3408C, 3412C and 3412D High Performance Marine Engines Caterpillar

Illustration 1	g01027452
Right side view (1) Rack solenoid (Brushless Torque Motor)

Illustration 2	g01027458
Rear view (2) Personality module (3) Electronic Control Module (ECM)

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

The engine uses the following three types of electronic components:

• input component

• control component

• output component

An input component is one that sends an electrical signal to the Electronic Control Module (ECM) of the system. The signal that is sent varies in either of the following ways:

• voltage

• frequency

The ECM interprets the signal from the input component as information about the condition, environment, or operation of the engine.

A control component (ECM) receives the input signals from the input components. Electronic circuits inside the control component evaluate the signals from the input components. These electronic circuits also supply electrical energy to the output components of the system. The electrical energy that is supplied to the output components is based on predetermined combinations of input signal values.

An output component is one that is operated by a control module. The output component receives electrical energy from the control group. The output component uses that electrical energy in one of two ways. The output component can use that electrical energy in order to perform work. As an example, a moving solenoid plunger will perform work. The output component can use that electrical energy in order to provide information. As an example, a dash panel light or an alarm will provide information to the operator of the engine.

These electronic components provide the ability to electronically control the engine operation. Engines with electronic controls offer the following advantages:

• improvement in performance

• improvement in fuel consumption

• reduction in emissions levels

Various sensors feed engine data to the ECM. These sensors modify the following functions:

• boost pressure

• engine oil pressure

• engine speed

• fuel rack position

• throttle position

• on/off ignition

The ECM processes the data. Then, the ECM sends electronic signals to the fuel injection solenoids. The fuel injection solenoids move the fuel rack. This will optimize the efficiency and the performance of the engine.

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

• engine overspeed

• on board diagnostics

Data Link

A data link is used for the following items:

• Communicate the engine information.

• Communicate with Caterpillar electronic service tools.

• Calibrate the electronic engine control system.

• Troubleshoot the electronic engine control system.

• Program the electronic engine control system.

The electronic engine control system includes a data link. The data link communicates with other microprocessor based devices. These devices are compatible with SAE Recommended Practices J1708 and J1587. The data link can reduce the duplication of sensors by allowing the controls to share information.

The data link is used to communicate engine information to other electronic control systems. Also, the data link can interface with Caterpillar electronic service tools.

The data link monitors engine information. The engine information that is available on the data link includes the following information:

• boost pressure

• engine identification

• engine speed

• oil pressure

• rack position

• status and diagnostic information

• throttle position

The electronic service tools can be used to program the customer specified parameters. The tool is plugged into the data link connector. This allows the tool to communicate with the ECM. Also, the electronic service tools can be used to display the real time values of all the information that is available on the data link. This will help diagnose engine problems.

The electronic service tool is one method of programming the customer specified parameters that are selected by the customer.

System Diagnostic Codes

Refer to Electronic Troubleshooting Guide for a complete explanation of the Diagnostic Codes.

Electronic Control Module (ECM) And Personality Module

Illustration 3	g00354015
ECM and personality module (1) Electronic Control Module (ECM) (2) Fuel outlet (3) Fuel inlet (4) Personality module

The electronic engine control system uses an Electronic Control Module (ECM). The ECM is a microprocessor based device. The ECM is mounted on the top of the aftercooler housing. The ECM (1) and the personality module (4) are cooled by fuel. The fuel circulates through a manifold between two circuit boards in the control module. The fuel enters the control module from the fuel transfer pump. The fuel enters the control module through the fuel inlet (3). Then, the fuel exits the control module through the fuel outlet (2) .

The inputs and the outputs to the control module are designed to withstand the short circuits to the battery voltage without damage to the control. The electronic engine control system has the following features that are designed into the system.

• Resistance to radio frequency

• Resistance to electromagnetic interference

The system has passed tests for interference that is caused by two-way radios and by switching noise.

The ECM power supply provides electrical power to all engine mounted sensors and actuators. The following precautions have been designed into the ECM.

• reverse voltage polarity protection

• protection from voltage spikes or fluctuations

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

The ECM memory stores a selected factory engine rating. The memory also contains a personality module identification code. This code is used to avoid unauthorized tampering or switching of personality modules and other pertinent manufacturing information.

The wiring harness provides communications to the following areas:

• various sensors

• data link connector

• engine connectors

The Personality Module is attached to the ECM. The personality module provides all the instructions that are necessary for the ECM to function. The personality module contains the performance maps and the certification information for the engine. This certification information includes information on the fuel ratio and the rack control maps for a particular ratings group that utilizes common engine components.

The ECM is programmed to perform the following functions:

• diagnostic tests on all inputs

• diagnostic tests on all outputs

• identification of faulty circuits

Once a fault is detected, the fault can be displayed on a diagnostic lamp. The diagnostic code can be read by using an electronic service tool. A multimeter can be used to check most problems. Also, a multimeter can be used to troubleshoot most problems. The ECM will log the diagnostic codes that are generated during engine operation. These logged codes can be read by the electronic service tool.

Throttle Control Sensor

A throttle control sensor is used to interface with the throttle. The throttle control sensor's output signal is a Pulse Width Modulation (PWM) of constant frequency. Refer to Pulse Width Modulation in the Systems Operation, "Glossary of Electronic Control Terms". The PWM signal overcomes the serious errors that can result from analog signals. These errors occur from the following problems.

• current leakage between connector pins

• contamination in the wiring harness

• contamination in the connectors

The engine returns to low idle if the PWM signal is invalid due to an open wire or a shorted wire.

Fuel Rack Controls

Illustration 4	g00354016
Cross section view of the rack housing (1) Shutoff solenoid (2) Rack solenoid (BTM) (3) Fuel rack servo

Illustration 5	g00354018
Cross section view of rack position sensor (4) Fuel rack (5) Rack position sensor (6) Shutoff override shaft and lever assembly (manual shutoff)

Illustration 6	g00354019
Cross section view of engine speed sensor (7) Flywheel starter gear (8) Engine speed sensor

Engine oil pressure is used to move the fuel rack. An electronically actuated rack solenoid (BTM) (2) controls a double acting hydraulic servo. The servo directs engine oil pressure to either side of a piston that is connected to the fuel rack. The oil pressure moves the piston. The piston moves the fuel rack.

The servo is a rotor type oil pump. The servo increases the pressure of the engine oil that is supplied to the governor. The increased oil pressure allows a better regulation of engine speed during the rapid application or the removal of heavy loads on the engine.

The rack solenoid (BTM) (2) is installed in the side of the rack actuator housing on the fuel injection pump. The rack solenoid (BTM) (2) is controlled by the ECM. The lever of the rack solenoid (BTM) is engaged in a collar on the rack servo valve. The rack solenoid (BTM) is spring loaded toward the position of fuel off. The solenoid must receive a positive voltage in order to move to the position of fuel on.

Rack position sensor (5) is located inside the rack actuator housing. The rack position sensor is attached to the fuel rack by a magnet. The rack position sensor is a linear potentiometer that provides accurate feedback information for the ECM.

In addition to the rack position data, the ECM receives data from other sensors that are located in the rack actuator housing. The engine speed sensor (8) is triggered by radial slots on the flywheel. Oil pressure, inlet air pressure, and the boost pressure sensors are mounted on the engine. These sensors are connected to the ECM. The ECM will limit engine speed and power output of the engine if low oil pressure occurs. When there is a change in boost and/or inlet air pressure, the control module adjusts the quantity of fuel or the timing of fuel that is delivered to the engine.

The ECM operates shutoff solenoid (1). If the rack solenoid (BTM) (2) is unable to move the fuel rack to the position of fuel off, the shutoff solenoid will apply an additional force on the fuel rack in order to move the rack to the position of fuel off. A manual shutoff (6) (shutoff override shaft and lever assembly) is provided. The manual shutoff control shaft is spring loaded to a neutral position.

If the shutoff solenoid fails to energize, the solenoid override may be used to move the shutoff lever away from the fuel rack servo (3). This will allow the rack solenoid (BTM) to move the fuel rack even though the shutoff solenoid is not energized.

The manual shutoff may be used to shut down the engine when the shutoff solenoid energized and power is maintained to the ECM. The manual shutoff will be needed for some troubleshooting procedures.

The mechanical type of fuel ratio control, the torque control group, and various adjustment screws have been eliminated. The electronic control module performs all of these functions. The control module adjusts the engine power and the torque rise. This compensates for plugged air cleaners in order to limit the amount of smoke.

The amount of fuel that is needed by the engine to maintain a desired rpm is determined by the ECM. During a constant engine speed, the engine speed will decrease when an additional load is applied. The signal from the engine speed sensor (8) to the ECM changes. The control module identifies the change in the engine speed signal. The ECM then collects data from the other engine sensors. After the data is processed, the ECM will send a positive voltage to the rack solenoid.

The rack solenoid (BTM) moves the valve in fuel rack servo (3). This will cause the fuel rack to move 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 at a desired speed, the engine speed will increase when the load is decreased. The ECM receives the changed signal from the engine speed sensor (8). The ECM reduces the electrical signal that goes to the rack solenoid (BTM). The rack solenoid (BTM) moves the valve in the fuel rack servo (3). This will move the fuel rack 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.

During engine start-up, the electronic engine control system controls the start-up cycle. The throttle control is not needed. The ECM will automatically provide the engine with the correct amount of fuel that is required to start the engine. Since some oil pressure is required for the fuel rack servo to move the fuel rack, electronically controlled engines may require a slightly longer cranking time to start.

Governor Servo

Illustration 7	g00354021
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, the rack solenoid (BTM) moves valve (4) to the left. The valve opens oil outlet (B) and the valve closes oil passage (D). Pressure oil from oil inlet (A) pushes piston (1) and fuel rack (5) to the left. Oil that is behind the piston travels through oil passage (C), along valve (4), and exits through oil outlet (B).

Illustration 8	g00354022
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). This creates a hydraulic lock. The piston and the fuel rack movement is stopped.

Illustration 9	g00354023
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 larger on the left side. The area of the piston is smaller on the right side. The force of the oil is also greater on the left side of the piston. The piston and the fuel rack (5) moves to the right.