Systems Operation

Usage:

Introduction

Reference: For Specifications with illustrations, make reference to Specifications For 3412 Industrial Engine, SENR4651. If the Specifications in SENR4651 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.

Engine Design

Cylinder, Valve And Injection Pump Location

Number And Arrangement Of Cylinders ... 65 degree V-12

Valves Per Cylinder ... 4

Displacement ... 27.0 liters (1649 cu in)

Bore ... 137.2 mm (5.40 in)

Stroke ... 152.4 mm (6.00 in)

Compression ratio ... 14.5:1

Type Of Combustion ... Direct Injection

Direction Of Crankshaft Rotation (as viewed from flywheel end) ... Counterclockwise

Direction Of Fuel Pump Camshaft Rotation (as viewed from pump drive end) ... Counterclockwise

Firing Order (Injection Sequence) ... 1-4-9-8-5-2-11-10-3-6-7-12

Valve Lash Setting

Inlet ... 0.38 mm (.015 in)

Exhaust ... 0.76 mm (.030 in)

NOTE: Front end of engine is opposite the flywheel end. Left side and right side of engine are as viewed from the flywheel end. No. 1 cylinder is the front cylinder on the left side. No. 2 cylinder is the front cylinder on the right side.

Engine Information

Model Views

Right Hand Engine (right side view)

Right Hand Engine (left side view)

Right Hand Engine (front view)

Right Hand Engine (rear view)

The Caterpillar electronically controlled 3412 Industrial Engine has a 137 mm (5.40 in) bore, 152.4 mm (6.00 in) stroke. The engine is a four stroke cycle, 12 cylinder 65 degrees "V" shaped engine.

The engine is twin series turbocharged and jacket water aftercooled with direct fuel injection. The engine has a SAE No. "0" (zero) flywheel housing and dual viscous dampers. This engine is designed for either right or left hand service and to fit within a 1220 mm (48 in) width for oil well service-fracturing rig applications.

The electronic control system was designed to provided engine speed governing, automatic fuel ratio control, torque rise shaping and system diagnostics with data link.

Individual injection pumps and fuel lines, one for each cylinder, meter and pump fuel under high pressure to a fuel injection nozzle for each cylinder. A mechanical timing advance provides fuel injection timing over the full range of engine speed.

A full range electronic governor controls the fuel injection pump output to maintain the engine rpm, called for by the throttle position sensor.

The cooling system consists of a gear driven centrifugal pump, with two water temperature regulators which regulate the coolant temperature. A customer supplied fan drive and cooling system (radiator) is required.

The engine lubricating oil, which is both cooled and filtered, is supplied by a gear driven pump. Bypass valves provide unrestricted flow of lubrication oil to the engine parts when oil viscosity is high, or if either the engine oil cooler or the engine oil filter elements should become plugged.

Engine efficiency and engine performance depend on adherence to proper operation and maintenance recommendations, and the use of recommended fuels, coolants and lubrication oils.

Follow the recommended Maintenance Management Schedule with emphasis on air cleaner, oil, engine oil filter, fuel and fuel filter maintenance found in the Operation & Maintenance Manual.

Starting The Engine

The electronically controlled engine may need to crank slightly longer than a mechanically governed engine, because some oil pressure is required for the electronic actuator to move the rack. The check engine light should be ON while the engine is cranking, but should GO OUT, after engine oil pressure is achieved. At temperatures below 0°C (32°F), it may be necessary to spray starting fluid into the air cleaner inlet (follow the recommended procedure in the Operation & Maintenance Manual. If the engine fails to start in 30 seconds, allow the starting motor to cool for two minutes before trying it again.

Cold Mode Operation

The electronic control system automatically idles the engine at 900 to `000 rpm for the correct warm up time after a cold engine start [approximately less than 5°C (40°F)]. The electronic control system periodically checks the engine response and will reduce the idle speed down to 600 rpm when the engine is warmed.

After the engine is started and the cold mode operation is completed, the engine can be operated at low rpm and low power. The engine will reach normal operating temperature faster when operated at low rpm and low power demand than when idled at no load.

Shutoff Solenoid Override

A manual shutoff solenoid override lever is located on the side of the fuel pump. The engine can be shut off by rotating the manual shutoff lever in the counterclockwise (CCW) direction. Rotating the manual shutoff lever in the clockwise (CW) direction disables the shutoff solenoid.

If the solenoid has been disabled, the engine can be shut OFF by using the manual shutoff lever on the side of the fuel pump.

Show/hide table

DO NOT operate the engine without the rack actuator solenoid (BTM) in place and with the fuel shutoff solenoid disabled. Excessive engine speed may result.

Customer Specified Parameters

The electronic control system is capable of being programmed for several customer specified parameters. These parameters and a brief explanation of each are in the Operation & Maintenance Guide.

Glossary Of Electronic Control Terms

Actual Rack

The ECM's interpretation of the signal from the Rack Position Sensor, read as "Rack Pos" on the Caterpillar electronic service tools.

Actual Timing Advance

Degrees of advance beyond static (basic) timing.

Aftermarket Device

A device or accessory installed by the customer 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.

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.

Brushless Torque Motor (BTM)

Solenoid used to move fuel rack servo spool valve, also called rack solenoid.

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.

Coolant Temperature Sensor

Used to set Cold Mode and to trigger the shift out of Cold Mode during engine warmup.

Code

See Diagnostic Code.

Customer Specified Parameter

A Parameter that can be changed and whose value is set by the customer.

Data Link

An electrical connection for communication with other microprocessor based devices that are compatible with the American Trucking Association and SAE Standards. The Data Link is also the communication medium used for programming and troubleshooting with Caterpillar service tools.

Desired Rack Position ("Des Rack Pos" on Caterpillar service tools)

The rack setting calculated by the ECM as needed to attain or maintain the Desired RPM.

Desired RPM

An input to the electronic governor within the ECM, and the output signal from the engine control logic within the ECM. The engine control logic uses inputs from the Throttle Position Sensor, Engine Speed Sensor, Cold Mode, and Customer Parameters to determine "Desired RPM".

Desired Timing Advance ("Des Timing Adv" on Caterpillar service tools)

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

Diagnostic Code

Sometimes referred to as a "fault code", it is an indication of an existing problem in the electronic control system.

Diagnostic Lamp

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

Direct Current

The direction of current flow is consistently in one direction only.

Duty Cycle

Same as Pulse Width Modulation.

Electrically Erasable Programmable Read Only Memory (EEPROM)

A large scale integrated-circuit chip for storing digital data. It can be electronically erased and reprogrammed. Used to store electronic control system parameters that can be changed using the Caterpillar service tools.

Electronic Control Module (ECM)

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

Engine Speed Sensor

A magnetic sensor that measures engine speed from the rotation of the fuel injection pump camshaft (slotted retainer).

Estimated Dynamic Timing

Estimated actual injection timing. Calculated internally by the electronic control system.

Est Dyn Timing = Static Timing Spec + Actual Timing Advance + Port effect (.2 deg/100 rpm).

The ECM's estimate of actual injection timing.

Fuel-Air Ratio Control (FARC) or Fuel Ratio Control (FRC)

FRC rack - a rack limit based on fuel-to-air ratio, to limit emissions during acceleration. As the electronic control system senses a higher boost pressure (more air into the cylinder) it increases the FRC rack limit (allows more fuel into cylinder). It works much like the FRC on a mechanical governor.

FUEL OFF and FUEL ON

Refers to minimum fuel and maximum fuel positions of the fuel rack.

Harness

The wiring bundle connecting all components of the electronic control system.

Hertz (Hz)

Measure of frequency in cycles per second.

Inlet Air Pressure Sensor

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

Jacketwater Aftercooler (JWAC)

A means of cooling inlet air after the turbocharger, using jacket water for cooling. The inlet air is passed through an aftercooler (heat exchanger) before going to the inlet manifold.

Oil Pressure Sensor

This sensor measures engine oil pressure and sends a signal to the ECM.

Open Circuit

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

Parameter

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

Password

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

Personality Module or Ratings Personality Module

The module connected to the ECM which contains all the instructions (software) for the ECM, logged diagnostic codes, and performance maps for a specific horsepower family.

Programmable Read Only Memory (PROM)

A large scale integrated-circuit chip for storing digital data. It can be programmed only at the factory. Used in the electronic control system personality module to store control logic and rating information.

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").

Example of Pulse Width Modulation

Rated Rack Position: A limit on rack position which provides the specified horsepower and torque curves. This value comes from maps programmed into the personality module at the factory.
Rack Position Sensor: A linear position sensor which follows movement of the rack assembly and sends an electrical signal to the ECM.
Rack Solenoid (BTM): A rotary proportional solenoid [also called a Brushless Torque Motor (BTM)] used to move the fuel rack servo spool valve.
Reference Voltage: A regulated voltage supplied by the ECM to a sensor. The reference voltage is used by the sensor to generate a signal voltage.
Sensor: A device used to detect and convert a change in pressure, temperature, or mechanical movement into an electrical signal.
Service Program Module (SPM): A software program on a factory programmable computer chip, designed to adapt an Caterpillar service tool to a specific application.
Short Circuit: A condition where an electrical circuit is unintentionally connected to an undesirable point. Example: a wire which rubs against a component until it makes electrical contact.
Signal: A voltage or waveform used to transmit information, typically from a sensor to the ECM.
Speed "burp": A sudden brief change in engine speed.
Static Timing Specification: Fixed number of degrees determined by design of the fuel pump camshaft (determines injection timing with no advance). Note that the value displayed is the specification for static timing, NOT an electrically measured value.
Subsystem: As used here, it is a part of the electronic control system that relates to a particular function, for instance rack subsystem.
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 battery voltage supplied through the wiring harness.
'T' Harness: A test harness designed to permit normal circuit operation while measuring voltages, typically inserted between the two ends of a connector.
Throttle Position: The ECM's interpretation of the signal from the throttle position sensor.
Throttle Control Sensor: An electronic sensor which is connected to the throttle control and sends a Pulse Width Modulated Signal to the ECM.
Total Tattletale: Total number of changes to all customer specified parameters.
Transducer: A device that converts a mechanical signal to an electrical signal.
Transducer Module: A sealed unit mounted below the rack actuator housing and contains the engine Oil Pressure Sensor, Boost Pressure Sensor and protective signal conditioning circuitry.

Electronic Control System

Electronic Control System Components

Front View
(1) Personality module. (2) Electronic control module (ECM).

Right Side View
(3) Rack solenoid (BTM).

Left Side View
(4) Transducer module. (5) Shutoff solenoid.

The electronic control system is integrally designed into the engine fuel system to electronically control fuel delivery and injection timing.

Major components of the system are: ratings personality module (1), ECM (2), rack solenoid (BTM) (3), transducer module (4), shutoff solenoid (5), and several sensors.

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

An input component is one that sends an electrical signal to the main control module. The signal sent varies in either voltage or frequency in response to change in some specific system of the engine. The control module sees the input sensor signal as information about the condition, environment, or operation of the engine.

A control component is that component of the system that 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:

* Do work (such as move the fuel rack) and thereby take an active part in regulating or operating the engine.

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

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

The electronic control system is integrally designed into the engine fuel system to electronically control fuel delivery.

Various sensors feed engine data to the ECM. These sensors monitor boost pressure, engine oil pressure, engine speed, fuel rack position, throttle position, and on/off ignition. The ECM processes this data and sends electronic signals to the solenoids that move the fuel rack to optimize the efficiency and performance of the engine.

The electronic control system also has the following built-in functions:

* engine speed limiting

* on board diagnostics

A Data Link provided by the electronic control system is used to communicate engine information and to communicate with Caterpillar service tools to calibrate, troubleshoot and program the electronic control system.

Data Link

The electronic control system includes a Data Link intended for communication with other microprocessor based devices that are compatible with SAE Recommended Practices J1708 & J1587. The Data Link can reduce duplication of sensors by allowing controls to share information.

The Data Link is used to communicate engine information to other electronic control systems and to interface with Caterpillar service tools.

The engine information that is monitored on the Data Link include the following:

* Boost Pressure

* Customer Specified Parameters

* Engine Identification

* Engine Speed

* Oil Pressure

* Rack Position

* Status And Diagnostic Information

* Throttle Position

The Caterpillar service tools are used to program the customer specified parameters.

The Caterpillar service tools are one method of programming the customer specified parameters that are selected by a customer. The tool plugs into the Data Link Connector to communicate with the ECM. The Caterpillar service tools can be also be used to display real time values of all information available on the Data Link for diagnosing engine problems.

System Diagnostic Codes

For a complete explanation of the Diagnostic Codes, see Electronic Troubleshooting, 3412 Industrial Engine, SENR4646.

Electronic Control Module (ECM) And Personality Module

Electronic Control Module And Personality Module
(1) Personality Module. (2) Electronic Control Module (ECM) (cover removed).

Electronic Control Module
(3) Fuel outlet line. (4) Fuel inlet line.

The electronically controlled 3412 Industrial Engine uses a microprocessor based Electronic Control Module (ECM) which is isolation mounted on the top of the cylinder block. The (ECM) (2) 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 the fuel transfer pump, at fuel inlet line (4), and exits the control module at fuel outlet line (3).

All inputs and outputs to the control module are designed to tolerate short circuits to battery voltage or ground without damage to the control. Resistance to radio frequency and electro-magnetic interference are designed into the electronic control system. The system has passed tests for interference caused by two-way radios and switching noise.

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. In addition to acting as a power supply, the ECM also monitors all sensor inputs and provides the correct outputs to ensure desired engine operation.

The ECM contains memory to store customer specified parameters and identify a selected factory engine rating. This memory also contains a personality module identification code to deter unauthorized tampering or switching of personality modules and other pertinent manufacturing information.

The wiring harness provides communication or signal paths to the various sensors (boost sensor, throttle control sensor), the Data Link Connector, and the engine connectors.

The Personality Module (1), is attached to the ECM, and provides the instructions necessary for the ECM to perform its function. The Personality Module contains all the engine performance and certification information such as, fuel ratio and rated rack control maps for a particular ratings group that utilizes common engine components.

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 on a diagnostic lamp or the Diagnostic Code can be read using a service tool. A multimeter can be used to check or troubleshoot most problems. The ECM also will log or record most diagnostic codes generated during engine operation. These logged or intermittent codes can be read by the electronic service tool.

Throttle Control Sensor

A Throttle Control Sensor is used to eliminate the mechanical linkage between the engine and the throttle. The Throttle Control Sensor output is a constant frequency Pulse Width Modulation (PWM) signal rather than an analog voltage (refer to Pulse Width Modulation in glossary). 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 engine returns to Low Idle if the PWM signal is invalid due to a broken or shorted wire.

Transducer Module

Governor And Fuel Injection Pump Group

View A-A Transducer Module
(1) Transducer module. (2) Oil pressure sensor. (3) Inlet air pressure sensor. (4) Boost pressure.

The sealed transducer module is mounted opposite the rack actuator housing and contains an engine oil pressure sensor, inlet air pressure sensor, a boost pressure sensor and protective signal conditioning circuitry. Engine oil pressure is supplied to the fuel rack servo and oil pressure sensor by oil passages in the rack actuator center housing. A ceramic capacitive oil pressure transducer is used to limit engine speed if low oil pressure occurs. Boost pressure and air pressure upstream of the turbocharger are routed to the transducer module. Wiring for the rack position and engine speed signals are passed through the transducer module to minimize external connections.

Fuel Rack Controls

Governor And Fuel Injection Pump Group

View A-A Side View Of Transducer Module
(1) Oil pressure sensor. (2) Inlet air pressure sensor. (3) Boost pressure sensor.

View B-B Cross Section End View Of Rack Housing

View D-D Cross Section View Of Rack Housing
(4) Shutoff solenoid. (5) Rack solenoid (BTM). (6) Fuel rack servo.

View E-E Cross Section View Of Rack Position Sensor
(7) Fuel rack. (8) Rack position sensor. (9) Manual shutoff (shutoff override shaft and lever assembly).

View C-C Cross Section View Of Engine Speed Sensor
(10) Camshaft retainer. (11) Engine speed sensor.

Engine oil pressure is used to move the fuel rack. An electronically actuated rack solenoid (BTM) (5) controls a double acting hydraulic servo. The servo directs engine oil pressure to either side of a piston connected to the fuel rack which moves the piston and fuel rack.

The servo group is a gerotor-type oil pump used to boost the pressure of the engine oil supply to the governor up to a level that allows for satisfactory regulation of engine speed in order to recover from block loading and block load dump.

Rack solenoid (BTM) (5) is installed in the side of the rack actuator housing on the fuel injection pump and is controlled by the electronic control module. The lever of rack solenoid (BTM) (5) is engaged in a collar on the rack servo valve. Rack solenoid (BTM) (5) is spring loaded toward the "Fuel Off" position and must receive a positive voltage to move in the "Fuel On" direction.

Rack position sensor (8) is located inside the rack actuator housing and is attached to the fuel rack by a magnet. The rack position sensor is a linear potentiometer used for accurate feedback information for the electronic control module.

In addition to the rack position data, the electronic control module receives data from four other sensors located in the rack actuator housing and transducer module. The engine speed sensor (11) is triggered (signaled) by radial slots on the fuel injection pump camshaft retainer (10). The transducer module contains three sensors (1, 2, and 3) monitoring oil pressure, inlet air pressure, and the boost pressure. The electronic control module will limit engine speed and power output of the engine if low oil pressure occurs. The control module adjusts the quantity of fuel or the timings of fuel delivered to the engine when a change in boost and/or inlet air pressure is detected.

The electronic control module operates an energized to run shutoff solenoid (4). If rack solenoid (BTM) (5) is unable to move the fuel rack to the "Fuel Off" position, the shutoff solenoid (4) will apply an additional force on the fuel rack to move the rack to the "Fuel Off" position. A manually operated manual shutoff (9) is provided. The manual shutoff control shaft is spring loaded to a neutral position.

If the shutoff solenoid fails to energize, manual shutoff (9) may be used to move the shutoff lever away from the servo valve (6). This will allow rack solenoid (BTM) (5) to move the fuel rack even though the shutoff solenoid is not energized.

The manual shutoff (9) may be used to shut down the engine with the shutoff solenoid energized and power is maintained to the electronic control module. This method of shut down is used in some troubleshooting procedures.

The mechanical fuel ratio control, torque control group, and various adjustment screws have been eliminated. The electronic control module performs all of these functions. The control module adjusts engine power and torque rise to compensate for operating the engine at high altitudes or with plugged air cleaners, or to limit smoke.

The amount of fuel needed by the engine to maintain a desired rpm is determined by the electronic control module. With the engine running at a desired speed, the engine speed will decrease when an additional load is applied. The signal from engine speed sensor (11) to the electronic control module changes. The control module receives this signal and other data, processes all the data, and sends a positive voltage to rack solenoid (BTM) (5). Rack solenoid (BTM) (5) moves the valve in fuel rack servo (6) and the fuel rack moves in the "Fuel On" direction. The increase in fuel to the engine will increase engine speed. This action will continue until the engine is again running at the desired speed or until the rack position has increased up to a rack position limit.

With the engine running at a desired speed, the engine speed will increase when the load is decreased. The control module receives the changed signal from the engine speed sensor (11). The electronic control module reduces the electrical signal to rack solenoid (BTM) (5). Rack solenoid (BTM) (5) moves the valve in fuel rack servo (6), and the fuel rack moves in the "Fuel Off" direction. The decrease in fuel to the engine will decrease engine speed. This action will continue until the engine is again running at the desired speed.

With the electronic control system, when the engine is cranked to start there is no need to use the accelerator. The electronic control module will automatically provide the engine with the proper amount of fuel to start the engine. Since some oil pressure is required for the fuel rack servo to move the fuel rack, the 3412 Industrial Engine may require a slightly longer cranking time to start.

Governor Servo

Rack Movement Toward "Full Fuel"
(1) Piston. (2) Cylinder. (3) Sleeve. (4) Valve. (5) Fuel rack. (A) Oil inlet. (B) Oil outlet. (C) Oil passage. (D) Oil passage.

When the rack solenoid (BTM) is energized, it moves valve (4) to the left. The valve opens oil outlet (B) and closes oil passage (D). Pressure oil from oil inlet (A) pushes piston (1) and fuel rack (5) to the left. Oil behind the piston goes through oil passage (C), along valve (4) and out oil outlet (B).

No Rack Movement (Constant Engine Speed)
(1) Piston. (2) Cylinder. (3) Sleeve. (4) Valve. (5) Fuel Rack. (A) Oil inlet. (B) Oil outlet. (C) Oil passage. (D) Oil passage.

When the desired engine speed is reached, the rack solenoid (BTM) holds valve (4) in a fixed position. Piston (1) moves to the left until both oil outlet (B) and oil passage (D) are blocked by valve (4). Oil is trapped in the chamber behind piston (1) and creates a hydraulic lock which stops piston and fuel rack movement.

Rack Movement Toward "Fuel Off"
(1) Piston. (2) Cylinder. (3) Sleeve. (4) Valve. (5) Fuel rack. (A) Oil inlet. (B) Oil outlet. (C) Oil passage. (D) Oil passage.

When the rack solenoid (BTM) is de-energized, spring force in the solenoid moves valve (4) to the right. The valve closes oil outlet (B) and opens oil passage (D). Pressure oil from oil inlet (A) is now on both sides of piston (1). The area of the piston is greater on the left side than on the right side of the piston. The force of the oil is also greater on the left side of the piston and moves the piston and fuel rack (5) to the right.

Fuel System

Fuel Flow

Fuel System Schematic
(1) Secondary fuel filter base. (2) Fuel injection pump housing. (3) Pressure regulating valve. (4) Fuel injection line. (5) Fuel injection nozzle. (6) Fuel return line. (7) Electronic control module (ECM). (8) Fuel transfer pump. (9) Fuel priming pump. (10) Primary fuel filter. (11) Fuel tank.

As the engine is cranked and started, fuel transfer pump (8) pulls fuel from fuel tank (11) through primary fuel filter (10).

NOTE: When the engine has reached its normal operating temperature, inlet fuel temperature to transfer pump must not exceed 65°C (149°F). Fuel temperatures above 65°C (149°F) reduce the life of the electronics in the ECM and the transfer pump check valves. High fuel temperatures also reduce engine power output. Make sure fuel heaters are turned off in warm weather operating conditions.

From fuel transfer pump (8) the fuel is pushed through electronic control module (7) to keep the electric circuits cool. The cooling plate for the control module is a one piece die cast aluminum housing. Manifolds on top and bottom of the control module route fuel from the transfer pump through the cooling plate.

The fuel exits the electronic control module and flows through the secondary fuel filter to the fuel manifolds in fuel injection pump housing (2).

The fuel manifolds supply fuel for each fuel injection pump. Some of the fuel in the manifolds is constantly sent through a pressure regulating valve that connects the manifold to fuel return line (6). The pressure regulating valve controls the pressure in the manifolds and the amount of fuel that goes back to the fuel tank (11). The constant flow of fuel back to the tank removes air from the system.

Individual fuel injection lines carry fuel from the fuel injection pumps to each cylinder. One section of line connects between the fuel injection pump and an adapter on the valve cover base. Another section of line on the inside of the valve cover base connects between the adapter and the fuel injection nozzle.

The fuel transfer pump (8) is installed opposite the rotary servo pump on the end of the fuel injection pump. The fuel transfer pump has a pressure relief valve and a bypass valve. The pressure relief valve controls the maximum pressure of the fuel to the fuel injection pump housing. When the pressure gets too high, the relief valve open and directs the fuel back to the inlet side of the transfer pump. The bypass valve allows the fuel to go around the transfer pump gears when fuel priming pump is used.

When there is air on the inlet side of the system, the fuel priming pump is used, before the engine is started, to fill the low pressure side of the fuel system from the fuel tank. When the priming pump is used, movement of fuel through the low pressure side of the system removes air from the lines and components back into the fuel tank.

There is no bleed orifice or valve installed on the fuel injection pump housing to vent air from the high pressure part of the fuel system. Air trapped in the fuel injection lines can be vented by loosening all of the fuel injection line nuts where they connect to the adapters in the valve cover base. Move the governor lever to the low idle position. Crank the engine with the starting motor until fuel (without air) comes from the fuel line connections. Tighten the fuel line nuts. This procedure is necessary because the fuel priming pump will not create enough pressure to push fuel through the reverse flow check valves located in the fuel injection pump bonnets.

The injection pumps are in time with the engine and send fuel to the fuel injection nozzles under high pressure. When the fuel pressure at the fuel injection nozzle is high enough the fuel injection nozzle opens and sends fuel into the combustion chamber.

Fuel Injection Pump

Cross Section Of The Fuel Injection Pump Housing
(1) Fuel manifold. (2) Inlet passage. (3) Check valve. (4) Pressure relief passage. (5) Pump plunger. (6) Spring. (7) Gear. (8) Fuel rack (left). (9) Lifter. (10) Camshaft.

The rotation of the lobes on the camshaft (10) cause lifters (9) and pump plungers (5) to move up and down. The stroke of each pump plunger is always the same. The force of springs (6) hold lifters (9) against the cams of the camshaft.

The pump housing is a "V" shape (similar to the engine cylinder block), with six pumps on each side.

When the pump plunger is down, fuel from fuel manifold (1) goes through inlet passage (2) and fills the chamber above pump plunger (5). As the plunger moves up it closes the inlet passage.

The pressure of the fuel in the chamber above the plunger increases until it is high enough to cause check valve (3) to open. Fuel under high pressure flows out of the check valve, through the fuel line to the fuel injection nozzle, until the inlet passage opens into pressure relief passage (4) in the plunger. The pressure in the chamber decreases and check valve (3) closes.

The longer inlet passage (2) is closed, the larger the amount of fuel which will be forced through check valve (3). The period for which the inlet passage is closed is controlled by pressure relief passage (4). The design of the passage makes it possible to change the inlet passage closed time by rotation of the plunger. When the governor moves fuel racks (8), they move gears (7) that are fastened to plungers (5). This causes a rotation of the plungers.

Fuel Injection Nozzles

The fuel injection nozzle is installed in an adapter in the cylinder head and is extended into the combustion chamber. The fuel injection pump sends fuel with high pressure to the fuel injection nozzle where the fuel is made into a fine spray for good combustion.

Fuel Injection Nozzle
(1) Carbon dam. (2) Seal. (3) Passage. (4) Filter screen. (5) Inlet passage. (6) Orifice. (7) Valve. (8) Diameter. (9) Spring.

Seal (2) goes against the fuel injection nozzle adapter and prevents leakage of compression from the cylinder. Carbon dam (1) keeps carbon out of the bore in the fuel injection nozzle adapter.

Fuel with high pressure from the fuel injection pump goes into inlet passage (5). Fuel then goes through filter screen (4) and into passage (3) to the area below diameter (8) of valve (7). When the pressure of the fuel that pushes against diameter (8) becomes greater than the force of spring (9), valve (7) lifts up. This occurs when the fuel pressure goes above the Valve Opening Pressure of the fuel injection nozzle. When valve (7) lifts, the tip of the valve comes off of the fuel injection nozzle seat and the fuel will go through the six small orifices (6) into the combustion chamber.

The injection of fuel continues until the pressure of fuel against diameter (8) becomes less than the force of spring (9). With less pressure against diameter (8), spring (9) pushes valve (7) against the fuel injection nozzle seat and stops the flow of fuel to the combustion chamber.

NOTE: The fuel injection nozzle can not be disassembled and no adjustments can be made.

Air Inlet And Exhaust System

Air Inlet System And Exhaust System.
(1) Exhaust manifold. (2) Aftercooler. (3) High pressure turbocharger air inlet. (4) High pressure turbocharger compressor wheel. (5) High pressure turbocharger turbine wheel. (6) High pressure turbocharger exhaust outlet. (7) Low pressure turbocharger air inlet. (8) Low pressure turbocharger compressor wheel. (9) Low pressure turbocharger turbine wheel. (10) Low pressure turbocharger exhaust outlet.

The components of the air inlet and exhaust system control the quality and the amount of air available for combustion. There is an air cleaner, two turbochargers and exhaust manifold on each side of the engine.

A common aftercooler is located between the cylinder heads and toward the rear of the engine. The inlet manifold is a series of passages inside the cylinder block which connect the aftercooler to the inlet ports (passages) in the cylinder heads. A single camshaft, in the cylinder block, controls the movement of the valve system components.

Air flow is the same on both sides of the engine. Outside air enters the system through the air cleaners. Air is pulled through the low pressure turbocharger air inlet (7), compressed and heated by the low pressure turbocharger compressor wheel (8). The compressed air is then directed through pipe assembly to the high pressure turbocharger air inlet (3) of the high pressure turbocharger. After additional compression by the high pressure turbocharger compressor wheel (4) the air is forced into the aftercooler (2). The aftercooler (2) lowers the temperature of the compressed air before it enters the inlet manifold. This cooled compressed air passes through the inlet manifold and fills the inlet ports in the cylinder heads. Air flow from the inlet port into the cylinder is controlled by the inlet valves.

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

Exhaust gases from exhaust manifold (1) enter turbine side of the high pressure turbocharger and cause the high pressure turbocharger turbine wheel (5) to turn. The compressed gases from the high pressure turbocharger enter the turbine side of the low pressure turbocharger turbine wheel (9). The turbine wheels are connected to the shafts which drives the compressor wheels. Exhaust gases from the low pressure turbocharger pass through the low pressure turbocharger exhaust outlet (10).

Aftercooler

Aftercooler
(1) Aftercooler. (2) Pipe.

The aftercooler (1) cools the air coming out of the turbochargers before it goes into the inlet manifold. The aftercooler is located toward the rear of the engine between the cylinder heads. Coolant from the water pump flows into the aftercooler. It flows through the core assembly, then out of the aftercooler through a different pipe into the rear of the cylinder block. Inlet air from the compressor side of the turbochargers flows into the aftercooler through a pipe (2) on each side of the aftercooler housing. This lowers the temperature of the air to approximately 93°C (200°F). The cooler air goes out the bottom of the aftercooler into the inlet manifold. The purpose of this is to make the air going into the combustion chambers more dense. The more dense the air is, the more fuel the engine can burn efficiently. This gives the engine more power.

Turbocharger

Turbocharger
(1) Turbocharger. (2) Exhaust pipe. (3) Turbocharger.

There are two turbochargers (1) and (3) installed on each side of the engine. The first turbocharger (high pressure) on each side is connected to the exhaust manifold. Exhaust gases from the turbine side of first turbocharger are routed to the turbine side of the second turbocharger (low pressure). The exhaust are then expelled through exhaust pipe (2). The compressor side of the first turbocharger is connected to the compressor side of the second turbocharger by pipe assembly. The compressed air is then forced into the aftercooler housing.

Turbocharger
(4) Air inlet. (5) Compressor wheel. (6) Turbine wheel. (7) Exhaust outlet. (8) Compressor housing. (9) Oil inlet port. (10) Thrust collar. (11) Thrust bearing. (12) Turbine housing. (13) Spacer. (14) Air outlet. (15) Oil outlet port. (16) Bearing. (17) Lubrication passage. (18) Bearing. (19) Exhaust inlet.

The exhaust gases go through the blades of turbine wheel (6). This causes the turbine wheel and compressor wheel (5) to turn, which causes a compression of the inlet air.

When the load on the engine is increased, more fuel is put into the engine. This makes more exhaust gases and will cause the turbine and compressor wheels of the turbocharger to turn faster. As the turbocharger turns faster, it gives more inlet air and makes it possible for the engine to burn more fuel and will give the engine more power.

Maximum rpm of the turbocharger is controlled by the rack setting, the high idle speed setting and the height above sea level at which the engine is operated.

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NOTICE

If the high idle rpm or the rack setting is higher than given in the TMI (Technical Marketing Information), or Fuel Setting And Related Information Fiche (for the height above sea level at which the engine is operated), there can be damage to engine or turbocharger parts. Damage will result when increased heat and/or friction, due to the higher engine output, goes beyond the engine cooling and lubrication systems abilities.

Bearings (16 and 18) for the turbocharger use engine oil under pressure for lubrication. The oil comes in through the oil inlet port (9) and goes through lubrication passage (17) in the center section for lubrication of the bearings. Oil from the turbocharger goes out through the oil outlet port (15) in the bottom of the center section and goes back to the engine lubrication system.

The fuel rack adjustment is done at the factory for a specific engine application. The governor housing is sealed to prevent changes in the adjustment of the rack and the high idle speed setting.

Valve System Components

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

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

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

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

As the camshaft turns, the lobes of camshaft (9) cause lifters (8) to go up and down. This movement makes push rods (3) move inlet rocker arms (2). Movement of the rocker arms makes inlet bridges (1) move up and down on dowels mounted in the cylinder head. The bridges let one rocker arm open and close two valves (inlet or exhaust). There are two inlet and two exhaust valves for each cylinder.

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

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

Valve System Components
(1) Inlet bridge. (2) Inlet rocker arm. (7) Inlet valves. (10) Exhaust rocker arm. (11) Exhaust bridge. (12) Exhaust valves.

Lubrication System

Engine Oil Flow During Normal Operation
(1) Passage (to rocker arm shaft). (2) Passage (to idler gear in flywheel housing). (3) Passage (to gear bearings in flywheel housing). (4) Passage (to fuel injection pump housing and governor). (5) Rocker arm shaft. (6) Passage (to valve lifters). (7) Camshaft bearings. (8) Piston cooling tubes. (9) Passage (to timing gear housing). (10) Passage (to idler gear shaft). (11) Oil manifold. (12) Main bearings. (13) Oil supply line (to turbocharger). (14) Oil supply line (to manifold in cylinder block). (15) Engine oil filter bypass valve. (16) Engine oil cooler bypass valve. (17) Turbocharger. (18) Engine oil cooler. (19) Oil return line (from turbocharger). (20) Engine oil filters. (21) Oil pan. (22) Engine oil pump.

Oil Flow Through The Engine Oil Cooler, Engine Oil Filters And The Engine

Oil Lines And Filters
(15) Engine oil filter bypass valve. (16) Engine oil cooler bypass valve. (18) Engine oil cooler. (20) Engine oil filters. (23) Bypass valve body.

When the engine is in operation and the temperature of the oil is normal, engine oil pump (22) sends oil through bypass valve body (23), engine oil cooler (18) and engine oil filters (20) to oil manifold (11). From oil manifold (11) in right side of the cylinder block, oil is sent to the left oil manifold through drilled passages in the cylinder block that connect main bearings (12) and camshaft bearings (7). Oil goes through drilled holes in the crankshaft to give lubrication to the connecting rod bearings. A small amount of oil is sent through piston cooling tubes (8) to make the pistons cooler. Oil goes through grooves in the bores for the front and rear camshaft bearings and then into passages (6) that connect the valve lifter bores.

Oil is sent through passages (1), on front and rear, to rocker arm shafts (5) on both cylinder heads. Holes in rocker arm shafts (5) let the oil give lubrication to the valve system components in the cylinder head.

The fuel injection pump and governor gets oil from passage (4) in the cylinder block. There is a small gear pump between the injection pump housing and the governor. This pump sends oil under pressure to the fuel injection pump and governor.

The idler gear bores get oil from passages (10) in the cylinder block, oil then goes through the shaft for the bearings of the idler gears installed on the front and rear of the cylinder block.

The idler gear bearings get oil under pressure through passage (2). The driven gear bearings get oil under pressure through passage (3).

Pressure oil is sent to the turbocharger bearings through external oil supply line (13). The oil goes out of turbocharger (17) back to oil pan (21) through oil return line (19).

There is a bypass valve in the engine oil pump. This bypass valve controls the maximum pressure of the oil from the engine oil pump. The engine oil pump can put more oil into the system than is needed. When there is more oil than needed, the oil pressure goes up and the bypass valve will open. This allows the oil that is not needed to go back to the inlet oil passage of the engine oil pump.

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

Lubrication System Components
(11) Oil manifold. (13) Oil supply line (to turbocharger). (18) Engine oil cooler. (19) Oil return line (from turbocharger). (20) Engine oil filters. (21) Oil pan.

When the engine is cold (starting condition), engine oil filter bypass valve (15) and engine oil cooler bypass valve (16) open because cold oil with high viscosity causes a restriction to the oil flow through engine oil cooler (18) and engine oil filters (20). With the bypass valves open, oil flows directly from the engine oil pump to oil manifold (11). This will give immediate lubrication to all components until the engine becomes warm.

When the oil gets warm, the pressure difference in the engine oil filter bypass valve (15) and engine oil cooler bypass valve (16) decreases and the bypass valves close. Now there is a normal flow through engine oil cooler (18) and engine oil filters (20).

The bypass valves will also open when there is a restriction in the engine oil cooler or engine oil filter. This action does not let an engine oil cooler or engine oil filter with a restriction prevent the lubrication of the engine.

Cooling System

Cooling System Schematic
(1) Aftercooler. (2) Pipe. (3) Temperature regulator housing. (4) To radiator. (5) Engine oil cooler. (6) Transmission oil cooler. (7) Water pump inlet. (8) Return from radiator. (9) Bypass lines.

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

Cooling system
(2) Pipe (to aftercooler). (7) Water pump inlet. (9) Bypass lines. (10) Outlet pipes. (11) Water pump.

(5) Engine oil cooler. (6) Transmission oil cooler. (12) Bonnet.

The water pump (11) forces coolant out in three directions. Part of it flows through pipe (2) to aftercooler (1). The coolant goes through the aftercooler core and enters into the cylinder block at the top rear. Part of the coolant flows through the engine oil cooler (5) and into the side of the cylinder block. Part of the coolant flows through transmission oil cooler (6), bonnet (12) and enters into the side of the cylinder block with the flow from the engine oil cooler.

In normal operation (engine warm), water pump (11) sends coolant through engine oil cooler (5), transmission oil cooler (6) and aftercooler (1) and then into the cylinder block.

Coolant moves through the cylinder block to both cylinder heads, and then goes to the temperature regulator housings (3). The temperature regulators are open and most of the coolant goes through the outlet pipes (10) to the radiator. The coolant is made cooler as it moves through the radiator. When the coolant gets to the bottom of the radiator. it goes to water pump inlet (7).

NOTE: The water temperature regulator is an important part of the cooling system. It divides coolant flow between the radiator and radiator bypass lines (9) as necessary to maintain the correct temperature. If the water temperature regulator is not installed in the system, there is no mechanical control, and most of the coolant will take the path of least resistance through the bypass. This will cause the engine to overheat in hot weather. In cold weather, even the small amount of coolant that goes through the radiator is too much, and the engine will not get to normal operation temperatures.

When the engine is cold, the water temperature regulators are closed, and the coolant is stopped from going to the radiator. The coolant goes from the temperature regulator housing (3) back to the water pump (11) through radiator bypass lines (9).

Coolant Conditioner

Some conditions of operation have been found to cause pitting (small holes in the metal surface) from corrosion or cavitation erosion (wear caused by air bubbles in the coolant) on the outer surface of the cylinder liners and the inner surface of the cylinder 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 elements, similar to the fuel filter and engine oil filter elements, fasten to a base that is mounted on the engine or is remote mounted. Coolant flows through lines from the water pump to the base and back to the block. There is a constant flow of coolant through the 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 dry material, dissolves (goes into solution) and mixes to the correct concentration. Two basic types of elements are used for the cooling system, and they are called the "Precharge" and the "Maintenance" elements. Each type of element has a specific use and must be used correctly to get the necessary concentration for cooling system protection. The elements also contain a filter and should be left in the system so coolant flows through it after the conditioner material is dissolved.

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

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

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NOTICE

Do not use any Methoxy Propanol/Based Antifreezes or coolant in the Cooling System. Methoxy Propanol will cause some seals and gaskets to deteriorate and fail. Do not use Dowtherm 209 Full-Fill in a cooling system that has a coolant conditioner. These two systems are not compatible (corrosion inhibitor is reduced) when used together.

Basic Block

Cylinder Block, Liners And Heads

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

The cylinder liners can be removed for replacement. The top surface of the block is the seat for the cylinder liner flange. Engine coolant flows around the liners to keep them cool. Three O-ring seals around the bottom of the liner make a seal between the liner and the block. A filler band at the top of each liner forms a seal between the liner and the cylinder block.

The engine has a single, cast head on each side. Four vertical valves (two inlet and two exhaust), controlled by a pushrod valve system, are used per each cylinder. The opening for the fuel injection nozzles in each cylinder is located between the four valves. Series ports (passages) are used for both inlet and exhaust valves.

A steel spacer plate is used between the cylinder head and block. A thin gasket is used between the plate and the block to seal water and oil. A thick gasket of metal and asbestos is used between the plate and the head to seal combustion gases, water and oil.

The size of the pushrod openings through the head permits the removal of the valve lifters with the head installed.

Valve guides without shoulders are pressed into the cylinder head.

Pistons, Rings And Connecting Rods

Piston Assembly
(1) Crown assembly. (2) Skirt assembly. (3) Piston pin. (4) Retainer ring.

The piston assembly is of a two piece articulated design. The crown assembly is held in position in the piston skirt by a piston pin. The piston pins are held in place by two snap rings that fit in the grooves in the pin bore of the pistons. The connecting rod has a taper on the pin bore end.

The aluminum pistons have three rings; two compression rings and one oil ring. All rings are located above the piston pin bore. The compression rings are of the KEYSTONE type, which has a tapered shape. The action of these rings in the piston groove, which is also tapered, helps prevent ring seizure caused by too many carbon deposits. The oil control ring is of the standard (conventional) type. The seat for the rings is an iron band that is cast into the piston. Oil returns to the crankcase through holes in the oil ring groove.

Piston cooling tubes, located on the cylinder block main webs, direct oil to cool and give lubrication to the piston pins and cylinder walls.

Crankshaft

The crankshaft changes the combustion forces in the cylinder into usable rotating torque which powers the machine. Vibration, caused by combustion impacts along the crankshaft, is kept small by a vibration damper on the front of the crankshaft.

There is a gear at the front of the crankshaft to drive the timing gears and the engine oil pump. Seals and wear sleeves are used at both ends of the crankshaft for easy replacement and a reduction of maintenance cost. Pressure oil is supplied to all bearing surfaces through drilled holes in the crankshaft. The crankshaft is supported by seven main bearings. A thrust plate at either side of the center main bearing controls the end play of the crankshaft.

Camshaft

The engine has a single camshaft that is driven at the front end. It is supported by seven bearings. As the camshaft turns, each cam (lobe) (through the action of valve systems components) moves a roller follower, which in turn moves a push rod and two valves (either exhaust or inlet) for each cylinder. The camshaft gear must be timed to the crankshaft gear. The relation of the cam (lobes) to the camshaft gear cause the valves in each cylinder to open and close at the correct time.

A gear on the rear of the camshaft is used to drive the balance gear and any accessory equipment mounted on the rear of the engine.

Vibration Damper

The twisting of the crankshaft, due to the regular power impacts along its length, is called twisting (torsional) vibration. The viscous (fluid type) vibration dampers are installed on the front end of the crankshaft. They are used for reduction of torsional vibrations and stops the vibration from building up to amounts that cause damage.

Electrical System

One thing different about the Caterpillar electronic control system is that more of the input components are electronic. These components require an operating voltage, and often times a reference voltage as well.

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

For schematics of the electronic control system, see Electrical Schematics, SENR4657.

Electronic Control Module Power Circuit

The design of the electronic circuits inside the Electronic Control Module (ECM) are such that the ordinary switch input circuits to the ECM have a tolerance for resistance and shorts between wires. These tolerances are as follows:

1. Electronic Control System will tolerate resistance in any ordinary switch up to 2.5 Ohms without malfunctioning.

2. Electronic control system will tolerate shorts to ground or between wires in any ordinary switch input down to 5,000 Ohms without malfunctioning.

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NOTICE

The +12 Volt wire in the data link harness of the ECM is provided to power the electronic control system service tools only. No other devices should be powered by this wire. The ECM was not designed to carry high current loads and is not short circuit protected.

The ECM draws a maximum of 6.5 Amps at 12 Volts from the electrical system under steady state conditions. The ECM will draw a maximum of 9 Amps on engine start-up. However, the electronic control system will function with less than 12 Volts. A minimum of 9 Volts is required while cranking, and 11 Volts 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 0.5 Volt of frame ground.

Electronic control system is protected against power surges on the 12 Volt power supply due to alternator load dumps, etc. and for jump starting with voltages up to 28 Volts.

Engine Speed Input Circuit

Engine speed is sensed by an electronic engine speed sensor. It is similar to electro-magnetic pickups with which you may already be familiar; that is, the signal is generated by placing the sensor near a rotating component, but it is different in that it requires an operating voltage. The engine speed sensor is provided an operating voltage of 8.0 ± 0.4 Volts by the ECM.

The output of the engine speed sensor is a voltage pulse whose frequency is dependent on the speed of the engine. The frequency of the pulse is interpreted by the ECM as engine speed. Typically the frequency of this signal is 10 to 50 Hz (Hertz) while cranking, and approximately 120 Hz at low idle.

Fuel Rack Input Circuit

The engine fuel rack signal is obtained from an electronic linear position sensor which follows the movement of the rack assembly. This sensor requires an operating voltage of 8.0 ± 0.4 Volts, and a reference voltage of 5.0 ± 0.25 Volts. These voltages are provided by the ECM.

The output of the rack position sensor is a voltage between 0.3 and 5.25 Volts. This voltage is dependent upon the position of the rack position sensor, and is interpreted by the ECM as rack position.

Engine Coolant Temperature Circuit

Engine coolant temperature is obtained from an electronic sensor. It is mounted on the engine and its data is sent to the ECM via the engine wiring harness. This sensor requires an operating voltage of 8V ± 0.4V and operates at a temperature range between 40 to 120°C (104 to 248°F).

The output of the coolant temperature sensor is a voltage between 0.5V and 4.5V at the previously stated input range. This voltage is dependent upon the engine coolant temperature, and is interpreted by the ECM as the coolant temperature.

Inlet Air Pressure Input Circuit

The inlet air pressure sensor is located in the transducer module. Inlet air pressure, taken before the turbocharger and after the air cleaner, is routed to this sensor. The transducer requires an operating voltage of 8.0 ± 0.4 Volts, and a reference voltage of 5.0 ± 0.25 Volts.

The output of the inlet air pressure sensor is a DC voltage between 1.0 and 5.0 Volts. This voltage is dependent upon the pressure felt by the inlet air pressure sensor, and is interpreted by the ECM as inlet air pressure (absolute).

Boost Pressure Input Circuit

The boost pressure sensor is also located in the transducer module. Air from the engine inlet manifold is routed to this sensor. The same operating and reference volrages provided to the inlet air pressure sensor are provided to this sensor.

The output of the boost pressure sensor is a DC voltage of 1.0 to 5.0 Volts. This voltage is dependent upon the pressure felt by the boost pressure sensor, and is interpreted by the ECM as engine boost pressure (indicator).

Engine Oil Pressure Input Circuit

The engine oil pressure sensor is also located in the transducer module. Engine oil pressure from the fuel injection pump is routed to this sensor. This sensor also requires an operating voltage of 8 Volts, and a reference voltage of 5 Volts.

The output of the oil pressure sensor is a DC voltage of 1.8 to 5.3 Volts. This voltage is dependent upon engine oil pressure and is interpreted by the ECM as oil pressure.

The engine oil pressure sensor is designed to measure oil pressure between 0 and 312 kPa (45 psi). Engine oil pressures greater than 312 kPa (45 psi) are read as 312 kPa (45 psi). This limited oil pressure reading range provides more accurate low oil pressure readings (where oil pressure readings are most important) than a sensor capable of reading the maximum engine oil pressure.

Throttle Control Input Circuit

Throttle position is obtained from an electronic sensor. An operating volrage of 24 Volts is provided to the sensor by the electrical system.

The output of the throttle position sensor is a constant frequency pulsed voltage of 0 to 5.25 Volts. The pulse width, not the frequency, of the signal is dependent upon the position of the throttle position sensor and is interpreted by the ECM as throttle position. Output pulse width is from 22 percent to 78 percent and is rescaled by the ECM as a throttle position of 0 percent to 100 percent.

Shutoff Solenoid Output Circuit

The shutoff solenoid is an output component of electronic control system that must be energized for the engine to run.

The output of the ECM module to the shutoff solenoid is a pulsed voltage that can reach up to 6 Volts for about one-half second after the power switch(es) is turned ON for the purpose of pulling in the solenoid, and then drops off to approximately 1 Volt to hold the solenoid in.

The electronic control system is designed to continue operation of the engine with as many faults as possible. There are four conditions which will deenergize the shutoff solenoid and shut down the engine. These are as follows:

1. Loss of engine speed signal.

2. An engine speed signal of 2300 rpm or greater.

3. A defective shutoff solenoid.

4. Loss of electrical power to the electronic control system control module.

Fuel Rack Output Circuit

Movement of the engine fuel rack is accomplished by electronic control system with a new type of output component known as a rotary solenoid (BTM).

A rotary solenoid (BTM) is a device whose movement is proportional to the electrical current flowing through it. The ECM provides a pulsed voltage of 0.0 to 3.6 Volts to the rotary solenoid (BTM).

The rotary solenoid (rack solenoid) moves the engine fuel rack through the movement of the governor servo spool valve and hydraulic pressure.

The electronic control system has a built-in operational test for the rack solenoid (BTM). This test is accomplished as follows:

1. Remove the rack solenoid (BTM) from its housing.

2. Position it so that the arm of the solenoid is free to move.

3. Turn the power switch(es) ON.

The expected results of this test are that after about 5 seconds the solenoid arm will sweep to the full ON position, remain there a few seconds, and then sweep back to the OFF position. Sweep time will be about 5 seconds in both directions.

Check Engine Light Output Circuit

The data link harness provides information about the electronic control system to the check engine light. The light is ON when the power switch(es) is ON and the engine is not running to verify that the lamp is working, and should go out when the engine has been started and proper engine oil pressure is reached, If the light does not go out shortly after starting the engine it is an indication of either low oil pressure, or a electronic control system fault has been detected.

An operating voltage of 12 Volts is provided to the check engine light by the electrical system. The ECM grounds the light to turn it on.

Engine Electrical System

The engine electrical system has two circuits: the charging circuit, and the low amperage circuit. Some of the electrical system components are used in more than one circuit. The battery (batteries), disconnect switch, 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.

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NOTICE

The disconnect switch, if so equipped, must be in the ON position to let the electrical system function. There will be damage to some of the charging circuit components if the engine is running with the disconnect switch in the OFF position.

The low amperage circuit and the charging circuit are both connected through the ammeter.

Charging System Components

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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.

Alternator (3T1888)

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

The alternator is driven by V-belts 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.

Most of this current goes to charge the battery and to supply the low amperage circuit, and the remainder is sent 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.

Alternator (6T7223)

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

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

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 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.

Regulator

Alternator (9G9538)

The alternator is driven by V-belts from the crankshaft pulley. The Nippondenso alternator has three-phase, full-wave rectified output. It is brushless. The rotor and bearings are the only moving parts. The regulator is part of the alternator.

Alternator
(1) Fan. (2) Front frame assembly. (3) Stator assembly. (4) Rotor assembly. (5) Field winding (coil assembly). (6) Regulator assembly. (7) Condenser (suppression capacitor). (8) Rectifier assembly. (9) Rear frame assembly.

When the engine is started and the rotor turns inside the stator windings, three-phase alternating current (AC) and rapidly rising voltage is generated.

A small amount of alternating current (AC) is changed (rectified) to pulsating direct current (DC) by the exciter diodes on the rectifier assembly. Output current from these diodes adds to the initial current which flows through the rotor field windings from residual magnetism. This will make the rotor a stronger magnet and cause the alternator to become activated automatically. As rotor speed, current and voltages increase, the rotor field current increases enough until the alternator becomes fully activated.

The main battery charging current is charged (rectified) from AC to DC by the other positive and negative diodes in the rectifier and pack (main output diodes) which operate in a full wave linkage rectifier circuit.

Alternator output is controlled by a regulator, which is inside the alternator rear frame.

Regulator

The regulator is fastened to the alternator by two different methods. One method fastens the regulator to the top, rear of alternator. With the other method the regulator is fastened separately by use of a wire and a connector that goes into the alternator.

The voltage regulator is a solid state (transistor, no moving parts) electronic switch. It feels the voltage in the system and gives the necessary field current (current to the field windings of the alternator) for the alternator to make the needed voltage. The voltage regulator controls the field current to the alternator by switching on and off many times a second. There is no voltage adjustment for this regulator.