valves near the top of the compression stroke to release the highly compressed air, with the energy it represents, into the exhaust system. No combustion occurs to produce positive force on the piston since the Jake Brake can only be activated (providing the retarding or slowing effect) when the engine is in a "no fuel" mode.

The release of the compressed air pressure to the atmosphere prevents the return of energy to the engine piston on the expansion (power) stroke. The result is an energy loss, since the work done by the compression of the cylinder charge is not returned by the expansion process. This energy loss is taken from the rear wheels, which provides the braking action for the vehicle.

Jake Brake Installed (one Jake Brake housing assembly shown)
(1) Control valve. (2) Lead wire connection (from Jake Brake logic to solenoid valve). (3) Headbolt stud, spacer, and bolt. (4) Slave piston. (5) Solenoid valve. (6) Master piston. (7) Stud and nut.

Exhaust Bridge Assembly
(8) Plunger assembly. (9) Bridge assembly.

The Jake Brake consists of three identical housing assemblies, one installed in each of the valve mechanism compartments above the rocker arms and rocker arm shaft. Each housing assembly is positioned over two cylinders. It is mounted to the rocker arm shaft supports with studs and nuts (7), and supported on the cylinder head with stud, spacer, and bolt (3).

The exhaust bridge assembly is used to transmit force from slave piston (4) to the exhaust valve. A lead wire carries the Jake Brake logic signal to solenoid valve (5) to activate the Jake Brake operation on two cylinders of the engine.

NOTE: Only the engine valves and valve mechanism for the exhaust side of the cylinders are used in the operation of the Jake Brake.

A spacer is used on top of the valve cover base to provide space for installation of the Jake Brake and valve cover. The increase in height with the Jake Brake installed is approximately 63.5 mm (2.50 in).

Each Jake Brake housing assembly and mounting hardware consists of: two control valves (1), one wire harness (2), one headbolt stud, spacer, and bolt (3), slave pistons (4), one solenoid valve (5), two master pistons (6), two exhaust bridge assemblies, and two studs, and nuts (7).

The plunger assembly (8) in the bridge is non-adjustable. See the topic, Jake Brake Adjustment in Testing and Adjusting, for a complete description of the exhaust bridge assembly adjustment.

NOTE: On this engine only one of the two exhaust valves for each cylinder is used in the Jake Brake operation.

The Jake Brake control circuit permits operation of either one, two, or all three of the Jake Brake housing assemblies, thus providing progressive braking capability with the retarding power of either two, four, or all six cylinders of the engine.

Jake Brake Performance

Jake Brake Performance (horsepower versus engine rpm)

The Jake Brake's performance shown in the graph represents an engine operating with all three of the Jake Brake housing assemblies activated to brake the vehicle. The Jake Brake should not be activated when the engine rpm is over 2300. At 2100 rpm, the maximum engine power rating, the amount of braking produced by the Jake Brake is approximately 315 horsepower.

Jake Brake Operation

Master-Slave Circuit Schematic
(1) Lead wire (from Jake Brake logic to solenoid valve). (2) Solenoid valve. (3) Master piston. (4) Slave piston. (5) Control valve. (6) Exhaust bridge assembly. (12) Spring. (13) High pressure oil passage. (14) Slave piston adjustment screw. (15) Rocker arm shaft oil passage. (16) Engine oil pump. (17) Spring. (18) Injector rocker arm. (19) Injector push rod. (20) Exhaust valve. (21) Engine oil pan. (22) Oil drain passage. (23) Low pressure oil passage. (24) Ball check valve. (25) Exhaust valve rocker arm.

The Jake Brake operates with engine oil which is supplied around the studs through the rocker arm shaft supports. Solenoid valve (2) controls the oil flow in the Jake Brake housing assembly.

When the solenoid is activated by a signal from the Jake Brake logic, solenoid valve (2) moves down and closes oil drain passage (22) to engine oil pan (21). At the same time, it opens low pressure oil passage (23) to control valve (5). As the low pressure oil passage (23) is filled with engine oil, the control valve is pushed up in its chamber against the force of spring (12). At this position, a groove in the control valve (5) is in alignment with high pressure oil passage (13) that supplies slave piston (4) and master piston (3).

Engine oil pressure will now lift ball check valve (24) and fill the high pressure oil passage (13) and the chambers behind the slave and master pistons. This pressure moves the master piston downward until it makes contact with the injector rocker arm (18). As soon as upward motion is initiated on the master piston, pressure is increased above engine supply pressure, thereby seating the ball check valve (24). The system is now in operation in conjunction with the exhaust valve and injector rocker mechanism. When the solenoid is activated, the Jake Brake is ready to operate in approximately 1/5 of a second.

When injector push rod (19) begins to move up on the electronically controlled unit injector's pumping stroke, injector rocker arm (18) makes contact with the extending master piston (3). As the master piston begins to move up, the oil pressure increases in the high pressure oil passage (13) because the ball check valve (24) will not let the oil out. Since there is a constant increase in pressure with the injector rocker arm upward movement, the slave piston is forced down against the pin and screw assembly in Jake Brake exhaust bridge assembly (6) (of the same cylinder) with enough force to open exhaust valve (20).

This master-slave circuit is designed so that the master piston (3) is only moved when the engine cylinder is on the compression stroke, and the slave piston (4) opens one exhaust valve of the same cylinder only on the compression stroke (just before the piston reaches top center). The braking force is constant, and since the Jake Brake operation of a given cylinder is caused by the valve mechanism motion of that same cylinder, the sequence is the same as the firing order of the engine.

When solenoid valve (2) is in the off position, the engine oil supply passage is closed, and oil drain passage (22) is opened. This lets oil drain from beneath control valve (5), and spring (12) pushes the control valve to the bottom of the chamber. This position lets oil from high pressure oil passage (13) drain into the chamber above the control valve piston (chamber vents to atmosphere outside of the Jake Brake housing). Spring (17) now moves the master piston (3) up to its retracted position, away from injector arm (18). The time necessary for the system to stop operation is approximately 1/10 of a second. The Jake Brake will not be able to operate now until the solenoid (2) is activated again.

Lubrication System

Lubrication System Schematic
(1) Piston cooling jets. (2) Main oil gallery (in cylinder block). (3) Engine oil pressure sensor. (4) Oil flow to valve mechanism. (5) Camshaft journals. (6) Oil filter bypass valve. (7) Main bearings. (8) Signal line. (9) Oil filter (full flow). (10) Oil pump. (11) Bypass oil filter. (12) Oil cooler bypass valve. (13) Oil cooler. (14) Oil pan (sump). (15) High pressure relief valve. (16) Oil pump bypass valve.

Engine-Right Side
(9) Oil filter (full flow). (10) Oil pump. (11) Bypass oil filter. (13) Oil cooler. (17) Oil filler. (18) Oil supply line to turbocharger (from cylinder block). (19) Oil drain line from turbocharger (to cylinder block).

The lubrication system supplies 110°C (230°F) filtered oil at approximately 275 kPa (40 psi) at rated engine operating conditions. An oil pump bypass valve (16), is controlled by engine oil manifold pressure rather than the oil pump pressure. The oil manifold pressure then becomes independent of the oil filter and oil cooler pressure drop.

The oil cooler bypass valve (12) is thermostatic controlled to maintain 110°C (230°F) oil to bearing temperature. The high pressure relief valve (15), located in the filter base, protects the filters and other components during cold starts. The high pressure relief valve opening pressure is 695 kPa (100 psi) pressure. The bypass oil filter (11) is a continuous flow 5 micron filter that returns 5 percent of the oil flow to the sump (14). The oil filter bypass valve opening pressure is 170 kPa (25 psi). An engine oil pressure sensor is part of the Electronic Engine Protection Package. Another feature of the lubrication system is that the symmetrical oil pan can be installed as front or rear sump.

The turbocharger cartridge bearings are lubricated by oil supply line (18) (from the main oil gallery), and oil drain line (19) returns the oil flow to the sump.

Oil Flow Through The Lubrication System

Oil Filter Group
(1) Oil flow (to the piston cooling jets, valve mechanism, camshaft journals, crankshaft main bearings, and to the turbocharger). (2) Main oil gallery (in cylinder block). (3) Oil drains to sump. (4) Cylinder block. (5) Oil from oil cooler. (6) High pressure relief valve. (7) Oil from oil pump. (8) Oil to oil cooler. (9) Passage to main oil filter. (10) Filtered oil. (11) Bypassed oil. (12) Oil filter bypass valve. (13) Passage to main oil filter. (14) Oil cooler bypass valve. (15) Oil pump bypass valve. (16) Oil pump bypass drain. (17) Passages to bypass filter.

The oil pump is mounted to the back of the front gear train on the lower right hand side of the engine. It is driven by an idler gear from the crankshaft gear. Oil is pulled from the sump through oil pump bypass valve (15) on its way to the oil cooler. The bypass valve controls the oil pressure from the oil pump. The oil pump can provide more oil into the lubrication system than is needed. When this situation is present, the oil pressure increases and the bypass valve opens, allowing the excess oil to return to the sump.

High pressure relief valve (6) regulates high pressure in the system and will allow oil to return to the sump when the oil pressure reaches or exceeds 695 kPa (100 psi). The oil flow continues to the oil cooler which has coolant flowing through it to cool the oil. The thermostat controlled oil cooler bypass valve (14) directs the oil flow through the oil cooler when the oil temperature reaches 100 to 102.8°C (212 to 217°F). A fail safe activation temperature [126.7°C (260°F)] incorporated in the valve will close the valve, directing oil flow to the oil cooler. The valve will remain at this position since it has failed. The bypass valve is also pressure activated. If oil pressure differential across the oil cooler reaches 155 ± 17 kPa (22 ± 2.5 psi), the valve will open and allow oil flow to bypass the oil cooler.

Approximately five percent of the oil flow is directed through an orifice [passage to bypass filter (17))], then through the bypass filter and to the sump. The main oil flow now reaches the main oil filter. When the oil pressure differential across the oil filter bypass valve (12) reaches 170 kPa (25 psi), the valve allows the oil flow to go around the main oil filter and on to lubricate the engine parts. When the oil is cold, an oil pressure difference in the bypass valve also causes the valve to open. This bypass valve then provides immediate lubrication to all the engine components when cold oil with high viscosity causes a restriction to the oil flow through the oil filter. The bypass valve will also open when there is a restriction in the oil filter. This action does not let an oil filter with a restriction prevent lubrication of the engine.

NOTE: See the topic, Oil Filter Group in the Specifications, for a cross section of the oil filter group valves.

Filtered oil flows through the main oil gallery in the cylinder block. From here the piston cooling jets, valve mechanism, camshaft bearings, crankshaft main bearings, and the turbocharger cartridge are lubricated.

Interior Of Cylinder Block (with oil pan and underframe removed)
(18) Piston cooling jet. (19) Piston. (20) Connecting rod.

An oil cooling chamber is formed by the lip forge at the top of the skirt of the piston and the cavity behind the ring grooves in the crown. Cooling jet oil flow enters the cooling chamber through a drilled passage in the skirt and returns to the sump through the clearance gap between the crown and skirt. Four holes drilled from the piston oil ring groove to the interior of the piston drain excess oil from the oil ring.

Engine-Front Left Side
(21) Breather. (22) Hose. (23) Cylinder head.

Breather (21) allows blowly gases from the cylinders during engine operation to escape from the crankcase. The blowby gases flow or discharge through hose (22) into the atmosphere. This prevents pressure from building up that could cause seals or gaskets to leak.

Cooling System

Cooling System Schematic
(1) Temperature regulator housing. (2) Radiator. (3) Bypass tube. (4) Water pump. (5) Oil cooler. (6) Return manifold. (7) Supply manifold.

A gear driven water pump located in the right hand side of the engine supplies the coolant for the engine cooling system. The coolant is supplied to the oil cooler, cylinder head, cylinder liner, air compressor (not shown), and a coolant conditioner (an attachment).

NOTE: In air to air aftercooled systems, a coolant mixture with a minimum of 30 percent ethylene glycol base antifreeze must be used for efficient water pump performance. This mixture keeps the cavitation temperature range of the coolant high enough for efficient performance. Dowtherm 209 Antifreeze can not be used because it does not raise the water pump cavitation temperature of the coolant high enough.

Engine-Right Side
(1) Temperature regulator housing. (4) Water pump. (5) Oil cooler. (9) Coolant to oil cooler from water pump.

Engine-Rear
(6) Return manifold.

Engine-Right Side
(7) Supply manifold. (8) Coolant from oil cooler to supply manifold.

Coolant Flow

Coolant is pulled from the bottom of radiator (2) into water pump (4) by impeller action. The water pump is located on the cylinder block side of the front timing gear housing on the right hand side of the engine. It is gear driven, at 1.14 times engine speed by an idler which is turned by the crankshaft gear. The water pump shaft is supported by two ball bearings located in the water pump housing and front timing gear cover. The water pump impeller is a closed face, radial vane cast iron design. The water pump housing and volute housing are aluminum die castings. A cartridge type water pump seal is located on the inlet side of the pump to provide good water flow around the seal for cooling. It can be replaced by removing the volute housing and pulling the impeller from the shaft.

The coolant is pumped through oil cooler (5) and into supply manifold (7). The supply manifold, located in the spacer block, distributes coolant at each cylinder that flows around and cools the upper portion of the cylinder liner. At each cylinder coolant flow from the liner enters the cylinder head that is divided into single cylinder cooling sections. In the cylinder head coolant flows across the center of the cylinder and the injector seat boss. At the center of the cylinder coolant flow up around the injector sleeve over the exhaust port and exits into return manifold (6). The return manifold collects the coolant from each cylinder and directs the flow to temperature regulator housing (1). With the temperature regulator in the closed position, coolant flows through the regulator, bypassing the radiator, and back to the water pump for recirculation. With the temperature regulator in the open position, the coolant is directed through the radiator and back to the water pump inlet.

Supply Manifold

Supply Manifold
(7) Supply manifold (part of spacer block; access cover removed). (10) Slits.

Cooling is provided for only the portion of the cylinder liner above the seal in the spacer block. Coolant enters the spacer block at each cylinder through slits (10) in supply manifold (7). The supply manifold is an integral casting in the spacer block. The coolant flows around the circumference of the cylinder liner and into the cylinder head through a single drilled passage for each liner. The coolant flow is split at each liner so that 65 percent flows around the liner and the remainder bypasses the liner and flows directly to the cylinder head.

Temperature Regulator Housing

Engine-Front Right Side
(1) Temperature regulator housing. (3) Bypass tube. (11) Outlet to radiator. (12) Coolant temperature sensor.

Temperature Regulator Housing
(6) Return manifold. (13) Closed position.

The coolant temperature regulator is the full flow bypass type installed for outlet temperature regulation of the coolant. With the valve in closed position (13), the engine is cold, the coolant flows through the regulator [from return manifold (6)], bypassing the radiator, and back to the water pump inlet for recirculation. As the coolant temperature increases, the temperature regulator begins to open directing some of the coolant to the radiator and bypassing the remainder to the water pump inlet. At full operating temperature of the engine, the valve moves to the open position, and all the coolant flow is directed to the radiator and then back to the water pump inlet providing maximum heat release from the coolant. A vent line is recommended from the manifold to the shunt tank to provide cooling system venting (#4 Aeroquip is recommended size).

Coolant for Air Compressor

Coolant Flow for Air Compressor
(1) Inlet hose. (2) Outlet hose. (3) Air compressor.

The coolant used for the air compressor (3) comes from the cylinder block through inlet hose (1). The coolant leaves the air compressor through outlet hose (2) and flows back to the cylinder head.

Coolant Conditioner (An Attachment)

Coolant Conditioner Group
(1) Temperature regulator housing. (2) Inlet hose. (3) Outlet hose. (4) Coolant flow to spacer block. (5) Oil cooler. (6) Coolant flow from water pump. (7) Coolant conditioner element. (8) Coolant conditioner base.

Some conditions of operation have been found to cause pitting (small holes in the metal surface) from corrosion or cavitation erosion (wear caused by bubbles in the coolant) on the outer surface of the cylinder liners and the inner surface of the spacer block next to the liners. The addition of a corrosion inhibitor (a chemical that gives a reduction of pitting) can keep this type of damage to a minimum.

The "spin-on" coolant conditioner element (7), similar to fuel filter and oil filter elements, fasten to the coolant conditioner base (8) that is mounted on the engine. Coolant flows from the oil cooler (5), through inlet hose (2), into the coolant conditioner base. The "conditioned" or treated coolant then flows through outlet hose (3) into the temperature regulator housing (1). There is a constant flow through the coolant conditioner element.

The element has a specific amount of inhibitor for acceptable cooling system protection. As coolant flows through the element, the corrosion inhibitor, which is a dry material, dissolves (goes into solution) and mixes to the correct concentration. Two basic types of elements are used for the cooling system, the "Precharge" and the "Maintenance" elements. Each type of element has a specific use and must be used correctly to get the necessary concentration for cooling system protection.

The elements also contain a filter and should be left in the system so coolant flows through it after the conditioner material is dissolved.

The "Precharge" element has more than the normal amount of inhibitor, and is used when a system is first filled with new coolant. This element has to add enough inhibitor to bring the complete cooling system up to the correct concentration.

The "Maintenance" elements have a normal amount of inhibitor and are installed at the first change interval. They provide enough inhibitor to keep the corrosion protection at an acceptable level. After the first change period, only "Maintenance" elements are installed at specified intervals to give protection to the cooling system.

Basic Block

Cylinder Block And Head

The cylinder block is a unique two piece design consisting of an aluminum spacer block and a gray iron crankcase. The spacer block forms the upper portion of the cylinder block and provides the cylinder liner coolant jacket and camshaft support.

The cylinder liner is a mid-supported design seated on the top face of the crankcase and piloted below the seat and at the bottom in the crankcase. Sealing of the liner is above the seating surface by a rectangular cross section seal located in a groove machined in the spacer block. The seal groove is located in the spacer block to minimize liner distortion when the liner is clamped between the cylinder head and crankcase. Cooling is provided for only the portion of the liner above the seal in the spacer block.

The cast iron crankcase provides the seat and locating bores for the cylinder liners and supports the crankshaft. All threaded holes for fastening the cylinder head, flywheel housing, front timing gear housing and front engine support are in the crankcase portion of the cylinder block.

Two oil manifolds are provided in the cylinder block for engine lubrication. The lower right side manifold in the crankcase supplies oil for the piston cooling jets and the crankshaft bearings. The upper left side manifold in the spacer block supplies oil for the camshaft bearings and valve mechanism. The oil supply for the left side manifold is from the right side manifold through a drilled passage in the front bulkhead of the crankcase. Both manifolds are cast solid and rifle drilled.

Pistons, Rings And Connecting Rods

The piston is a two piece articulated design consisting of a forged steel crown and a forged aluminum skirt. Both parts are retained by the piston pin to the small end of the connecting rod. An oil cooling chamber is formed by the lip forge at the top of the skirt of the piston and the cavity behind the ring grooves in the crown. Cooling jet oil flow enters the cooling chamber through a drilled passage in the skirt and returns to the sump through the clearance gap between the crown and skirt. The pistons have three rings located in grooves in the steel crown to seal combustion gas and provide oil control. The top ring is a barrel faced KEYSTONE type with plasma face coating. The second ring is taper faced and has a chrome plated face coating. The third ring, oil ring, is double railed, profile ground, and chromed face coated. The third ring has a coil spring expander. Four holes drilled from the piston oil ring groove to the interior of the piston drain excess oil from the oil ring.

The connecting rod is a conventional design with the cap fastened to the shank portion by two bolts threaded into the shank. Each side of the small end of the connecting rod is machined at an angle of 12 degrees to fit within the piston cavity allowing maximum utilization of the available space for gas load.

Crankshaft

The crankshaft converts the cylinder combustion forces into rotating torque which powers equipment. On this engine, a vibration damper 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 (front gear train) on the front of the engine. The front gear train provides power for the camshaft, water pump, oil pump, air compressor, and hydraulic pump.

The crankcase has seven main bearings to support the crankshaft, with two bolts holding the bearing cap to the block. Oil holes and grooves in the upper bearing shell are located at main bearing journals 2, 3, 5, and 6 to supply oil to the connecting rod bearings. The center and end main journals and bearings are not drilled or grooved to provide the maximum oil film thickness possible at these more critical locations. The crankshaft has eight integral forged counterweights located at cheeks 1, 2, 5, 6, 7, 8, 11 and 12.

To seal the crankshaft, flange mounted dual lip teflon seals with hydrodynamic grooving running on induction hardened crankshaft wear surfaces are used. The seals are assembled to the front timing gear cover and rear seal housing with bolts and a rubber O-ring to seal the flange.

Camshaft

The camshaft has three lobes at each cylinder to operate the unit injector, exhaust valves, and the intake valves. The camshaft is supported in the spacer block in seven "as machined" bores, and is driven by an idler gear turned by the crankshaft in the front gear train. Each bearing journal is lubricated from the oil manifold in the spacer block. A thrust pin located at the rear, supported by the spacer block, positions the camshaft through a circumferential groove machined back of the fuel transfer pump drive gear. Timing of the camshaft is accomplished by aligning marks on the crankshaft gear, idler gear, and camshaft gear with each other.

Electrical System

Reference

For the complete 3176B electrical system schematic, refer to electrical system schematic in 3176B & 3406E Electronic Troubleshooting, Form No SENR5574.

Grounding Practices

Proper grounding for vehicle and engine electrical systems is necessary for proper vehicle performance and reliability. Improper grounding will result in uncontrolled and unreliable electrical circuit paths.

Uncontrolled engine electrical circuit paths can result in damage to main bearings, crankshaft journal surfaces, and aluminum components.

Uncontrolled electrical circuit paths can cause electrical noise which may degrade vehicle and radio performance.

To insure proper functioning of the vehicle and engine electrical systems, an engine-to-frame ground strap with a direct path to the battery must be used. This may be provided by way of a starter motor ground, a frame to starter motor ground, or a direct frame to engine ground.

In any case, an engine-to-frame ground strap must be run from the cylinder head grounding stud to the frame and negative battery post.

Cylinder Head-To-Battery (-) Ground

Alternate Cylinder Head-To-Battery (-) Ground

The cylinder head must have a wire ground to battery as shown in the above illustrations.

Ground wires/straps should be combined at ground studs dedicated for ground use only. At "Every 12,500 miles (20 125 km) or 250 hours," Inspect/Check all engine grounds. All grounds should be tight and free of corrosion.

All ground paths must be capable of carrying any conceivable fault currents, and an awg # 0 or larger wire is recommended for the cylinder head grounding strap.

The engine alternator should be battery (-) grounded with a wire size adequate to handle full alternator charging current.

The engine has several input components which are electronic. These components require an operating voltage.

Unlike many electronic systems of the past, this engine is tolerant to common external sources of electrical noise, but electro-mechanical buzzers can cause disruptions in the power supply. If electro-mechanical buzzers are used anywhere on the vehicle, it is desirable to have the engine electronics (control group, throttle position sensor, and "check engine" lamp) powered directly from the battery system through a dedicated relay, and not through a common power bus with other key switch activated devices.

Engine Electrical System

The electrical system can have 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 through the ammeter. The starting circuit is not connected through the ammeter.

Charging System Components

Alternator

The alternator is driven by a poly-vee type belt 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) for the alternator to make the needed voltage output.

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

Starting System Components

Solenoid

Typical Solenoid Schematic

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.

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 winding, 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 to start running.

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

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