General Information

NOTE: For Specifications with illustrations, make reference to Specifications For 3100 HEUI Diesel Truck Engine. If the Specifications 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.

The 3100 HEUI engines are in-line six cylinder arrangements, with a firing order of 1, 5, 3, 6, 2, 4,. The engine rotation is counterclockwise as viewed from the flywheel. The engines series are turbocharged and air-to-air aftercooled. The 3100 HEUI engines have a bore size of 105 mm (4.1 in) and a stroke of 127 mm (5.0 in) in a displacement of 6.6 liters (403 cubic inches) or a bore size of 110 mm (4.3 in) and a stroke of 127 mm (5.0 in) in a displacement of 7.25 liters (442 cubic inches).

The hydraulic electronic unit injector system eliminates many of the mechanical components of a "pump-and-line" system. It also provides increased control of timing and fuel/air ratio. Timing advance is achieved by precise control of unit 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. An electronic 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 3100 HEUI Diesel Truck Engine's ECM will automatically provide the correct amount of fuel to start the engine. DO NOT HOLD THE THROTTLE DOWN while cranking the engine. If the engine fails to start in twenty seconds, release the starter switch. Allow the starter motor to cool for two minutes before using it again.

Cold Mode Operation

If the sum of coolant temperature and inlet air temperature is less than 35°C (95°F), the ECM will set cold start conditions; low idle rpm will be increased to 1000 rpm, and engine power will be limited. Cold mode will be de-activated when the above temperature condition is met, or after twelve minutes of running. It can also be disabled by depressing the service brake or by placing an automatic transmission in gear from neutral/park. Cold mode may ramp slowly back to 1000 rpm after disabling, if the temperature conditions still exist (and an automatic transmission is not in gear). Cold Mode also varies fuel injection amount and timing for white smoke control. The time needed for the engine to reach the normal operating temperature is usually less than the time taken for a walk-around-inspection of the vehicle.

Cold mode idle speed is disabled by depressing the service brake, throttle, or clutch (where applicable). The engine will idle at the programmed low idle value to allow it to be put in gear.

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.

Glossary Of 3100 HEUI Diesel Truck Engine Electronic Control Terms

After Market Device

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

Air Inlet Temperature Sensor

A sensor that measures the inlet air temperatures and provides a signal to the electronic control module (ECM).

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.

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 timing and is an electronic adjustment of a sensor signal.

Coolant Temperature Sensor

This sensor detects the engine coolant temperature for Cold Mode operation and Caterpillar Engine Monitoring (if Engine Monitoring is not programmed OFF)

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 electronic 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".

Diagnostic Code

Sometimes referred to as a "fault code", it is an indication of a problem or event in the electrical engine systems.

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. Generically, refers to the time ON vs. time OFF of any signal, device, or engine.

Electronic Control Module (ECM)

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

Electronic Engine Control

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

Electronic Service Tool

A Caterpillar electronic service tool used for diagnosing and programming a variety of electronic controls.

Engine Speed/Timing Sensor

Provides electrical signals to the ECM, which the ECM interprets as crankshaft position and engine speed.

Estimated Dynamic Timing

The ECM's estimate of actual injection timing.

Exhaust Brake Enable Signal

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

Failure Mode Identifier (FMI)

Type of failure the component experienced (adopted from SAE standard practice J1587 diagnostics).

Flash Memory

See Personality Module.

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. See item "Electronic Control Signal Flow Chart".

Harness

The wiring bundle connecting all components of the electrical engine systems.

Hertz (Hz)

Measure of frequency in cycles per second.

High Pressure Oil Manifold

An oil gallery added to the air intake manifold to supply the unit injectors with high pressure oil.

High Pressure Oil Pump

A gear-driven axial piston pump used to raise the engine oil pressure level from typical engine operating oil pressure level to the actuation pressure level required by the unit injectors.

Hydraulic Electronic Unit Injector (HEUI) System

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

Injection Actuation Pressure Control Valve (IAPCV)

A variable valve used to maintain proper oil pressure in the high pressure oil manifold. It is controlled by the ECM.

Injection Actuation Pressure Sensor

A sensor which measures hydraulic oil pressure and sends a signal to the ECM.

Jumper Tube

Tube assemblies used to connect the high pressure oil manifold to each Hydraulic Electronic Unit Injector.

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.

Parameter Identifier (PID)

Two or three digit code which is assigned to each component to identify data via data link to ECM.

Password

A group of numeric or alpha-numeric characters, designed to restrict access to parameters. The electrical engine systems 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

The module in the ECM which contains all the instructions (software) for the ECM and performance maps for a specific horsepower family. Software updates and re-rates are accomplished by electronically "flashing" in new data using an electronic service tool.

Power Take Off (PTO)

Operated with the cruise control switches or dedicated PTO inputs, this mode permits setting constant engine rpm when the vehicle is not moving (like a manual throttle control cable), or moving at slow speeds.

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.

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 cycle"). A PWM signal is generated by the Throttle Position Sensor.

Example of Pulse Width Modulation Signals

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.

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 for a particular application (such as truck, marine, industrial, etc.).

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 engine system that relates to a particular function, for instance: vehicle speed subsystem, etc.

Supply Voltage

A voltage is 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. May also be used as part of a PTO control.

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 in the ECM.

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 (left side view)
(1) Injection actuation pressure control valve. (2) Injection actuation pressure sensor. (3) Timing calibration connector J24/P24. (4) Wiring harness. (5) High pressure oil pump. (6) ECM. (7) Top engine speed/timing sensor. (8) Bottom engine speed/timing sensor. (9) J1/P1 Connector (OEM). (10) J2/P2 Connector (engine).

Electronic Control System Components (top view)
(1) Injection Actuation Pressure Control Valve. (2) Injection actuation pressure sensor. (3) Timing calibration connector J24/P24. (4) Wiring harness. (5) High pressure oil pump. (6) ECM. (11) Coolant Temperature Sensor. (12) Coolant temperature sensor connector J10/P10. (13) Air inlet heater lamp connector J40. (14) Air inlet heater relay connector J37/P37. (15) Air inlet heater relay. (16) Intake manifold air temperature sensor. (17) Boost pressure sensor. (18) Intake manifold air temperature sensor connector J21/P21. (19) Fuel transfer pump.

Electronic Control System Components (front view)
(2) Injection actuation pressure sensor. (16) Intake manifold air temperature sensor. (17) Boost pressure sensor.

The electronic control system is integrally designed into the engines fuel, air inlet, and exhaust systems 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 unit injector firing time, and engine rpm is controlled by adjusting the injection 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, Hydraulic Electronic 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, frequency, or pulse width in response to change in some specific system of the vehicle (examples are: speed/timing sensor, coolant temperature sensor, cruise control 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.

3100 HEUI Diesel Truck Engine Electrical Connectors And Functions

PID-FMI Flash Codes

Fuel System

Fuel System Schematic
(AA) High pressure oil line. (BB) Unit injector wiring harness. (CC) Low pressure oil supply line. (DD) Fuel line. (EE) Low pressure oil return line. (1) High pressure oil manifold. (2) High pressure oil line. (3) Hydraulic electronic unit injector. (4) Unit injector wiring harness. (5) Electronic control module (ECM). (6) Fuel pressure regulator. (7) Fuel filter. (8) Fuel transfer pump. (9) Fuel return line. (10) Injection actuation pressure control valve (IAPCV). (11) Electrical signal from ECM to IAPCV (controls oil manifold pressure). (12) Oil cooler. (13) Secondary oil filter. (14) Low pressure oil supply line. (15) High pressure oil pump. (16) Fuel line. (17) Fuel tank. (18) Low pressure oil return line. (19) Oil sump. (20) Oil pump (engine lubrication).

Fuel System Components
(1) High pressure oil manifold. (5) ECM. (7) Fuel filter. (8) Fuel transfer pump. (10) Injection actuation pressure control valve. (15) High pressure oil pump. (21) Injection actuation pressure sensor.

The 3100 HEUI fuel system uses Hydraulic Electronic Unit Injectors (3). Hydraulic Electronic Unit Injectors (3) use high pressure oil instead of using a separate cam lobe to pressurize the unit injector.

The fuel supply circuit is a conventional design for unit injected engines, in that it uses a single piston type fuel transfer pump (8) which circulates fuel at low pressure, first through the fuel filter (7) and then into the cylinder head fuel passages at low pressure. Fuel is delivered at high pressure into the combustion chamber through hydraulic electronic unit injectors (3). The unit injectors are located near the center of the combustion chambers in the cylinder head between the rocker arms.

Fuel drawn from fuel tank (7) by the fuel transfer pump (8) is typically passed through an OEM installed primary filter of approximately thirty micron rating. Some OEMs may install a combination filter/water separator. The fuel transfer pump (8) incorporates a check valve to permit fuel flow for hand priming and a pressure regulating valve to protect the system from extreme pressure.

From the fuel transfer pump (8), fuel passes through a secondary fuel filter (7) of two micron rating, and then to the fuel manifold fitting at the front of the engine.

Fuel flows continuously around each unit injector through an internal passage running the length of the head, exiting at the rear of the engine through a pressure regulator to return to the fuel tank (17). Excess fuel not being used for injection helps to cool the unit injectors and to purge air from the system. During normal under load operating conditions, fuel pressure is maintained in the range of 400 kPa (58 psi) to 525 kPa (76 psi) by an orificed pressure regulating valve at the rear of the cylinder head, which also contains a check valve and serves as a siphon break. Fuel pressure at low idle should be a minimum of 500 kPa (73 psi).

When the ECM (5) activates each unit injector the engine oil in the high pressure oil manifold (1) acts on a piston in the upper part of the unit injector. This piston has an area roughly six times the area of the unit injector plunger. Fuel is injected into the cylinder at 138 000+ kPa (20 000+ psi).

The ECM (5) is located at the rear on the left side of the engine. The system provides total electronic control of the start and duration of the fuel injection. The ECM (5) uses engine data gathered by several sensors to make adjustments on fuel delivery based on the programmed performance map used in the engine control software.

The high pressure oil pump (15) is located at the left front corner of the engine. The high pressure oil pump (15) is a gear-driven axial piston pump. It raises the engine oil pressure level from typical engine operating oil pressure level to the actuation pressure level required by the unit injectors.

The injection actuation pressure control valve (10) is located in the high pressure oil pump (15) at the top left of the engine. Operational maps stored in the module's memory identify the optimum oil pressure for the best performance.

Electronic Control System

3100 HEUI Electronic Control System

Electronic Controls

The 3100 HEUI Diesel Truck Engines 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/unit injectors to "act") to control the engine. Neither one can do anything by itself.

The Throttle Position Sensor (TPS) in the truck cab is operated by the driver to accelerate the engine. The signal from the TPS is Pulse Width Modulated (PWM) (see Glossary), and its directed first to the Power Take-Off (PTO) interlock circuit. If the remote PTO is being operated, the interlock prevents the driver in the cab from overriding the remote PTO throttle signal. This protects a pump or other PTO operated device from being over sped. The throttle signal then goes through the throttle/cruise/PTO logic and control circuits, where it is compared with other inputs; vehicle speed, engine rpm and customer parameters.

The signal then goes into the engine control logic circuits. Inputs from the coolant temperature sensor and inlet air temperature sensor are sampled, and if appropriate, the ECM will place the engine in cold mode operation. The output signal is "desired rpm", which is then routed to the electronic governor circuits.

The PTO application may be operated from a dedicated set of PTO switches in the truck cab, from PTO switches in a remote location, or by a remote PTO on-off switch with a separate throttle position sensor for variable engine speed. The software distinguishes between idle and PTO conditions. There are new parameters available for PTO/vocational applications, such as cement mixers, refuse packers and bulk haulers.

Fuel Injection

Inputs from the inlet air temperature sensor, the boost pressure sensor, and engine rpm are compared with the Fuel Ratio Control (FRC) maps. The output of this circuit is the FRC fuel position, which acts to limit fueling during acceleration until boost pressure rises, to prevent over fueling and black smoke. Once sufficient boost pressure and airflow is attained, the FRC limit on fuel position is normally higher than the desired fuel position and does not affect engine performance.

The software in the personality module contains torque maps, which establish the maximum fuel rates and therefore the power levels at all operating rpms, and set the rated fuel position. The torque maps are established by engine rating software which has been "flashed" into the personality module. In the HEUI ECM, the personality module is permanently wired in place as a part of the ECM, and cannot be physically removed and replaced. Updated software and re-rates must be "flashed" via an electronic service tool. Engine rpm and PTO customer parameters (PTO torque limits) are inputs to the torque maps. These parameters may limit torque during PTO operation as a protection for the driven device.

The electronic governor accepts the signals from torque maps, FRC fuel position, and desired rpm, and sends the fuel position signal to the fuel injection control circuits. Other inputs to fuel injection control are the position of Top Center (TC) for #1 cylinder, and engine rpm, both coming from the speed/timing signal logic circuit.

TC for #1 cylinder is established by signals from the dual speed/timing sensors. These are passive sensors mounted on the upper left side of the engine (behind the air compressor) so as to pick up the magnetic impulses from a series of twenty-five teeth on the back of the camshaft gear. Twenty-four of these teeth are evenly spaced 15 degrees apart, while the twenty-fifth is placed 22 1/2 degrees after TC of #1 cylinder. This allows the ECM to establish the position of #1 cylinder, and fire each unit injector at the correct time and in firing order. The speed/timing sensors are redundant which permits the operator to continue without down time (if either one fails, the engine will remain running). However, an active fault code will be present, and service should be obtained as soon as possible. The sensors must be replaced as a set, as they are NOT identical electrically.

The output of the fuel injection control circuits is a shaped pulse of 110 volts DC which energizes the unit injector solenoid. The solenoid is fast-acting, and allows high-pressure oil to enter the unit injector and act upon an intensifier piston, which multiplies the hydraulic force to several times the input oil pressure. This pressurizes the fuel plunger, causing the nozzle to open. The length of the electrical pulse determines how long fuel will flow and the hydraulic pressure determines the rate of flow. The HEUI unit injector therefore permits flexibility of fuel start, fuel stop, and rate of flow, independent of the limitations of a cam profile.

Unit Injector Hydraulic Oil Supply

Unit Injector Hydraulic Oil Supply
(1) "Jumper" tube. (2) Hydraulic electronic unit injector. (3) High pressure oil manifold.

The high pressure oil pump is a gear-driven axial piston pump. It raises the engine oil pressure level from typical engine operating oil pressure level to the actuation pressure level required by the unit injectors. This high pressure oil flows through lines into the high pressure oil manifold (3) located near the hydraulic electronic unit injectors (2). The manifold stores the oil at actuation pressure ready for unit injector operation. Oil is distributed equally and continually to the top of all unit injectors through "jumper" tubes (1) under the valve cover. After pressurizing a unit injector, the oil is discharged from the unit injectors onto the cylinder head, where it drains back to the oil pan. No oil return lines are required.

HEUI uses a high-pressure hydraulic system. The oil for this system is drawn from the engine lubrication system on the left side of the block and raised to high pressure by a gear-driven pump. The pressure is regulated by the ECM to the optimum pressure for a given set of conditions as determined by operational maps stored in memory. Available pressure ranges from approximately 5 MPa (725 psi) to 23 MPa (3335 psi). This is a closed-loop system; the ECM senses hydraulic pressure from the injection actuation pressure sensor on the high pressure oil manifold, and regulates pressure via a signal from the ECM to the injection actuation control valve mounted on the high pressure hydraulic pump.

High pressure oil is routed from the pump output through a steel tube to the oil manifold on the inlet manifold. oil is allowed to dump inside of the inlet manifold base and return to the oil sump. There are no return oil lines.

Hydraulic Electronic Unit Injector

Hydraulic Electronic Unit Injector
(1) Poppet valve. (2) Lower seat (poppet valve). (3) Entry port (high pressure oil). (4) Solenoid return spring. (5) Solenoid. (6) Upper seat (poppet valve). (7) Plunger. (8) Intensifier piston. (9) Poppet cavity (oil). (10) Check ball (spring loaded). (11) Barrel. (12) Piston cavity (fuel). (13) Check ball (fuel inlet). (14) Reverse flow check. (15) Fill port(s) (Fuel). (16) Nozzle assembly. (17) Nozzle valve.

The injection pump, fuel lines and nozzles used in traditional Caterpillar Diesel Engines have been replaced with a hydraulic electronic unit injector for each cylinder. A solenoid (5) on each unit injector controls the amount of fuel delivered by the unit injector. An Electronic Control Module (ECM) sends a signal to each unit injector solenoid (5).

Low pressure fuel from the fuel supply manifold (through drilled passages in the cylinder head) enters the hydraulic electronic unit injector at the fill port(s) (15). Fuel can be injected at any time depending on the start of injection timing requirements programmed into the electronic control module.

A 110 volt DC electrical pulse from the fuel injection control circuits in the ECM energizes the solenoid (5) in the unit injector. The duration of this pulse determines the length of time that fuel is allowed to flow through the nozzle valve (17). The hydraulic oil pressure on the intensifier piston (8) determines injection pressure. The duration is determined from inputs to the ECM/Personality Module; rpm demand from the throttle position sensor or cruise control or PTO, power demand as determined by the electronic governor according to the load, and power/torque limitations as established by the rating limits, customer parameters, and AFRC circuits.

When the engine is in an "at rest" condition, the solenoid (5) is not energized, and the poppet valve (1) is held on its lower seat (2) by the solenoid return spring (4). In this "at rest" condition, high pressure inlet oil is blocked and the poppet cavity (9) is opened to drain. The intensifier piston (8) and the plunger (7) are at the top of their bore and the piston cavity (12) is full.

Unit injector oil flow
(2) Lower seat (poppet valve). (6) Upper seat (poppet valve).

When a pulse energizes the solenoid (5), the poppet valve (1) moves off the lower seat (2) and onto the upper seat (6). The path to the poppet cavity (9) is closed. High pressure oil enters the unit injector thru entry port (3) and acts on the top of the intensifier piston (8). Pressure builds, pushing the plunger (7) down. The downward movement of the plunger (7) pressurizes the fuel in the piston cavity (12), causing the nozzle valve (18) to open. The downward stroke of the piston during injection creates a positive pressure which moves intensifier piston (8) and plunger (7) downward, pressure increases on the fuel in the cavity of barrel (11) below plunger (7). Fuel flows past reverse flow check (14) down the fuel passage and pressurizes the nozzle. When valve opening pressure (VOP) is reached nozzle valve (17) opens and injection begins.

The intensifier piston (8) continues to move downward until the solenoid (5) is de-energized. The de-energized solenoid (5) permits the poppet valve (1), intensifier piston (8), and plunger (7) to return to its "at rest" condition. As the plunger (7) returns, it draws fuel into the piston cavity (12) through the fill port(s) (15) across a fuel inlet check ball (13). The unit injector is now ready to repeat the cycle.

The nozzle assembly (16) is of conventional design with the exception of the fuel inlet check ball (13) and reverse flow check (14). The fuel inlet check ball (13) unseats and seals during the downward stroke of the plunger (7) to allow the piston cavity (12) to refill. The reverse flow check (14) is a one way check plate which allows fuel to enter the nozzle assembly (16), but closes to prevent reverse flow at the end of injection. It traps fuel pressure in the nozzle to prevent combustion gas from entering the nozzle if there is leakage at the nozzle valve seat.

Fuel Heater And Water Separator (If Equipped)

(1) Fuel inlet. (2) Fuel filter. (3) Fuel outlet. (4) Base. (5) Heater. (6) Temperature sensor. (7) Drain valve.

Some engines may have a combination fuel heater and water separator. The fuel heater is controlled by a thermostat located in the base of the unit. The thermostat is preset to turn the heater ON when the fuel temperature is below 2°C (35°F) and OFF when the fuel temperature is 7°C (45°F).

Water that has been separated from the fuel can be drained from the unit by lifting up on the drain valve (7).

Air Inlet And Exhaust System

Air Flow Schematic
(1) Air line. (2) Aftercooler core. (3) Inlet manifold. (4) Exhaust outlet from turbocharger. (5) Turbine side of turbocharger. (6) Compressor side of turbocharger.

The components of the air inlet and exhaust system control the quality and the amount of air available for combustion. These components are the air cleaner, turbocharger, aftercooler, cylinder head, valves and valve system components, piston and cylinder, and exhaust manifold.

Inlet air is pulled through the air cleaner, compressed and heated by the compressor wheel in compressor side of turbocharger (6) to about 150°C (300°F), then pushed through the air-to-air aftercooler core (2) and moved to the air inlet manifold (3) at about 43°C (110°F). Cooling of the inlet air increases combustion efficiency, which helps to lower fuel consumption and increase horsepower output. Aftercooler core (2) is a separate cooler core installed in front of the standard engine radiator core of the truck. Ambient temperature air is moved across the aftercooler core by the engine fan and by the ram effect of the vehicles forward motion, this cools the turbocharged inlet air.

From the aftercooler core (2) the air is forced into the cylinder head to fill the inlet ports. Air flow from the inlet port into the cylinder is controlled by the intake valves.

Air Inlet And Exhaust System
(2) Aftercooler core. (4) Exhaust outlet. (5) Turbine side of turbocharger. (6) Compressor side of turbocharger. (7) Exhaust manifold. (8) Exhaust valve. (9) Intake valve. (10) Air inlet.

There are two intake and two exhaust valves for each cylinder. Intake valves open when the piston moves down on the inlet stroke. When the intake valves open, cooled compressed air from the inlet port 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. 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. When the piston moves up again, it is on the exhaust stroke. The exhaust valves open, and the exhaust gases are pushed through the exhaust port into the exhaust manifold. After the piston makes the exhaust stroke, the exhaust valves close and the cycle (inlet, compression, power, exhaust) starts again.

Exhaust gases from exhaust manifold (7) enter turbine side of the turbocharger (5) and cause the turbine wheel to turn. The turbine wheel is connected to the shaft which drives the compressor wheel. Exhaust gases from the turbocharger pass through the exhaust outlet pipe, the muffler and the exhaust stack.

Turbocharger

Turbocharger
(1) Air inlet. (2) Compressor housing. (3) Compressor wheel. (4) Bearing. (5) Oil Inlet port. (6) Bearing. (7) Turbine housing. (8) Turbine wheel. (9) Exhaust outlet. (10) Oil outlet port. (11) Exhaust inlet.

The turbocharger is installed on the center section of the exhaust manifold. All the exhaust gases from the engine go through the turbocharger. The compressor side of the turbocharger is connected to the aftercooler by pipe.

The exhaust gases go into turbine housing (7) through exhaust inlet (11) and push the blades of turbine wheel (8). The turbine wheel is connected by a shaft to compressor wheel (3).

Clean air from the air cleaners is pulled through the compressor housing air inlet (1) by the rotation of compressor wheel (3). 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, 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 cylinders. 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.

Wastegate Turbocharger
(12) Actuating lever. (13) Canister. (14) Line (boost pressure).

When the engine is operating under low boost conditions a spring pushes against a diaphragm in canister (13) and moves actuating lever (12) to close the wastegate valve which will allow the turbocharger to operate at maximum performance.

As the boost pressure increases against the diaphragm in canister (13), the wastegate valve is opened and the rpm of the turbocharger is limited by bypassing a portion of the exhaust gases thru a line (14) around the turbine wheel of the turbocharger.

NOTE: The wastegate turbocharger is preset at the factory and no adjustment can be made.

Bearings (4 and 6) for the turbocharger use engine oil under pressure for lubrication. The oil comes in through the oil inlet port (5) and does through passages in the center section for lubrication of the bearings. Oil from the turbocharger goes out through the oil outlet port (10) in the bottom of the center section and goes back to the engine lubrication system.

Valve System Components

Valve System Components
(1) Rocker arm. (2) Spring. (3) Valve. (4) Push rod. (5) Lifter. (6) Camshaft lobe.

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

The crankshaft gear drives the camshaft gear through an idler. The camshaft must be timed to the crankshaft to get the correct relation between piston and valve movement.

The camshaft has two cam lobes for each cylinder. The lobes operate the intake and exhaust valves. As the camshaft turns, lobes on the camshaft cause the lifters (5) to move push rods (4) up and down. Upward movement of the push rods against rocker arms (1) results in downward movement (opening) of valves (3).

Each cylinder has one intake and one exhaust valve. Valve springs (2) close the valves when the lifters move down.

Inlet Air Heater

To aid starting and prevent white smoke emission at start up, the engines are equipped with an electric heater located at the air inlet casting. Under the proper conditions of jacket water temperature, intake manifold temperature, ignition position, and elapsed time, the electronic control module turns the heater system on. The system is capable of delivering heat for thirty seconds prior to start up, during cranking, and up to seven minutes continuous and thirteen minutes of cycling (ten seconds on, ten seconds off) after the engine has started.

If for any reason the inlet air heater system malfunctions, the engine will still start and run. The only concerns may be the amount of "white smoke" present and the possible need to use an alternative starting aid.

System Components

The basic components of the inlet air heater system are: inlet air heater relay, heater element, coolant temperature sensor, intake manifold air temperature sensor, electronic control module, and an indicator lamp.

Location Of Components
(1) Inlet air heater relay. (2) Ground strap (from heater group to the engine). (3) Inlet manifold. (4) Inlet air heater.

Location Of Components
(1) Inlet air heater relay. (5) Coolant temperature sensor.

The inlet air heater relay (1) is located on the inlet manifold cover. It turns the 12 V heater ON and OFF in response to signals from the ECM.

The inlet air heater relay (1) is located between the inlet manifold and the air inlet elbow. The heater element has a ground strap (2) that must be connected to the engine.

There are four conditions that would cause the inlet air heater to be activated.

1. Power up. Regardless of temperature, the heater and heater lamp should come on for two seconds when the ECM is first powered up (lamp check).

2. Preheat mode. When the sum of coolant temperature plus inlet air temperature is less than 25°C (77°F), the ECM will turn the heater and lamp ON for 30 seconds as a preheat cycle, then OFF. If the operator attempts to start the engine before preheat has timed out, the ECM goes to the cranking mode for heater control.

3. Cranking mode. When the engine is cranking, the ECM will turn the heater ON if the sum of coolant temperature and inlet manifold temperature is less than 25°C (77°F). The heater will remain ON while cranking. If the engine fails to start, the ECM reverts to preheat mode and will activate the heater for another 30 seconds.

4. Engine running cycle. After the engine has started, the same combination of inlet air temperature and coolant temperature will determine if the heater remains activated. The engine running cycle has two segments. Continuous mode. The heater remains on steadily for a maximum of 7 minutes after starting. If the same conditions exist, the ECM will shift to on-off mode. The heater is cycled continuously, ON for 10 seconds and OFF for 10 seconds, for a maximum time of 13 minutes, after which the heater is shut off.

Operation when one of the temperature sensors have failed.

1. When the coolant temperature sensor has an open or short circuit, the heater will be activated if inlet air temperature is less than 10°C (50°F).

2. When the inlet manifold air temperature sensor has an open or short circuit, the heater will be activated if coolant temperature is less than 40°C (104°F).

Reactivate heater. When the engine has been warm and is cooling down, if an engine start is attempted, the inlet air heater will be reactivated if the sum of coolant temperature and inlet air temperature has dropped below 25°C (77°F).

If the sum of coolant temperature and inlet air temperature never reaches 35°C (95°F) during the timed 20 minute period, the heater will be turned OFF at the end of the 20 minute period.

Inlet Air Heater Schematic (Typical Example)
(1) Inlet air heater. (2) Inlet air heater relay. (3) Battery. (4) Inlet air heater lamp. (5) Fuse panel. (6) Electronic control module.

Inlet Air Heater Controller Functional Flow Chart

Lubrication System

Lubrication System Schematic
(1) Hydraulic pump. (2) High pressure relief valve. (3) Passage (to rocker arms). (4) Jumper tube. (5) High pressure oil line. (6) Injection actuation pressure control valve. (7) High pressure oil manifold. (8) Hydraulic pump oil supply line. (9) Piston cooling jets. (10) Cylinder head gallery. (11) Passage (to push rod lifters mounted in the side covers). (12) Main bearings. (13) Camshaft bearing. (14) Passage (to the oil pan). (15) Main oil gallery. (16) Turbocharger oil supply line. (17) Passage (to front housing). (18) Passage (to oil pump idler gear bearing). (19) Oil filter bypass valve. (20) Passage (to camshaft idler gear bearing). (21) Passage. (22) Oil filter. (23) Oil cooler bypass valve. (24) Oil cooler. (25) Oil pump. (26) Oil pump bypass valve. (27) Oil pan.

Oil pump (25) is mounted to the bottom of the cylinder block inside the oil pan (28). The oil pump (25) pulls oil from oil pan (28) and pushes the oil through passage to oil cooler (24). Oil then flows through oil filter (22). The filtered oil then enters the turbocharger oil supply line (16) and main oil gallery (15).

Engine Right Side
(16) Turbocharger oil supply line. (19) Oil filter bypass valve. (22) Oil filter. (23) Oil cooler bypass valve. (24) Oil cooler. (29) Turbocharger oil return line.

Engine Left Side
(1) Hydraulic pump. (7) High pressure oil manifold. (5) High pressure oil supply line. (8) Hydraulic pump oil supply line.

The main oil gallery (15) distributes oil to main bearings (12), piston cooling jets (9) and camshaft bearing (13). Oil from main oil gallery (15) also exits the front of the block and enters a groove cast in the front housing.

Oil enters the crankshaft through holes in the bearing surfaces (journals) for the main bearing (12). Passages connect the bearing surface (journal) for the main bearing (12) with the bearing surface (journal) for the connecting rod.

The front housing passage sends the oil flow in two directions. At the upper end of the passage, oil is directed back into the block and up to cylinder head gallery (10) thru passage (3) to the rocker arm mechanism. A passage (18) sends oil to the oil pump idler gear bearing.

Oil from the front main bearing enters a passage (20) to the camshaft idler gear bearing (20). Oil passages in the crankshaft send oil from all the main bearing (12) thru the connecting rods to the connecting rod bearings.

The passages send oil from the camshaft bearing (13) to an oil passage in the side covers. The oil then enters a hole in the shafts to push rod lifters (11) to lubricate the lifter roller bearings.

NOTE: Engines equipped with an auxiliary oil filter (27) will pick up oil at a port and the filtered oil will be returned to oil pan (28).

The hydraulic pump (1) is a gear-driven axial piston pump. It raises the engine oil pressure level from typical engine operating oil pressure to the actuation pressure level required by the unit injectors. The injection actuation pressure control valve (6) electronically controls the output pressure of the hydraulic pump (1).

The oil circuit consists of a low pressure section and a high pressure section. The low pressure circuit typically operates at a pressure of 240 to 480 kPa (35 to 70 psi). Its function is to provide filtered engine oil to the hydraulic pump (1) as well as the lubricating system of the engine. Oil is drawn from the engine oil pan (28) and supplied through the oil cooler (24) and oil filter (22) to both the engine and the hydraulic pump (1).

The high pressure oil circuit provides actuation oil to the unit injector and operates in a pressure range typically between 4 and 23 MPa (581 and 3338 psi). This high pressure oil flows through lines into a high pressure oil manifold (7) located on the left side of the air inlet manifold. The manifold stores the oil at actuation pressure ready for unit injector operation. Oil is discharged from the unit injector under the valve cover so that no return lines are required.

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

The oil pump bypass valve (26) limits the pressure of the oil coming from the oil pump (25). The oil pump (25) can put more oil into the system than is needed. When there is more oil than needed, the oil pressure increases and the oil pump bypass valve (26) will open. This allows the oil that is not needed to go back to the suction side of the oil pump (25).

With the engine cold (starting conditions), bypass valves (19 and 23) will open and give immediate lubrication to all components when cold oil with high viscosity causes a restriction to the oil flow through oil cooler (24) and oil filter (22). The oil pump (25) sends the cold oil through the bypass valves around the oil cooler (24) and oil filter (22) to the turbocharger oil supply line (16) and the main oil gallery (15) in the cylinder block.

When the oil gets warm, the pressure difference in the bypass valves decreases and the bypass valves close. Now there is a normal flow of oil through the oil cooler and oil filter.

The bypass valves will also open when there is a restriction in the oil cooler (24) or oil filter (22). This action does not let oil cooler (24) or oil filter (22) 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 (15) in the cylinder block. From here the piston cooling jets (9), valve mechanism, camshaft bearing (13), crankshaft main bearings, and the turbocharger cartridge are lubricated.

An oil cooling chamber is formed by the lip forged 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 oil pan (28) 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
(29) Breather. (30) Hose. (31) Cylinder head.

Breather (29) allows blowby gases from the cylinders during engine operation to escape from the crankcase. The blowby gases flow or discharge through hose (30) into the atmosphere. This prevents pressure from building up that could cause seals or gaskets to leak.

Hydraulic Oil (Injection Actuation Pressure Control Valve)

(1) Fuel pump. (2) Injection actuation pressure control valve (IAPCV). (3) Oil accumulator. (4) Gear. (5) High pressure oil pump.

The Injection Actuation Pressure Control Valve (IAPCV) is an electronically operated control valve which closely controls the hydraulic pump output pressure by bypassing excess flow to the return circuit. A variable signal current from the ECM to the IAPCV determines pump output pressure. The IAPCV (2) is located on the front right side of the engine and is connected to the high pressure oil pump (5).

Cooling System

This engine has a pressure type cooling system with a shunt line.

A pressure type cooling system gives two advantages. The first advantage is that the cooling system can have a safe operation at a temperature that is higher than the normal boiling (steam) point of water. The second advantage is that this type of system prevents cavitation (the sudden making of low pressure bubbles in liquids by mechanical forces) in the water pump. With a pressure system, it is more difficult for an air or steam pocket to be made in the cooling system.

The shunt line keeps the water pump from cavitation, by providing a constant flow of coolant to the water pump.

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.

Cooling System Schematic
(1) Cylinder head. (2) Water temperature regulator housing. (3) Expansion tank. (4) Shunt line (expansion tank to water pump). (5) Bypass hose. (6) Radiator. (7) Cylinder block. (8) Oil cooler. (9) Water pump.

Water pump (9) is located on the right side of the cylinder block. It is belt driven from the crankshaft pulley. Coolant can enter the water pump three ways: through the bottom inlet of the water pump, through bypass hose (5) into the top of the water pump, or through shunt line (4) into the top of the water pump.

Coolant from the bottom of the radiator is pulled into the bottom inlet of the pump by impeller rotation. The coolant exits the back of the pump directly into the oil cooler cavity of the block.

All the coolant passes through the core of the oil cooler and enters the internal water manifold of the cylinder block. The manifold distributes the coolant to water jackets around the cylinder walls.

Water Lines Group
(1) Cylinder head. (2) Water temperature regulator housing. (5) Bypass hose. (10) Outlet (to radiator). (11) Water temperature regulator. (12) Air vent valve (located in flange of thermostat). (13) Water return from air compressor (if equipped). (14) Water temperature sensor. (15) Heater supply and return ports (located on the back side of housing).

From the cylinder block, the coolant flows into passages in the cylinder head. The passages send the flow around the unit injector sleeves and inlet and exhaust passages. The coolant now enters water temperature regulator housing (2) at the front right side of the cylinder head.

Water temperature regulator (11) controls the direction of flow. If the coolant temperature is less than normal, the water temperature regulator is closed. The coolant is directed through bypass hose (5) and into the top inlet of the water pump. When the coolant gets to the correct temperature, water temperature regulator (11) opens, and closes the bypass going to the pump. Most of the coolant goes through outlet (10) to the radiator for cooling. The remainder flows through bypass hose (5) and into the water pump.

The shunt line (4) runs from the top of the water pump to an expansion tank. This line must be routed to avoid trapping any air. By providing a constant flow of coolant available to the water pump, the shunt line keeps the water pump from cavitation.

NOTE: Water temperature regulator (11) is an important part of the cooling system. It divides coolant flow between the radiator and the bypass as necessary to maintain the correct temperature. If the water temperature regulator is not installed in the system, there is no mechanical control, and most of the coolant will take the path of least resistance through the bypass. This will cause the engine to overheat in hot weather. In cold weather, even the small amount of coolant that goes through the radiator is too much, and the engine will not get to normal operating temperatures.

NOTE: Air vent valve (12) will allow the air to escape past the water temperature regulator from the cooling system while the radiator is being filled. During normal operation the air vent valve will be closed to prevent any coolant flow past the water temperature regulator.

Coolant For Air Compressor (If Equipped)

Coolant Lines For Air Compressor
(16) Coolant supply line (17) Coolant return line (18) Air compressor.

If the engine is equipped with an air compressor, coolant is supplied from the water temperature regulator housing to air compressor (18) through coolant supply line (16) and is circulated through the air compressor and is returned to the cooling system through coolant return line (17) into the water temperature regulator housing (2).

Coolant Conditioner (If Equipped)

Some conditions of operation have been found to cause pitting (small holes in the metal surface) from corrosion or cavitation erosion (wear caused by air bubbles in the coolant) on the outer surface of the cylinder wall and the inner surface of the cylinder block next to the cylinder wall. 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, similar to the fuel filter and oil filter elements, fastens to a base that is mounted on the front of the engine. Coolant flows from the water pump through the base and element back to the block. There is a constant flow of coolant through the element when valves are in the OPEN position.

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, and they are called 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 and 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 has seven main bearings. Two bolts hold each bearing cap to the block.

Removal of the oil pan allows access to the crankshaft, main bearings caps, piston cooling jets, and oil pump.

The camshaft compartment is accessible through covers on the left side of the cylinder block. These side covers support the push rod lifters. The camshaft is supported by bearings pressed into the cylinder block. There are seven camshaft bearings.

The cylinder head is separated from the block by a steel and non-asbestos fiber gasket. Coolant flows out of the block through gasket openings and into the head. This gasket also seals the oil supply and drain passages between the block and the head. The air inlet ports are on the top of the head, while the exhaust ports are located on the right side of the head. There is one intake and one exhaust valve for each cylinder. Replaceable valve guides are pressed into the cylinder head. The hydraulically actuated electronically controlled unit injector is located between the two valves. Fuel is injected directly into the cylinders at very high pressure. A push rod and rocker arm system controls the valves.

Pistons, Rings And Connecting Rods

High output engines with high cylinder pressures require two piece articulated pistons. Refer to the parts book to obtain information about the type of pistons used in a specific engine.

The two piece articulated piston consist of an alloy forged steel crown connected to an aluminum skirt by the piston pin. The two piece articulated piston has three rings: one compression ring, an intermediate ring, and one oil ring. All the rings are located above the piston pin bore. The compression ring is of the KEYSTONE type, which have a tapered shape. The action of the ring in the piston groove, which is also tapered, helps prevent seizure of the rings caused by carbon deposits. The intermediate ring is rectangular with a sharp lower edge. The oil ring is a standard (conventional) type. Oil returns to the crankcase through holes in the oil ring groove.

Oil from the piston cooling jets spray the underside of the pistons. This lubricates and cools the pistons, and improves piston and ring life.

The connecting rod has a taper on the pin bore end. This gives the rod and piston more strength in the areas with the most load. Two bolts hold the rod cap to the rod. This design keeps the rod width to a minimum, so that the rod can be removed through the cylinder.

Crankshaft

The crankshaft changes the combustion forces in the cylinder into usable rotating torque which powers the equipment. 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 on the front of the engine. The gear group drives the oil pump, camshaft, hydraulic oil pump, and the gear driven air compressor and/or power steering pump. In addition to this, the front belt pulleys on the crankshaft drive the radiator fan, water pump, alternator and freon compressor.

Hydrodynamic seals are used at both ends of the crankshaft to control oil leakage. The hydrodynamic grooves in the seal lip move lubrication oil back into the crankcase as the crankshaft turns. The front seal is located in the front housing. The rear seal is installed in the flywheel housing.

Schematic Of Oil Passages In Crankshaft

Pressure oil is supplied to all main bearings through drilled holes in the webs of the cylinder block. The oil then flows through drilled holes in the crankshaft to provide oil to the connecting rod bearings. The crankshaft is held in place by seven main bearings. A thrust main bearing next to the rear main bearing controls the end play of the crankshaft.

Vibration Damper

The force from combustion in the cylinders will cause the crankshaft to twist. This is called torsional vibration. If the vibration is too great, the crankshaft will be damaged. The vibration damper limits the torsional vibrations to an acceptable amount to prevent damage to the crankshaft.

Rubber Damper (If Equipped)

Rubber Vibration Damper
(1) Crankshaft. (2) Ring. (3) Rubber ring. (4) Hub. (5) Alignment marks.

The hub (4) and ring (2) are isolated by a rubber ring (3). The vibration damper has alignment marks (5) on the hub and the ring. These marks give an indication of the condition of the vibration damper.

Viscous Damper (If Equipped)

Cross Section Of Vibration Damper
(1) Crankshaft. (2) Weight. (3) Case.

The vibration damper is installed on the front of crankshaft (1). The damper has a weight (2) in a case (3). The space between the weight and the case is filled with thick fluid. The weight moves in the case to limit the torsional vibration.

Camshaft

The camshaft is located in the upper left side of the block. The camshaft is driven by gears at the front of the engine. Seven bearings support the camshaft. A thrust plate is mounted between the camshaft drive gear and a shoulder of the camshaft to control the end play of the camshaft.

The camshaft is driven by an idler gear which is driven by the crankshaft gear, so the camshaft rotates in the same direction as the crankshaft (CCW as viewed from the flywheel). There are timing marks on the crankshaft gear, idler gear, and the camshaft gear to assure the correct camshaft timing to the crankshaft for proper valve operation.

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

Electrical System

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

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

If the vehicle has a disconnect switch, the starting circuit can operate only after the disconnect switch is put in the ON position.

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

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

Charging System Components

Alternator

Alternator Components (Typical Example)
(1) Brush holder. (2) Rear frame. (3) Rotor. (4) Stator. (5) Drive end frame. (6) Fan assembly. (7) Slip rings. (8) Rectifier.

The alternator has three phase, full-wave, rectified output. It is a brush type alternator.

The alternator is an electrical and mechanical component driven by a belt from engine rotation. It is used to charge the storage battery during engine operation. The alternator is cooled by a fan that is a part of the alternator. The fan pulls air through holes in the back of the alternator. The air exits the front of the alternator, cooling it in the process.

The alternator converts mechanical and magnetic energy to alternating current (AC) and voltage. This process is done by rotating a direct current (DC) electromagnetic field (rotor) inside a three phase stator. The alternating current and voltage (generated by the stator) are changed to direct current by a three phase, full wave rectifier system using six silicone rectifier diodes. The alternator also has a diode trio which is an assembly made up of three exciter diodes. The diode trio rectifies field current needed to start the charging process. Direct current flows to the alternator output terminal.

A solid state regulator is installed in the back of the alternator. Two brushes conduct current, through two slip rings, to the field coil on the rotor.

There is also a capacitor mounted in the back of the alternator. The capacitor protects the rectifier from high voltages. It also suppresses radio noise.

Regulator

The voltage regulator is a solid state (transistor, stationary parts) electronic switch which controls the alternator output. The regulator limits the alternator voltage to a preset value by controlling the field current. 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.

NOTE: Refer to Service Manual, SENR3862, for detailed service information for the Delco Remy 27 SI Series Alternator.

NOTE: For engines which have the alternator connected to an engine component, the ground strap must connect that component to the frame or to the battery ground.

Starting System Components

Starter Solenoid

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

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

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

Typical Solenoid

The solenoid switch is made of an electromagnet (one or two sets of windings) around a hollow cylinder.

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

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

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

Starter Motor

Starter Motor (Typical Example)
(1) Brush assembly. (2) Field. (3) Solenoid. (4) Clutch. (5) Pinion. (6) Armature.

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

NOTE: Some starters have starter-to-frame ground straps. But, many of these starters are not electrically grounded to the engine. They have electrical insulation systems. For this reason, the starter-to-frame ground strap may not be an acceptable engine ground. Original equipment starters are electrically grounded to the engine. They have a ground wire from the starter to the negative terminal of the battery. If a starter change is made, consult an authorized dealer for proper grounding procedures for that starter.

The starter motor has a solenoid. When the ignition switch is turned to the START position, the starter solenoid will be activated electrically. The solenoid plunger (core) will now move to push the starter pinion, by a mechanical linkage, to engage with the flywheel ring gear. 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 cannot turn the starter motor too fast.

When the ignition switch is released from the START position, the starter solenoid is deactivated (current no longer flows through the windings). The spring now pushes the plunger (core) back to the original position, and, at the same time, moves the pinion gear away from the flywheel ring gear.

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 aluminium 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 is recommended 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.

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