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 Clearance Setting

Intake ... 0.38 mm (.015 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.

Model Views/Electronic Components

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.

Several distinct design features follow:

1. Two piece articulated piston with forged steel crown and forged aluminum skirt.

2. Two piece cylinder block with cast iron crankcase and aluminum spacer block.

3. Mid supported cylinder liner with high ring travel cooling.

4. Siamese plenum intake ports.

5. Oil pump bypass valve controlled by the engine oil manifold pressure.

6. Temperature regulated oil inlet to the engine oil cooler.

7. Bypass oil filter (an attachment).

8. Helical gear fuel transfer pump.

9. Engine braking retarder available.

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 firing time. Engine rpm is controlled by adjusting the firing 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 3176 ECM will automatically provide the correct amount of fuel to start the engine. DO NOT HOLD THE THROTTLE DOWN while cranking the engine. The engine light should be ON while the engine is cranking, but should GO OUT, after the engine starts. 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

At lower temperatures [below approximately 15°C (60°F)], the engine control system performs a "cold start" strategy. This "cold start" strategy (known as "cold mode" monitors coolant temperature and will increase the idle speed to 1000 rpm, until the engine is warm enough to drive the truck. It also varies fuel injection amount and timing for maximum startup and white smoke control. Cold Mode will continue until coolant temperature exceeds 20°C (68°F). The time needed for the engine to reach the normal mode of operation is usually less than the time taken for a walkaround-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.

Three Cylinder Cut-out

Three cylinder cut-out occurs when the engine is operated above approximately 1600 rpm in low load conditions. When these conditions exist, the 3176 Engine does not inject fuel into cylinders 4, 5 and 6, in order to obtain more precise fuel metering, reduce engine vibration and extend engine life. The accompanying change in the feel and sound of the engine should not be misdiagnosed as an engine problem. When more power is needed, all six cylinders are fueled and full power is delivered.

Three cylinder cut-out can be observed using an Electronic Control Analyzer Programmer (ECAP). The Cylinder Cut-out and Injection Signal Duration screen will display the electrical injection signal duration to each cylinder in bar graph form. During three cylinder cut-out, cylinders 1, 2 and 3 will display injection signal durations, while cylinders 4, 5 and 6 will display no injection signal.

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), Personality Module, and Transducer Module. For a brief explanation of each of the customer specified parameters, see the Operation and Maintenance Manual.

Boost Pressure Sensor

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

Customer Specified Parameters

Parameters that can be changed and whose values are determined by the customer.

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.

Digital Diagnostic Tool (DDT)

A Caterpillar service tool used to program and for diagnosis of the electronic control system.

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 Control Analyzer and Programmer (ECAP)

A Caterpillar service tool used to program and for diagnosis of a variety of electronic controls.

Electronic Control Module (ECM)

The Electronic Control Module (ECM) is a microprocessor based control module which is the main control module of the electronic control system.

Retarder Enable Line

The retarder enable line interfaces the ECM to the engine retarder. This will prohibit operation of the engine brake under unsafe engine operating conditions.

Engine Speed/Timing Sensor

A sensor which generates pulses when it detects the rotating teeth on the timing reference ring mounted on the camshaft at the front of the engine. These pulses represent engine rpm and camshaft position which is used to control fuel injection timing.

Injection Timing Control

The use of electronically controlled unit injectors provides total electronic control of the fuel injection timing.

Parameter

Any of a set of physical properties whose values determine the characteristics of behavior of the engine and/or vehicle in which the engine is installed.

Personality Module

Mounted directly to the ECM, this module contains the operating program and performance maps.

Transducer Module

The transducer module is mounted directly to the ECM and contains a boost pressure sensor and associated circuitry.

Pulse Width Modulation (PWM)

A digital type of electronic signal corresponding to a measured variable. The length of the pulse (or signal) is controlled by the measured variable. This variable is quantified by the ratio of the percent of time "on" divided by the percent of time "off". A PWM signal is generated by the Throttle Position Sensor, Engine Speed/Timing Sensor and ECM Retarder Enable.

Throttle Position Sensor

An electronic sensor connected to the accelerator pedal. The throttle position sensor communicates pedal position 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 Buffer

A device used to waveshape and amplify the output of the vehicle speed sensor. The vehicle speed buffer circuit provides an output for driving a speedometer as well as a logic level signal for input into the ECM.

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) Speed/timing sensor. (2) Coolant temperature sensor. (3) Injector enable circuit. (4) Fuel manifold. (5) Engine wiring harness. (6) Fuel transfer pump. (7) Fuel pressure sensor. (8) Electronic control module (ECM). (9) Personality module. (10) Transducer module. (11) Boost sensor.

Major components of the electronic control system are: (1) speed/timing sensor (in the right side of the front housing), (2) Coolant temperature sensor (located in the water temperature regulator housing), (11) Boost sensor [located in the transducer module (10)], (3) Injector enable circuit (provides signal to the fuel injection pump group solenoids), (4) Fuel manifold, (5) Engine wiring harness, (6) Fuel transfer pump, (7) Fuel pressure sensor, (8) Electronic control module (ECM), (9) Personality module, (10) Transducer module, 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.

3176 Electronic Control System

3176 Electronic Control System

The output components of the electronics will be discussed in this section. Various sensors feed engine and vehicle data to the electronic control module (ECM). The standard "package" of sensors monitor engine rpm and timing, throttle position, coolant temperature, fuel pressure, boost pressure, vehicle speed, cruise switches status (on/off and set/resume), clutch switch, brake switch, and parking switch. The ECM processes this data and sends electronic signals to the fuel injector pump solenoids. The solenoids are energized and de-energized to start and stop respectively, the fuel discharge from the fuel injection pumps. See the topic, Electronically Controlled Unit Injector, for a complete explanation of the fuel injection process.

Data Link

The engine incorporates a DATA LINK intended for communication with other microprocessor based devices that are compatible with the proposed American Trucking Association (ATA) and SAE standard. The DATA LINK follows SAE recommended practice J1708 for the hardware description and recommended practice J1587 for the data protocol.

The DATA LINK can reduce duplication of truck sensors by allowing controls to share information. The DATA LINK is used to communicate engine information to other electronic vehicle control systems and to interface with Caterpillar service tools [Electronic Control Analyzer and Programmer (ECAP) and Digital Diagnostic Tool (DDT)].

The engine/vehicle information that is monitored and available on the DATA LINK include the following:

Boost PressureCold Start StatusCoolant TemperatureCruise Control StatusCruise Control Set SpeedEngine IdentificationEngine Speed-rpmEngine Systems StatusFault ParameterFuel Consumption RateIdle Shutdown Timer Status

Calibration (road speed limit-mph, cruise control high speed set limit, cruise control low speed limit, PTO high limit) Fuel PressurePercent Rated TorquePercent ThrottlePTO Control StatusPTO Control Set RPMRetarder Enable Status

Calibration (rated speed-rpm and rated power-bhp) Vehicle Speed-mphVehicle Speed Limit Status

Either the Electronic Control Analyzer and Programmer (ECAP) or the Digital Diagnostic Tool (DDT), can be used to program the customer specified parameters.

One method of programming the customer specified parameters that are selected by a customer, the Electronic Control Analyzer and Programmer (ECAP), is used. The tool plugs into the data link connector to communicate with the ECM. The (ECAP) can be also be used to display real time values of all information available on the data link for diagnosing engine problems.

Programming of the customer specified parameters can be password protected to prevent unauthorized tampering or changing of the customer selected values. With the proper customer passwords, changing of limits such as Low Gears #1 RPM Limit (LoGr #1), Vehicle Speed Limit (VSL), Low Cruise Control Set Limit (LCC), etc. is quickly and easily accomplished. Reprogramming the ECM to operate within a different engine horsepower family requires a different personality module and engine iron changes. A Caterpillar dealer should be consulted for details.

An alternative method of programming the customer specified parameters that are selected by the customer can be done with the Digital Diagnostic Tool (DDT). This tool also plugs into the data link connector to communicate with the ECM. The DDT, however, does not accept alpha/numeric passwords (all "factory" passwords are alpha/numeric). Thus, the DDT cannot be used to program some engine parameters. Also, the DDT cannot be used to perform the electronic timing. The ECAP, with a 7X1200 Timing Adapter Group and an 8C9995 Plate, are required to perform electronic timing. See the topics, Checking Electronic Injection Timing With The Timing Adapter Tool Group And The ECAP, and Calibrating Electronic Injection Timing With The Timing Adapter Tool Group And The ECAP for a complete description of this procedure.

The DDT will read "active" or current diagnostic fault codes which are generated by the ECM. The ECAP will read current, as well as "logged" or intermittent diagnostic fault codes that the ECM generates. A partial list of the diagnostic fault codes is listed below.

System Fault Codes

For a complete listing of the diagnostic fault codes and an explanation of each, see 3176 Electronic Troubleshooting, Form No. SENR3913.

Retarder Enable (Jake Brake)

If the engine is equipped with a Jake Brake (engine retarder), the operation of it is provided through the RETARDER enable output. The RETARDER enable status is determined by the following inputs: a dash (brake) switch, a clutch switch, throttle position, a cruise switch, and engine rpm. Operation of the Jake Brake will be prohibited under unsafe engine operating conditions. Thus, if the engine speed is above 950 rpm, the driver's foot is off of the throttle pedal and clutch pedal, and the cruise switch is off, the Jake Brake will be enabled if the dash (brake) switch is energized. For a complete description of the Jake Brake, see the topic, Jake Brake (an attachment).

Diagnostic Lamp

The "check engine" light, on the truck dashboard, can be used as a diagnostic lamp to communicate status or operation problems of the electronic control system.

The "check engine" light will be ON and blink every five seconds whenever a diagnosistic fault is detected by the ECM. The light should also be On whenever the START switch is turned on, but the engine is not running. This condition will test whether the light is operating correctly.

If the "check engine" light comes on and stays on after initial start-up the 3176 has detected a system fault. The "check engine" light or service tools can be used to identify the diagnostic code.

The dash mounted cruise control switches are used to interrogate the ECM for system status. With the cruise control switch OFF, move the SET/RESUME switch to the RESUME position. The "check engine" light will begin to flash to indicate a 2-digit fault code while the SET/RESUME switch is held in the RESUME position. The sequence of flashes represents the system diagnostic message. The first sequence of flashes adds up to the first digit of the fault code. After a two second pause, a second sequence of flashes will occur which represents the second digit of the fault code. Any additional fault codes will follow, after a pause, and will be displayed in the same manner.

The "check engine" light is also used to monitor the idle shutdown timer. Ninety seconds before the programmed idle time is reached, the diagnostic lamp will start to flash at a rapid rate. If the clutch pedal or service brake pedal indicate a position change during this final ninety (90) seconds, (diagnostic lamp flashing), the idle shutdown timer will be disabled until the parking brake is again reset.

Electronic Control Module (ECM), Personality Module, and Transducer Module

Electronic Control Module (ECM)
(1) Fuel outlet. (2) Fuel inlet. (3) Engine wiring harness. (4) Fuel transfer pump. (5) Fuel pressure sensor. (6) ECM. (7) Personality module. (8) Transducer module. (9) Air inlet port. (10) Boost pressure inlet.

The engine uses a microprocessor based electronic control module which is isolation mounted on the rear left side of the cylinder block. The ECM (6) is cooled by fuel as it circulates through a manifold between two circuit boards in the control module. The fuel enters the control module, from fuel transfer pump (4), at fuel inlet (2), and exits the control module at fuel outlet (1).

One function that the ECM performs is a full range rpm governor. This electronic governor functions like a Caterpillar mechanical governor in the mid range. That is, there is some droop to provide the driver with "a feel for engine load". The throttle actuation characteristics are better than the mechanical governor since the linkage to the engine has been eliminated. The electronic governor includes the special features of programmable isochronous low idle and the elimination of governor overrun. Isochronous low idle control (constant engine rpm) is accomplished regardless of load at low idle. This feature makes it easier to start a loaded truck while on a steep grade. The electronic governor also reduces the mechanical governor overrun by using isochronous high idle control.

The 3176 has full authority over engine fuel delivery, and eliminates the mechanical fuel ratio control. Smoke limiting, white smoke control, and engine acceleration rates are more accurately defined electronically. The engine torque rise is tailored to limit peak torque and to match the engine performance to the transmission for good driveability. The engine output is programmed to provide constant horsepower over a large engine rpm range.

With the use of electronically controlled unit injectors, the 3176 provides total electronic control of fuel injection timing of the fuel. The injection timing is varied as a function of engine operating conditions to optimize the engine's performance for starting, emissions, noise, fuel consumption, and driveability.

All inputs and outputs to the ECM are designed to tolerate short circuits to battery voltage or ground without damage to the ECM. Resistance to radio frequency and electro-magnetic interference is designed into the 3176. The engine has passed tests for interference caused by police radars, two-way radios and other radio noise sources commonly encountered in on-highway applications.

The ECM power supply provides electrical power to all engine mounted sensors and actuators. Reverse voltage polarity protection and resistance to vehicle power system voltage "swings" or "surges" (due to sudden alternator load, etc.) have been designed into the ECM.

Wiring harness (3) provides communication or signal paths to the various sensors (coolant temperature, fuel pressure, speed/timing sensor), the data link connector, engine/vehicle connectors, and the unit injector solenoids connector.

The personality module (7), which is a part of the ECM, contains the operating program and performance maps for the engine. It provides the instructions necessary for the ECM to perform its function.

NOTE: The customer specified parameters include: engine power rating, vehicle identification number, PTO vehicle speed limit (PTO VSL), PTO engine RPM limit (PTO RPM), low gears #1 RPM limit (LoGr #1), low gears #2 RPM limit (LoGr #2), low gears turn off speeds (LoGr Off Limits), engine RPM at vehicle speed limit (Eng RPM at VSL), high gears RPM limit (HiGr RPM), top engine limit (TEL), vehicle speed limit (VSL), high gear turn on speed (HiGr On), low cruise control set limit (LCC), high cruise control speed set limit (HCC), idle shutdown timer, and retarder coast/latched. The customer specified parameters may be secured by customer passwords. A 3176 ECM may have all parameters programmed or any combination of parameters programmed. For a brief explanation of each of the customer specified parameters, see the Operation and Maintenance Manual.

The transducer module (8) is mounted directly to the ECM and includes a boost pressure sensor. Air pressure upstream of the turbocharger is routed to the transducer module to air inlet port (9). Turbo boost pressure is routed to boost pressure inlet (10) on the transducer module.

The ECM is programmed to run diagnostic tests on all inputs and outputs to partition a fault to a specific circuit (example, throttle position sensor or the harness connecting it to the ECM). Once a fault is detected, it can be displayed (flashing coded display, representing a diagnostic fault code) on the dash mounted diagnostic lamp (see the topic, Diagnostic Lamp), or the diagnostic fault code can be read using a service tool (ECAP or DDT). A multimeter can be used to check or troubleshoot most problems. The ECM also will log or record most diagnostic fault codes generated during engine operation. These logged or intermittent fault codes can be read by the ECAP.

Idle Shutdown Timer

The idle shutdown timer is a feature of the electronic control system that can be selected by the customer. This feature, one of the customer specified parameters, may be programmed by the ECAP service tool. The idle shutdown timer may be programmed from three (3) to sixty (60) minutes in one (1) minute increments.

The idle shutdown timer feature will shut down the engine after a time period specified by the customer. The following conditions must be met to enable the idle shutdown timer:

1. Idle shutdown timer feature has been selected.

2. Parking brake must be set.

3. Engine must be at operating temperature.

4. Vehicle speed must be at "0" mph.

5. No engine load.

6. Parking brake switch installed.

Ninety seconds before the programmed idle time is reached, the diagnostic lamp will start to flash at a rapid rate. If the clutch pedal or service brake pedal indicate a position change during this final ninety (90) seconds, (diagnostic lamp flashing), the idle shutdown timer will be disabled until the parking brake is again reset.

Throttle Position Sensor

Throttle Position Sensor

A cab mounted throttle position sensor is used to eliminate the mechanical linkage between the engine and the operators' foot pedal. The throttle position sensor is a rotary position sensor assembly which has 30° of active travel with and additional 5° of undertravel and 10° overtravel for linkage tolerance. It is environmentally protected for convenient mounting in the vehicle cab or on the engine side of the fire wall. The throttle position sensor output is a constant frequency pulse width modulated (PWM) signal rather than an analog voltage. The PWM signals overcomes the serious errors that can result from analog signals when pin to pin leakage or contamination occurs in the wiring harness and/or connectors.

The throttle position sensor has been designed to comply with FMVSS124 for throttle return under environmental temperature extremes and with part of the throttle linkage missing. Two return springs for the throttle position sensor are located behind the mounting disc. The engine returns to low idle if the PWM signal is invalid due to a broken or shorted wire.

Calibration of the throttle position sensor must be done manually. Refer to the Testing And Adjusting Section of this service manual for the correct procedure to calibrate the throttle position sensor.

Pedal-Mounted Throttle Sensor (If Equipped)

Pedal-Mounted Throttle Sensor

The Pedal-Mounted Throttle Sensor (if equipped) can be installed in place of the Throttle Position Sensor on earlier engines as long as the engine has the correct personality module.

The Pedal-Mounted Throttle Sensor is mounted on the back of the OEM-supplied pedal. Calibration of the Pedal-Mounted Throttle Sensor is done automatically by the ECM.

Vehicle Speed Buffer

Vehicle Speed Buffer

A buffer circuit is used to amplify and wave shape the output of the magnetic vehicle speed sensor. The vehicle speed buffer is designed to operate with a magnetic speed pickup that detects vehicle speed from a chopper wheel located on the transmission output shaft. The vehicle speed buffer prevents overloading of the magnetic pickup when multiple devices need to measure vehicle speed. The conditioned signal is transmitted to the ECM and other devices requiring vehicle speed. The buffer circuit should be located close to the magnetic speed pickup to minimize electrical noise interference.

The speedometer should receive its signal directly from the vehicle speed buffer. Cruise control, gear parameters, PTO, idle shutdown timer etc., may not function correctly if the speedometer is connected in some way other than the vehicle speed buffer.

Fuel System

Fuel System Schematic
(1) Vent plug. (2) Adapter (siphon break). (3) Electronically controlled unit injectors. (4) Fuel manifold (return path). (5) Fuel manifold (supply path). (6) Drain plug. (7) Pressure regulating relief valve. (8) Fuel tank. (9) Check valve. (10) Pressure relief valve. (11) Fuel transfer pump. (12) Electronic control module (ECM). (13) Fuel priming pump. (14) Fuel filter (remote mounted fuel filter as an attachment).

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 (3).

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 (5). 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) (2) 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 (4). 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 relief valve (7) is located between the fuel return manifold and the tank to maintain sufficient pressure in the system to fill the unit injectors.

Fuel System Components
(2) Adapter (siphon break). (4) Fuel return manifold. (5) Fuel supply manifold. (11) Fuel transfer pump. (12) Electronic control module (ECM). (13) Fuel priming pump. (14) Fuel filter (remote mounted fuel filter as an attachment). (15) Fuel outlet (to ECM). (16) Spacer block. (17) Fuel inlet (from tank). (18) Cover assembly.

The fuel transfer pump is located at the left rear corner of the engine. It is mounted to the spacer block (16) 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 cover assembly (18).

Fuel Lines Group
(2) Adapter (siphon break). (4) Fuel return manifold. (5) Fuel supply manifold. (7) Pressure regulating relief valve. (11) Fuel transfer pump. (12) ECM. (13) Fuel priming pump. (14) Fuel filter. (19) Cylinder head. (20) Plug. (21) Fuel out (from ECM). (22) Fuel in.

The fuel supply and return manifolds are drilled passages in a common manifold which is mounted to the cylinder head (19). Fuel from the fuel supply manifold 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 relief valve (7) which is a part of adapter (siphon break) (2). The pressure regulating valve controls the entire fuel system pressure, which in turn provides proper filling of the unit injectors.

Fuel System Electronic Control Circuit

Fuel System Electronic Control Circuit

The electronically controlled mechanically actuated unit injector fuel system provides total electronic control of injection timing. The injection timing is varied as a function of engine and vehicle operating conditions to optimize the engine's performance for starting, emissions, noise, fuel consumption, and driveability.

Engine speed is controlled by adjusting the firing duration. The speed sensor timing ring is part of the camshaft gear arrangement and provides information to the electronic control module (ECM), [with a signal picked up by the engine speed/timing sensor], for detection of camshaft position and engine speed. Thisdata, along with the other engine and vehicle inputs, allows the ECM to correctly and precisely send a signal to the injector solenoids. The unit injector's solenoid is energized to begin fuel injection or de-energized to end fuel injection. For a complete explanation of the injection process, see the topic, Electronically Controlled Unit Injector.

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. The fuel passes through the edge filter located between the fill port and the drilled passage leading into barrel (6). 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 deenergized 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) Valve cover base. (12) Turbocharger. (13) Oil inlet line. (14) 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 (12) 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 (13) 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 (14), 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).

Valve - 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 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) Lead wire connection (from Jake Brake logic to solenoid valve). (2) Solenoid valve. (3) Master piston. (4) Slave piston. (5) Control valve. (6) Exhaust bridge assembly. (7) Headbolt stud, spacer, and bolt. (8) Stud, and nut.

Exhaust Bridge Assembly
(9) Bridge assembly. (10) Screw and pin assembly. (11) Nut.

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 (8), and supported on the cylinder head with stud, spacer, and bolt (7). The exhaust bridge assembly (6) 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 (2) 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: one lead wire (1), one solenoid valve (2), two master pistons (3), two control valves (5), two exhaust bridge assemblies (6), one headbolt stud, spacer, and bolt (7), and two studs, and nuts (8).

The screw and pin assembly (10) is adjusted with nut (11) such that contact is made with the exhaust valve stem. 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 245 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 rockerarm 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.

Jake Brake Control

Jake Brake Control Circuit

The Jake Brake is activated by a signal, from the Jake Brake logic, to energize the Jake Brake housing solenoids. The Jake Brake logic receives input from the retarder enable line and the Jake Brake switches in the cab of the vehicle (on/off, and positions low, medium, and high). The retarder enable line status is determined by the ECM interfacing with information from three switches (clutch, brake, and cruise on/off), and the throttle position sensor.

The retarder enable line prohibits operation of the Jake Brake under unsafe engine operating conditions. Thus, if the engine speed is above 950 rpm, the driver's foot is off of the throttle pedal and clutch pedal, and the cruise switch is in the OFF position, the retarder enable line allows the Jake Brake logic to function, if the Jake Brake switches are closed.

A special Brake Assist function also allows the Jake Brake logic to operate the Jake Brake if the engine speed is above 950 rpm, the driver's foot is off the throttle pedal and the clutch pedal, the cruise switch is in the ON position, AND the service brake is pressed. The "Coast" or "Latched" options of the Brake Assist function is customer specified parameter. With the "Coast" option (this is the standard programmed parameter), the Jake Brake logic will operate the Jake Brake only when the driver presses the service brake pedal. As soon as the driver removes his foot from the service brake pedal, or another of the inputs to the Jake Brake is changed, the Jake Brake will stop operation. With the "Latched" option, the Jake Brake logic will operate the Jake Brake when the driver presses the service brake pedal, and will continue to operate it if he removes his foot from the service brake pedal until another of the inputs to the Jake Brake logic is changed.

With the Jake Brake switches closed, in the "low" position, the Jake Brake logic sends a signal to energize center Jake Brake housing solenoid, thus providing braking operation to cylinders 3 and 4. With the Jake Brake switches closed, in the "medium" position, the Jake Brake logic sends a signal to energize the two end housings' solenoids. This action will provide braking operation to cylinders 1, 2, 5, and 6. In the "high" position and the Jake Brake switches closed, the Jake Brake logic sends a signal to energize all three of the Jake Brake housings' solenoids, thus providing braking operation to all six cylinders of the engine.

Lubrication System

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

Engine-Right Side
(8) Main oil filter. (9) Oil pump. (10) Bypass oil filter. (12) Oil cooler. (16) Oil Filler. (17) Oil supply line to turbocharger (from cylinder block). (18) Oil drain line from turbocharger (to cylinder block). (19) Oil filter group.

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 (15), 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 (11) is thermostatic controlled to maintain 110°C (230°F) oil to bearing temperature. The high pressure relief valve (14), 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 (10) is a continuous flow 5 micron filter that returns 5 percent of the oil flow to the sump (13). The oil filter bypass valve opening pressure is 170 kPa (25 psi). 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 (17) (from the main oil gallery), and oil drain line (18) 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. 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 thisposition 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 5 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 blowby 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.

Right Side-Engine (inlet manifold removed)
(1) Temperature regulator housing. (4) Water pump. (5) Oil cooler. (6) Return manifold. (7) Supply manifold. (8) Coolant from oil cooler to supply manifold. Coolant to oil cooler from water pump.

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 plastic design with a powdered metal steel insert for the press fit to the water pump shaft. 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 flows 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. (14) Vent valve. (15) Open 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 (15), 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 valve (14) is located at the top portion of the return manifold, leading to the radiator outlet side of the temperature regulator housing. The vent valve assembly provides an air pressure balancing within the cooling system.

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) Outlet hose. (3) Inlet 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 temperature regulator housing (1), through inlet hose (3), into the coolant conditioner base. The "conditioned" or treated coolant then flows through outlet hose (2) into the outlet elbow from the oil cooler to the cylinder head. 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 an investment cast 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 Goetze 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. Lubrication of the piston pin is through a drilled passage in the shank of the rod from the rod journal bearing to the piston pin bearing. The large end bearing is steel backed aluminum with copper bonded lead tin overlay.

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 3176 electrical system schematic, see the 3176 Diesel Truck Engine Electrical Schematic module, Form No. SENR3912.

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 strap.

The engine alternator must be battery (-) grounded with a wire size adequate to handle full alternator charging current. The 3176 comes equipped with an alternator ground wire. The ground wire is attach to the cylinder head grounding stud (1).

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, vehicle speed buffer, 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.

Electronic Control Module Power Circuit

The ECM has been designed such that the ordinary switch input circuits to the ECM (cruise control on/off switch, brake switch, etc.) have a tolerance for resistance and shorts between wires. These tolerances are as follows:

1. The engine will tolerate resistance in any ordinary switch up to 2.5 Ohms without malfunctioning.

2. The engine will tolerate shorts to ground or between wires in any ordinary switch input (of 5000 Ohms or greater) without malfunctioning.

The ECM draws a maximum of 16 Amps at 12 Volts from the electrical system of the vehicle. However, the engine will function with less than 12 Volts. A minimum of 9 Volts is required while cranking, or when the engine is running.

Power enters the ECM through the positive BATTERY wire, and exits through the negative BATTERY wire. Negative BATTERY must be within .5 ohm of vehicle frame ground and must have a good direct path to the negative BATTERY terminal.

The engine is protected against power surges on the 12 Volt power supply due to alternator load dumps, air conditioner clutches, etc., and for jump starting with voltages up to 28 Volts.

Engine Speed/Timing Input Circuit

Engine rpm is sensed by an electronic sensor. The same sensor is also used for monitoring camshaft position which is used for injection timing control. The speed/timing sensor has self adjusting pickup head. The signal is generated by placing the sensor near the rotating Timing Reference Ring mounted on the camshaft. The ECM supplies the speed/timing sensor with 13.0 ± .5 VDC which it requires for proper operation.

The output of the speed/timing sensor is a series of pulses. The frequency of the pulses is dependent upon engine rpm. The ECM interprets the frequency of the pulses as engine rpm. Typically the frequency of this signal is 10 to 50 Hz (Hertz) while cranking and approximately 120 Hz at low idle. The shape of the pulses is dependent upon the rotation position of the camshaft. The ECM "reads" the shape of the pulses to determine camshaft position.

Coolant Temperature Input Circuit

Engine coolant temperature is measured by an electronic sensor mounted on the water outlet housing. This sensor signal is used to modify engine fueling and timing for improved cold start and while smoke cleanup. The ECM supplies the coolant temperature sensor with 8.0 ± .5 VDC and the sensor output voltage is .5 to 5.5 VDC depending upon engine coolant temperature.

Boost Pressure Input Circuit

The boost pressure sensor is located in the transducer module. Air from the engine inlet manifold is routed to this sensor. The output of the boost pressure sensor is a DC voltage of .8 to 5.0 Volts. This voltage is dependent upon the boost gage pressure measured by the ECM.

Throttle Position Input Circuit

Throttle position is obtained from an electronic sensor connected to the accelerator pedal. The 12 Volts operating voltage is provided to the sensor by the vehicle electrical system.

The output of the throttle position sensor is a constant frequency signal with voltage levels of .0 or 5 Volts. The pulse width, (not the frequency) of the signal is dependent upon the arm rotation of the throttle position sensor and is interpreted by the ECM as throttle position. The ECM interputs the minimum pulse width it sees (between 15% and 20%) as 3% throttle position and the maximum pulse width it sees (between 80% and 85%) as 100% throttle position.

The arm on the throttle position sensor has a maximum rotation of 45 degrees. The ECM only responds to a 30 degree active zone for interperting the throttle position. The throttle position sensor has a 5 degree lead in dead zone, a 30 degree active zone, and a 10 degree lead out zone. Mechanical stops on the accelerator pedal or the pedal linkage should restrict the throttle sensor rotation to within the active zone.

Injector Output Circuits

An electrical signal from the ECM controls each electronically controlled unit injector (EUI). "When" this electrical signal occurs determines fuel injection timing. The "duration" of the electrical signal determines the quantity of fuel injected.

The injector control signal is a 100 Volt pulse with a complex current shape which allows precise control of the injectors.

Check Engine Light (Diagnostic) Output Circuit

The engine/vehicle harness provides information about the engine to the "check engine" light on the vehicle dash. The light is ON when the ignition is on and the engine is not running, to verify that the light works. The light should go out about 10 seconds after the engine is started. If the engine light does not go out after the engine starts, an engine fault has been detected.

The cruise ON/OFF and Set/Resume switches can be used to interrogate the ECM for engine status. This is accomplished by placing the cruise ON/OFF switch in the OFF position and momentarily moving the Set/Resume switch to the RESUME position and then releasing it. The "check engine" light will emit a series of flashes which represent one or more, two digit numbers or diagnostic codes, which define engine status.

Twelve Volts is supplied to the "check engine" light from the vehicle electrical system. The ECM turns on the light by connecting one side of the bulb to ground which completes the electrical circuit.

Retarder Enable Output Circuit

The retarder enable output is a pulse width modulated (PWM) signal which informs the retarder electronics when it is "OK" (a safe engine and vehicle operating condition) to turn on the retarder. The status of this signal depends upon engine rpm, clutch position, service brakes, throttle position, and cruise switch positions.

Vehicle Speed Input Circuit

Vehicle speed is measured by a electromagnetic sensor, "reading" the rotation of gear teeth in the drive train of the vehicle. This sensor is provided by the vehicle manufacturer.

The output of the vehicle speed sensor is an AC voltage (the output voltage varies considerably, 0 to perhaps 50 Volts AC, but a 3 Volt AC signal is all that is required). The signal is sent to the vehicle speed buffer where it is modified and split into two separate and distinctly different signals: 1) The signal sent to the ECM is a 0 to 6 Volt DC pulse which is interpreted as vehicle speed. 2) The other signal is 3.0 Volts AC and can be used by the vehicle manufacturer for use with electronic speedometers, or trip recorders, or service tools.

The 12 Volts operating voltage required by the vehicle speed buffer is supplied by the vehicle electrical system.

Cruise Control On/Off Input Circuit

The cruise control (CC) and power take-off (PTO) ON/OFF input is an ordinary switch. With this switch in the ON position, it is possible to "activate" the cruise control or power take-off mode if other ECM programmed conditions are met.

With this switch "open" (or OFF), the input line to the ECM will go to approximately 5 volts. With the switch "closed" (or ON), the input line to the ECM will go to 0 volts (ground).

Cruise Control Set/Resume Input Circuit

The cruise control and power take-off set/resume is provided by a three position switch. The switch is used to SET vehicle speed or engine rpm. The function of each position of the switch is as follows:

1) CENTER POSITION, the set/resume switch is "open" and all inputs are inactive.

2) SET POSITION, after the switch is moved to the SET position and released, the ECM will maintain the existing engine rpm (determining vehicle speed) when the switch was released. If the engine is held in the SET position, the ECM will gradually increase engine rpm (determining vehicle speed) until the switch is released.

3) RESUME POSITION, if cruise is deactivated by application of the clutch or service brake, and the switch is then moved to the RESUME position and released, the cruise (PTO) mode is reactivated to the last setting. If the switch is held in the RESUME position, the ECM will gradually decrease engine rpm (determining vehicle speed) until the switch is released.

With this switch "open" (or OFF), the input line to the ECM will go to approximately 5 volts. With the switch "closed" (or ON), the input line to the ECM will go to 0 volts (ground).

Vehicle Switches Input Circuits

The brake switch is used to deactivate the cruise or PTO modes when the vehicle service brakes are applied. The brake switch is also used to activate the retarder enable output if the service brakes are applied while in cruise mode.

The clutch switch is used to deactivate the cruise or PTO modes when the clutch pedal is pressed. The clutch switch is used to DEACTIVATE the retarder enable circuit.

With this switch "open" (or OFF), the input line to the EMC will go to approximately 5 volts. With the switch "closed" (or ON), the input line to the EMC will go to 0 volts (ground).

Fuel Pressure Input Circuit

Fuel pressure is monitored after the filter by the fuel pressure sensor which is located on the fuel filter housing. The 5 Volt DC operating voltage for this sensor is supplied by the ECM. The output of the fuel pressure sensor is a .5 to 4.5 Volts DC signal. The voltage is dependent upon fuel pressure and is interpreted by the ECM as fuel pressure. If fuel pressure is less than 445 kPa (65 psi) at rated rpm, the "check engine" light is turned on.

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 circuits 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 winding, 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 eletromagnetic 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 oftime 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.