3176C & 3196 MARINE ENGINES Caterpillar


Systems Operation

Usage:



Engine Design


Cylinder And Valve Location. (A) Exhaust valves and (B) Inlet valves.

3176C Marine Engine

Bore ... 125.0 mm (4.90 in)

Stroke ... 140.0 mm (5.50 in)

Displacement ... 10.3 liter (628.3 cubic inch)

Cylinder Arrangement ... in-line 6 cylinder

Valves per Cylinder ... 4

Valve Lash Setting

Inlet ... 0.38 ± 0.08 mm (.015 ± 0.003 in)

Exhaust ... 0.76 ± 0.08 mm (.030 ± 0.003 in)

Type of Combustion ... Direct Injection

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

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

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


Cylinder And Valve Location. (A) Exhaust valves and (B) Inlet valves.

3196 Marine Engine

Bore ... 130.0 mm (5.12 in)

Stroke ... 150.0 mm (5.91 in)

Displacement ... 12.0 liter (732 cubic inch)

Cylinder Arrangement ... in-line 6

Valves per Cylinder ... 4

Valve Lash Setting

Inlet ... 0.38 ± 0.08 mm (.015 ± 0.003 in)

Exhaust ... 0.76 ± 0.08 mm (.030 ± 0.003 in)

Type of Combustion ... Direct Injection

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

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

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

General Information

NOTE: For specifications, refer to the Specifications For 3176C & 3196 Marine Engines, RENR1231. If the Specifications in RENR1231 are not the same as in the Systems Operation, Testing & 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 engines are electronically controlled mechanically actuated unit injector diesel engines. The engine is an inline 6 cylinder arrangement with a bore of 130.0 mm (5.12 in) and a stroke of 150.0 mm (5.91 in) giving a total displacement of 11.95 L (747 cu in). The engine as configured is a low profile arrangement with the exhaust and inlet manifolds on the right hand side.

The electronic unit injector system provides increased control of timing and fuel/air ratio control. Timing advance is achieved by precise control of injector timing. Engine rpm is controlled by adjusting the injection duration. A special pulse wheel provides information to the electronic control module for detection of cylinder position and engine rpm.

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

Starting The Engine

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


NOTICE

Excessive ether (starting fluid) can cause piston and ring damage. Use ether for cold weather starting purposes only.


Cold Mode Operation

The engine control system performs a cold start strategy for the correct warm up time after a cold engine start [approximately less than 17°C (63°F)]. Once activated this "cold start" strategy (known as "cold mode") will increase the idle rpm to 1200 rpm, until the coolant temperature rises above 18°C (64°F), or until the engine has been running for 5 minutes. It also varies fuel injection amount and timing for maximum startup and white smoke control. The time needed for the engine to reach the normal mode of operation is usually less than the time taken for a walk-around-inspection of the engine.


NOTICE

A vessel equipped with a 3176C or a 3196 Marine Engine should not be moved until it is out of the cold mode. If the vessel is operated while in cold mode, power will be noticeably reduced. While in the cold mode, the low idle will be reduced to the customer programmed low idle and the power will still be reduced.


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 operated at low rpm and low power demand than when idled at no load. Typically, the engine should be up to operating temperature within a few minutes.

Customer Specified Parameters

The engine is capable of being programmed for several customer specified parameters. For a complete list of the customer specified parameters see the topic: Electronic Control Module (ECM), and Personality Module. For a brief explanation of each of the customer specified parameters, see the Operation and Maintenance Manual.

Glossary Of Electronic Control Terms

After Market Device
As used here, a device or accessory installed by the customer or vessel OEM after the engine is delivered.
Alternating Current (AC)
The direction of current flow changes (alternates) regularly and constantly.
American Wire Gauge (AWG)
A measure of the diameter (and therefore the current carrying ability) of electrical wire. The smaller the AWG number, the larger the wire.
Atmospheric Pressure Sensor
This sensor measures atmospheric air pressure in the crankcase and sends a signal to the ECM.
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 ECM.
Bypass Circuit
A circuit, usually temporary, to substitute for an existing circuit, typically for test purposes.
Calibration
As used here, is an electronic adjustment of a sensor signal.
Caterpillar Engine Monitoring
The part of the Caterpillar Electronic Engine Control that monitors Coolant Temperature, Oil Pressure, Inlet Manifold Air Temperature and Coolant Level to flag the operator of detected problems. The Coolant Temperature, Inlet Manifold Air Temperature, and Oil Pressure Sensors are supplied by Caterpillar and monitored by the ECM. The Coolant Level Sensor is OEM installed, but still monitored by the ECM. This is opposed to an after market Engine Monitoring System which does not interface with the Caterpillar Electronic Engine Control.
Check Engine Lamp
Sometimes referred to as the "Diagnostic Lamp", it is used to warn the operator of the presence of an active diagnostic code.
Coolant Level Sensor
This sensor detects the absence/presence of coolant at the probe and sends a signal to the ECM.
Code
See Diagnostic Code.
Coolant Temperature Sensor
This sensor detects the engine coolant temperature for Cold Mode operation and Caterpillar Engine Monitoring (provided the Engine Monitoring is not programmed OFF).
Custom Data
Part of the ECM stored trip, it allows the owner to specify operating parameters of the engine application while in service. This data is for monitoring purposes.
Customer Specified Parameter
A Parameter that can be changed and whose value is set by the customer and protected by Customer Passwords.
Data Link
An electrical connection for communication with other microprocessor based devices that are compatible with a SAE Standards such as trip recorders, electronic dashboards and maintenance systems. A 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/Timing Sensor 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 electronic system.
Diagnostic Event Code
These codes indicate an event. They are not necessarily (or usually) an indication of problem with in the electronic system.
Diagnostic Fault Code
These codes indicate an electronic system malfunction indicating a problem with the electronic system.
Diagnostic Flash Code
These codes are flashed out using the Check Engine/Diagnostic Lamp to indicate an electronic system malfunction or an event detected by the electronic system.
Diagnostic Lamp
Sometimes referred to as the Check Engine Lamp, it is used to warn the operator of the presence of an active diagnostic code.
Direct Current (DC)
The type of current where the direction of current flow is consistently in one direction only.
Dual Coil Speed Sensor
A magnetic pickup that senses movement of the teeth on the output shaft of the transmission. It contains two coils, one to supply a signal to the speedometer, and one for the speed buffer.
Duty Cycle
See Pulse Width Modulation.
Electronic Control Analyzer Programmer (ECAP)
An electronic service tool developed by Caterpillar used for programming and diagnosing a variety of Caterpillar electronic controls.
Electronic Control Module (ECM)
The engine control computer that provides power to the system electronic, monitors system 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.
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 Technician (CAT ET)
A software program to run on a service tool like a personal computer (PC). This program will supplement and eventually replace ECAP.
Engine Speed/Timing Sensor
Provides a Pulse Width Modulated Signal to the ECM, which the ECM interprets as crankshaft position and engine speed.
Failure Mode Identifier (FMI)
Type of failure the component experienced (adopted from SAE standard practice J1587 diagnostics).
Flash Code (FC)
The Caterpillar proprietary code numbers which are flashed out on the diagnostic lamp.
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. It is based on Desired RPM, FRC Fuel Position, rated fuel position and engine rpm.
Fuel Temperature Sensor
This sensor detects the fuel temperature. The ECM monitors the fuel temperature and adjusts calculated fuel rate accordingly.
Full Load Setting (FLS)
Number representing fuel system adjustment made at the factory to "fine tune" the fuel system. Correct value for this parameter is stamped on the 9L6531 Engine Information Label. This parameter must be programmed or a Diagnostic Code 253-02 Check Customer Or System Parameters (Fault Code 56) will be generated.
Full Torque Setting (FTS)
Similar to Full Load Setting. This parameter must be programmed or a Diagnostic Code 253-02 Check Customer Or System Parameters (Fault Code 56) will be generated.
Harness
The wiring bundle (loom) connecting all components of the electronic system.
Histogram
A bar graph indicating the relative frequency of engine operation in specific operating ranges.
Inlet Manifold Air Temperature Sensor
This sensor detects the inlet manifold air temperature. The ECM monitors the inlet air temperature and coolant temperature to adjust injection timing. It is also part of Caterpillar Engine Monitoring and cooling fan control (optional).
Integrated Electronic Controls
The engine is designed with the electronic controls as a necessary part of the system. The engine will not operate without the electronic controls.
Oil Pressure Sensor
This sensor measure engine oil pressure and sends a signal to the ECM as part of Caterpillar Engine Monitoring.
Open Circuit
Condition where an electrical wire or connecting 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 vessel in which a Caterpillar engine is installed.
Parameter
A programmable value which affects the characteristics, performance or behavior of the engine.
Passive Magnetic Speed Sensor
A speed sensor not requiring a power and ground connection. It produces a signal based on the change in magnetic flux of a ferrous metal gear near the sensing tip.
Password
A group of numeric or alpha-numeric characters, designed to restrict access to parameters. The electronics system requires correct passwords in order to change Customer Specified Parameters (Customer Passwords) or certain engine specifications (Factory Passwords). Passwords are also required to clear certain diagnostic codes.
Parameter Identifier (PID)
Two or three digit code which is assigned to each component.
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").
Rated Fuel Position
("Rated Fuel Pos" on electronic service tool) - 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.
Remote Mounted Throttle Position Sensor
This sensor measures throttle position and sends a signal to the ECM. The sensor is mounted to the throttle assembly. See Throttle Position Sensor.
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 electronic service tool to a specific application.
Short Circuit
A condition where an electrical circuit is unintentionally connected to an undesirable point.
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.
Speed Circuit
Includes the speed sensor, harness and ECM.
Speed Sensor
An electromagnetic pickup that measures speed from the rotation of gear teeth in the drive train.
Standard SAE Diagnostic Communications Data Link
Refer to ATA Data Link.
Subsystem
As used here, it is a part of the engine system that relates to a particular function, for instance the throttle subsystem, etc.
Supply Voltage
A constant voltage supplied to a component to provide electrical power for its operation. It may be generated by the ECM, or it may be vessel battery voltage supplied by the vessel 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 interpretation of the signal from the Throttle Position Sensor.
Throttle Position Sensor
An electronic sensor which is connected to the throttle and sends a Pulse Width Modulated Signal to the ECM.
Total Tattletale
Total number of changes to all Customer Specified Parameters.
Transducer
A device which converts a mechanical signal to an electrical signal.
Trip Recorder
A device dedicated to recording engine operating parameters during service. Used to analyze operating habits and produce operator logs.
Warning Lamp
Used to warn the operator of the presence of a Caterpillar Engine Monitoring detected problem.

Model Views


Right Side View


Left Side View


Top View

Electronic Control System

Electronic Control System Components


Top View
(1) Primary speed/timing sensor. (2) Coolant temperature sensor. (3) Boost pressure sensor. (4) Inlet air temperature sensor. (5) Coolant level sensor. (6) Backup speed/timing sensor. (7) Fuel temperature sensor. (8) Atmospheric pressure sensor.


Left Side View
(4) Inlet air temperature sensor. (5) Coolant level sensor. (6) Backup speed/timing sensor. (7) Fuel temperature sensor. (8) Atmospheric pressure sensor. (9) Engine wiring harness. (10) ECM.


Front View
(1) Primary speed/timing sensor. (2) Coolant temperature sensor. (3) Boost pressure sensor. (4) Inlet air temperature sensor. (6) Backup speed/timing sensor. (7) Fuel temperature sensor.


Right Side View
(1) Primary speed/timing sensor. (11) Fuel pressure sensor. (12) Oil pressure sensor.

Major components of the electronic control system are: (1) Primary speed/timing sensor, (2) Coolant temperature sensor, (3) Boost pressure sensor, (4) Inlet air temperature sensor, (5) Coolant level sensor, (6) Backup speed/timing sensor, (7) Fuel temperature sensor, (8) Atmospheric pressure sensor, (9) Engine wiring harness, (10) ECM, (11) Fuel pressure sensor, (12) Oil pressure sensor 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 engine (examples are: speed/timing sensor, coolant temperature sensor, etc.). The electronic control module sees the input sensor signal as information about the condition, environment, or operation of the engine.

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

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

Electrical Connectors And Functions

Fuel System


Fuel System Schematic
(1) Fuel filter base. (2) Siphon break. (3) Vent plug. (4) Electronically controlled unit injectors. (5) Fuel supply manifold. (6) Drain plug. (7) Fuel priming pump. (8) Fuel return manifold. (9) Fuel filter (secondary). (10) Fuel regulating valve. (11) Flow return orifice. (12) Electronic control module (ECM). (13) Fuel transfer pump. (14) Pressure regulating valve. (15) Check valve. (16) Fuel tank.

The fuel supply circuit is a conventional design for unit injected engines, in that it uses a fixed clearance gear type fuel transfer pump (13) to deliver fuel from the fuel tank to the electronically controlled unit injectors (4). Fuel is pulled from the fuel tank by the fuel transfer pump. The fuel transfer pump incorporates a check valve (15) to permit fuel flow around the gears for hand priming and a pressure regulating valve (14) to protect the system from extreme pressure. The excess fuel flow provided by the fuel transfer pump cools and purges the air from the unit injectors.

The fuel flows from the fuel transfer pump through cored passages in the housing of the electronic control module (ECM) (12) to cool the module, and then through a five micron fuel filter (9). A fuel priming pump (7) is located on the fuel filter base to fill the system after draining the fuel supply and return manifolds to replace unit injectors. The fuel filter base (1) also incorporates a siphon break (2) that prevents fuel from siphoning from the cylinder head during long periods of storage. The fuel priming pump (7) minimizes fuel drainback to tank with two check valves.

The fuel flows continuously from the fuel supply manifold through the unit injectors and is returned to the tank by the fuel return manifold (8). 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 flow regulating orifice is located in adapter manifold to maintain sufficient back pressure in the system to fill the unit injectors. Optimal fuel flow is provided to the unit injectors without excessive fuel tank heating.

The fuel transfer pump (13) is located at the left front lower corner of the engine. It is driven by the lower accessory drive gear.

The fuel supply and return manifolds are drilled passages in a common manifold which is mounted to the cylinder head. Fuel from the fuel supply manifold (5) flows through drilled passages within projections in the cylinder head casting, and into the electronically controlled unit injectors (4).

At the end of the fuel return manifold (8) is a flow return orifice (11) which is a part of fuel filter base (1). The flow pressure regulating orifice maintains back pressure to fill the unit injectors and provides a constant fuel flow through the injectors.

Fuel System Electronic Control Circuit


3176C & 3196 Marine Engines Electronic Governor

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

Electronic Controls

The 3176C & 3196 Marine 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/injectors to "act") to control the engine. Neither one can do anything by itself.

The ECM determines a "desired rpm" based on the throttle signal and certain diagnostic codes. The ECM then maintains the desired engine rpm by sensing actual engine rpm and deciding how much fuel to inject in order to achieve the desired rpm.

Fuel Injection

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

The ECM sets certain limits on the amount of fuel that can be injected. "FRC Fuel Pos" is a limit based on boost pressure to control the fuel/air ratio, for emissions control purposes. When the ECM senses a higher boost pressure (more air into cylinder), it increases the "FRC Fuel Pos" limit (allows more fuel into cylinder). "Rated Fuel Pos" is a limit based on the horsepower rating of the engine. It is similar to the rack stops and torque spring on a mechanically-governed engine. It provides horsepower and torque curves for a specific engine family and rating.

There are three levels of fuel/air ratio that can be selected by the customer.

Level 1: Minimum smoke.

Level 2: Default setting from the factory.

Level 3: Maximum acceleration.

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

Unit Injector Mechanism


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

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 inlet and exhaust valves, and one operates the unit injector mechanism. Force is transmitted from the unit injector lobe on camshaft (7), through lifter (6), to pushrod (4). From the pushrod, 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 & Adjusting Section for proper setting of the injector lash.

Electronically Controlled Unit Injector


Electronically Controlled Unit Injector
(1) Electrical connection. (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) Tip. (12) Check valve.

Low pressure fuel from the fuel supply manifold (through drilled passages in the cylinder head), enters the electronically controlled unit injector at the fill port. As the unit injector mechanism produces force to the top of the unit injector, spring (3) is compressed, and plunger (5) is driven downward, displacing fuel through valve (4) into the return manifold to the tank. The fill passage into barrel (6) is closed by the outside diameter of the plunger, and the passages within the tip (11) and along check valve (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 electrical 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 electrical connection, the solenoid valve assembly is de-energized and valve (4) is opened. Now, the high pressure fuel is dumped through the spill port to the fuel return manifold and tank. The check in the injector tip seats and injection is ended, as the fuel pressure decreases to 25 517 kPa (3700 psi) and below.

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

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

Air Inlet And Exhaust System


Air Inlet And Exhaust System Schematic
(1) Inlet valves. (2) Exhaust valves. (3) Inlet manifold. (4) Exhaust manifold. (5) Sea water inlet. (6) Sea water outlet. (7) Aftercooler. (8) Air inlet. (9) Exhaust outlet. (10) Turbocharger compressor wheel. (11) Turbocharger turbine wheel.


Air Inlet And Exhaust System Components
(3) Inlet manifold. (8) Air inlet. (10) Turbocharger compressor wheel. (11) Turbocharger turbine wheel. (12) Air cleaner.


Air Inlet And Exhaust System Components
(4) Exhaust manifold. (6) Sea water outlet. (7) Aftercooler. (9) Exhaust outlet. (13) Turbocharger oil inlet line. (14) Turbocharger oil drain line.


Air Inlet And Exhaust System Components
(5) Sea water inlet.

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. 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 (8) by turbocharger compressor wheel (10). Here the air is compressed and heated, and forced on to aftercooler (7). 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 (3). Air flow from the inlet chambers into the cylinders is controlled by inlet valves (1). There are two inlet valves (1) and two exhaust valves (2) in the cylinder head for each cylinder. Inlet valves open when the piston moves down on the inlet stroke. When the inlet valves open, cooled compressed air from the inlet chamber within the inlet manifold is pulled into the cylinder. The inlet 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 (4). 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 (11) to turn. The turbine wheel is connected to the shaft that drives the compressor wheel. Exhaust gases from the turbocharger pass through exhaust outlet (9).

Turbocharger

The turbocharger is mounted to the exhaust manifold of the engine. All the exhaust gases go from the exhaust manifold through the turbocharger.

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 in the turbocharger use engine oil under pressure for lubrication. The oil flows through an oil inlet line and into oil inlet port in the center section of the cartridge for lubrication of the bearings. Oil leaves the turbocharger through an oil outlet port and oil drain line, returning to the engine block.

Valves And Valve Mechanism


Valve Mechanism
(1) Inlet valve bridge. (2) Rotocoil. (3) Inlet rocker arm. (4) Pushrod. (5) Valve springs (inner and outer). (6) Inlet 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 inlet 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 inlet and exhaust valves, and one operates the unit injector mechanism. As the camshaft turns, the inlet cam lobe causes lifter (9) to move pushrod (4) up and down. Upward movement of the pushrod against inlet rocker arm (3) transmits a downward force on inlet valve bridge (1) and a downward movement on the two inlet valves (6), opening them. The inlet valve bridge moves up and down on a dowel mounted in the cylinder head.

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


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

Lubrication System


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


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

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

The engine oil cooler bypass valve (12) is thermostatic controlled to maintain 110°C (230°F) oil to bearing temperature. The high pressure relief valve (15), located in the filter base, protects the filters and other components during cold starts. The high pressure relief valve opening pressure is 695 kPa (100 psi) pressure. The bypass oil filter (11) is a continuous flow 5 micron filter that returns 5 percent of the oil flow to the oil pan (sump) (14). The engine oil filter bypass valve (6) opening pressure is 170 kPa (25 psi). An engine oil pressure sensor is part of the Electronic Engine Protection Package. Another feature of the lubrication system is that the symmetrical oil pan can be installed as front or rear sump.

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

Oil Flow Through The Lubrication System


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

The engine 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 engine oil pump bypass valve (15) on its way to the engine oil cooler. The bypass valve controls the oil pressure from the engine oil pump. The engine 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 engine oil cooler which has coolant flowing through it to cool the oil. The thermostat controlled engine oil cooler bypass valve (14) directs the oil flow through the engine oil cooler when the oil temperature reaches 100 to 103°C (212 to 217°F). A fail safe activation temperature [127°C (260°F)] incorporated in the valve will close the valve, directing oil flow to the engine oil cooler. The valve will remain at this position if it has failed. The bypass valve is also pressure activated. If oil pressure differential across the engine oil cooler reaches 155 ± 17 kPa (22 ± 3 psi), the valve will open and allow oil flow to bypass the engine oil cooler.

If desired with the use of bypass oil filter, approximately five percent of the oil flow is directed through an orifice [passage to bypass filter (17)], then through the bypass filter and to the sump. The main oil flow now reaches the main engine oil filter. When the oil pressure differential across the engine oil filter bypass valve (12) reaches 170 kPa (25 psi), the valve allows the oil flow to go around the main engine 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 engine oil filter. The bypass valve will also open when there is a restriction in the engine oil filter. This action does not let an engine oil filter with a restriction prevent lubrication of the engine.

NOTE: See the topic, Engine Oil Filter Group in the Specifications, for a cross section of the engine 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
(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 (19) and the cavity behind the ring grooves in the crown. The piston cooling jet (18) 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) Vacuum limiter.

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 separator housing. This prevents pressure from building up that could cause seals or gaskets to leak.

Crankcase Ventilation And Fumes Disposal

The 3176C & 3196 Marine Engines use a closed crankcase emission system incorporated within the air cleaner unit. This system eliminates crankcase vapors in the engine room by separating the oil from the dry gases, returning the oil to the crankcase and directing the dry gases to the inlet air.

The system is entirely enclosed and virtually maintenance free. Refer to the Operation & Maintenance for the cleaning interval for the air filter elements. The system consists of three major components: air cleaner, vacuum limiter and a separator housing. The air cleaner is easily removed for cleaning and re-use.

As inlet air passes through the air cleaner to the turbocharger, a slight vacuum is created within the separator housing. Crankcase fumes are drawn out of the engine breather through a hose connected to this low pressure area in the separator housing. Once in the separator housing, the oil vapor is removed from the gases and returned to the crankcase through a drain line. Crankcase vacuum is maintained at .4 kPa (1.5 inches of H2O) by the vacuum limiter. A check valve in the oil drain line prevents oil from being drawn into the separator. As restriction in the air filter builds up, fresh air is drawn in through the vacuum limiter to maintain the .4 kPa (1.5 inches of H2O) if vacuum into the crankcase.

Cooling System

Coolant Flow


Cooling System Schematic
(A) Sea water. (B) Jacket water. (C) Air flow. (1) Sea water pump. (2) Aftercooler. (3) Heat exchanger. (4) Marine gear oil cooler. (5) Water cooled exhaust. (6) Fuel cooler. (7) Turbocharger air inlet. (8) Water return manifold. (9) Turbocharger exhaust. (10) Water cooled exhaust manifold. (11) Engine. (12) Engine oil cooler. (13) Jacket water pump.

A gear driven jacket water pump (13) located in the right hand side of the engine supplies the coolant for the engine cooling system. The coolant is supplied to the engine oil cooler (12), engine (11), water cooled exhaust manifold (10) and to the turbocharger exhaust (9). Water is then collected in the water return manifold (8) and routed to the heat exchanger (3).

Sea water flows in thru the fuel cooler (6) and to the sea water pump (1). The sea water pump (1) directs the flow of sea water to aftercooler (2), heat exchanger (3), marine gear oil cooler (4), and water cooled exhaust (5).


Left Side Of Engine
(1) Sea water pump.


Front Of Engine
(2) Aftercooler. (3) Heat exchanger.


(13) Jacket water pump. (14) Temperature regulator housing. (15) Coolant from engine oil cooler to water pump.

Coolant is pulled from the heat exchanger (3) into jacket water pump (13) by impeller action. The water pump is located on the cylinder block side of the front timing gear housing on the right hand side of the engine. It is gear driven, at 1.14 times engine speed by an idler which is turned by the crankshaft gear. The water pump shaft is supported by two ball bearings located in the water pump housing and front timing gear cover. The water pump impeller is a closed face, radial vane cast iron design. The water pump housing and volute housing are aluminum die castings. A cartridge type water pump seal is located on the inlet side of the pump to provide good water flow around the seal for cooling. It can be replaced by removing the volute housing and pulling the impeller from the shaft.

The coolant is pumped through engine oil cooler (12), turbocharger exhaust (9), water cooled exhaust manifold (10), and then to the engine (11). The engine 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 the water return manifold (8). The return manifold collects the coolant from each cylinder and directs the flow to temperature regulator housing (14). With the temperature regulator in the closed position, coolant flows through the regulator, bypassing the heat exchanger, and back to the water pump for recirculation. With the temperature regulator in the open position, the coolant is directed through the heat exchanger and back to the water pump inlet.

The sea water pump supplies a continuous flow of water through the aftercooler to the heat exchanger for cooling. Sea water is drawn in through the pump inlet and is discharged into the aftercooler and then the heat exchanger.

Temperature Regulator Housing


Engine-Front Right Side (Typical Example)
(1) Temperature regulator housing. (2) Bypass tube.


Temperature Regulator Housing
(3) Return manifold. (4) Closed position.

The coolant temperature regulator is the full flow bypass type installed for outlet temperature regulation of the coolant. With the valve in closed position (4), the engine is cold, the coolant flows through the regulator [from return manifold (3)], bypassing the heat exchanger, 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 heat exchanger and bypassing the remainder to the water pump inlet. At full operating temperature of the engine, the valve moves to the open position, and all the coolant flow is directed to the heat exchanger and then back to the water pump inlet providing maximum heat release from the coolant.

Basic Block

Cylinder Block And Head

The cylinder block has a unique design with a deep counterbore supporting the cylinder liner and forming the coolant jacket. Two oil manifolds are provided in the cylinder block for engine lubrication. The lower right side manifold supplies oil for the piston cooling jets and the crankshaft bearings along with a direct passage to the oil filter base. The upper left side manifold supplies oil for the camshaft bearings and valve mechanism. The oil supply for the left manifold is from the right manifold through crescent cuts above the number one and number four main bearings.

The cylinder liner is a mid-supported design seated on a counterbored shelf in the block between the crankcase and coolant jacket and is piloted above the shelf face. Sealing of the coolant jacket is located at the upper and middle regions of the liner. The lower barrier is above the block/liner seating surface and uses a "D" cross section seal located in the cylinder liner flange diameter. The upper barrier is above the coolant jacket and uses the head gasket body as the upper sealing barrier.

Pistons, Rings And Connecting Rods

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

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

Crankshaft

The crankshaft converts the cylinder combustion forces into rotating torque which powers equipment. On this engine, a vibration damper is used at the front of the crankshaft to reduce torsional vibrations (twist on the crankshaft) that can cause damage to the engine.

The crankshaft drives a group of gears (front gear train) on the front of the engine. The front gear train provides power for the camshaft, water pump, engine oil pump and fuel transfer 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 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 and uses 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 inlet valves. The camshaft is supported in the cylinder block in seven bearing fitted 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 cylinder block. A thrust pin located at the rear, supported by the cylinder block, positions the camshaft through a circumferential groove machined at the rear of camshaft. 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 electrical system schematic, refer SENR1171, 3176C & 3196 Marine Engines Schematic.

Grounding Practices

Grounding (Minus Battery Bus Bar Connections)


NOTICE

All negative battery connections MUST have a common ground that terminates at the negative battery bus bar. Refer to Battery Circuit Requirements And Considerations: Grounding in this guide for additional information.


Proper grounding for vessel and engine electrical systems is necessary for engine/vessel performance and reliability. The problems with intermittent power connections are often very difficult to diagnose and repair.


NOTICE

Improper grounding will cause uncontrolled and unreliable circuit paths. This can result in damage to the engine crankshaft main bearings, crankshaft journal surfaces or other engine components. This may also cause electrical activity which may degrade vessel electronics and communication equipment.


The alternator, starting motor, and all electrical systems MUST be grounded to -Battery. The alternator and starting motor must also meet marine isolation requirements. For engines which have an alternator grounded to an engine component, a ground strap MUST connect that component to -Battery and the component MUST be electrically isolated from the engine.

A Bus Bar with a direct path to -Battery is permissible and recommended to use for all common ground connections. Refer to Power Supply Connections to Start (Ignition) Switch(es) and Starting Motor in this guide for additional information.

Operator Station Grounding Connections

The engine ECM in the engine room must be connected to -Battery Bus Bar. Caterpillar recommends a dedicated bus bar for all engine ECM connected electronics as well. This connection ensures that the ECM and all components, including switches, sensors and electronic display modules have a common reference point.


Figure 1 - Operator Station Battery Grounding

Wire Size Requirements

The wire size (AWG) to battery bus bar to which components are grounded MUST be of adequate size to handle maximum current for the circuit.

Engine Electrical System

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

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

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

The low amperage circuit and the charging circuit are both connected through the ammeter. The starting circuit is not connected through the ammeter.

Charging System Components

Alternator

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

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

The rotor assembly has many magnetic poles like fingers with air space between each opposite pole. The poles have residual magnetism (like permanent magnets) that produce a small amount of magnetic 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.


NOTICE

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



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

Starting System Components

Solenoid


Typical Solenoid Schematic

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

a. Closes the high current starting motor circuit with a low current start switch circuit.
b. Engages the starting 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 starting motor begins to turn the flywheel of the engine.

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

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

Starting Motor

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

The starting 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 starting motor. When the circuit between the battery and the starting motor is complete, the pinion will turn the engine flywheel. A clutch gives protection for the starting motor so that the engine can not turn the starting motor too fast. When the start switch is released, the starter pinion will move away from the ring gear.


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

Air Starting System

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


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

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

For engines which do not have heavy loads when starting, the regulator setting is approximately 690 kPa (100 psi). This setting gives a good relationship between cranking speeds fast enough for easy starting and the length of time the air starting motor can turn the engine flywheel before the air supply is gone.

If the engine has a heavy load which can not be disconnected during starting, the setting of the air pressure regulating valve needs to be higher in order to get high enough speed for easy starting.

The air consumption is directly related to speed; the air pressure is related to the effort necessary to turn the engine flywheel. The setting of the air pressure regulator can be up to 1030 kPa (150 psi) if necessary to get the correct cranking speed for a heavily loaded engine. With the correct setting, the air starting motor can turn the heavily loaded engine as fast and as long as it can turn a lightly loaded engine.

Other air supplies can be used if they have the correct pressure and volume. For good life of the air starting motor, the supply should be free of dirt and water.

The lubricator uses diesel fuel, which is supplied by a line from the fuel filter, as a lubricant. The maximum pressure for use in the air starting motor is 1030 kPa (150 psi).


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

The air from the supply goes to relay valve (3). The air start control valve (1) is connected to the line before the relay valve. The flow of air is stopped by the relay valve until air start control valve (1) is activated. The air from air start control valve goes to piston (10) behind pinion (8) for the starting motor. The air pressure on piston (10) puts piston spring (11) in compression and puts pinion (8) in engagement with the flywheel gear. When the pinion is in engagement, air can go out through another line to relay valve. The air activates relay valve which opens the supply line to the air starting motor.

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

The air with lubrication goes into the air motor through air inlet (5). The pressure of the air pushes against vanes (6) in rotor (7), and then exhausts through the outlet. This turns the rotor which is connected by gears (9) and a drive shaft to starter pinion (8) which turns the engine flywheel.

When the engine starts running, the flywheel will start to turn faster than pinion (8). The pinion (8) retracts under this condition. This prevents damage to the motor, pinion (8) or flywheel gear.

When air start control valve (1) is released, the air pressure and flow to piston (10) behind pinion (8) is stopped, piston spring (11) retracts pinion (8). Relay valve (3) stops the flow of air to the air starting motor.

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