3406C (PEEC III) Truck Engines Caterpillar

Illustration 1	g00527842
Electrical components of the PEEC III System (1) Timing solenoid (2) Rack solenoid (3) Electronic Control Module (ECM) (4) Coolant sensor (5) Transducer module (6) Ratings personality module

The Programmable Electronic Engine Control III System (PEEC III) is integrally designed into the engine fuel system to electronically control the fuel delivery and the injection timing.

The following components are the major components of the PEEC III system:

• Timing Solenoid (BTM) (1)

• Rack Solenoid (BTM) (2)

• Ratings Personality Module (6)

• Transducer Module (5)

• ECM (3)

• Vehicle Speed Buffer

• several sensors

The PEEC III system uses three types of components:

• input

• control

• output

An input component is a component that sends an electrical signal to the electronic control module of the system. The signal varies in either voltage or in frequency in response to a change in some specific system of the vehicle. The electronic control module sees the input sensor signal as information about the following items:

• the condition of the engine

• the environment of the engine

• the operation of the engine

A control component receives the input signals. Electronic circuits that are inside the control evaluate the signals. The electronic circuits supply the electrical energy to the output components of the system. The supply of electrical energy is in response to the preset combinations of input signal values.

An output component is a component that is operated by a control module. The output component receives electrical energy from the control group. The electrical energy is used to accomplish one of the following tasks:

• The electrical energy can perform work so that the energy helps in regulating or in operating the vehicle.

• The electrical energy can provide information or a warning to the operator of the vehicle or to another person.

These components provide the ability to electronically control the engine operation in order to achieve the following tasks:

• improved performance

• improved fuel economy

• improved driveability

• reduced level of emissions

PEEC III System

The PEEC III 3406C Diesel Truck Engine is an electronically controlled 3406C. The PEEC III system controls the fuel rate and the timing electronically. The PEEC III system does not use flyweights and linkages. The electronics also replace the following components:

• mechanical fuel air ratio control

• torque control group

• various adjustment screws

PEEC III uses several sensors as inputs to control two basic functions:

• rack position

• timing position

The operation of each of these solenoids is similar. The PEEC III system calculates the correct position of the rack and the correct timing advance. The PEEC III system then varies the voltage to the solenoid (BTM) in order to move the rack or the timing advance to the desired position. Position sensors tell the PEEC III system when the rack or the timing is at the desired position.

Electronic Controls

The electronic controller consists of two main components:

• Electronic Control Module (ECM)

• Personality Module

The ECM is the computer which controls the PEEC III engine. The personality module is the software which controls the computer's behavior. The two must be used together. Neither component can function alone.

Rack Controls

The rack mechanism on a PEEC III engine is very similar to a mechanical 3406C engine. The fuel injection pump is nearly identical. The rack is moved by a servo valve which receives oil pressure from the fuel injection pump. However, the PEEC III servo spool is moved by a solenoid (BTM) rather than by a linkage that is controlled by flyweights and springs. The PEEC III system comes up with a desired rpm that is based on the following information:

• throttle position

• vehicle speed

• customer specified parameters

• certain diagnostic codes

The PEEC III system senses the actual engine speed by using the engine speed sensor. The PEEC III system controls the rack in order to achieve the desired rpm that is based on the previous criteria.

Illustration 2	g00536038
PEEC III RPM Control Logic (A) Cruise control/PTO logic (B) Cruise control/PTO control (C) Engine control logic (D) Throttle position sensor (E) Cold mode operation (F) Customer parameters (1) Cruise control set mph/pto set rpm (2) Clutch switch (3) Brake switch (4) Cruise control ON/OFF switch (5) Set/resume switch (6) Vehicle speed (7) Engine rpm (8) Desired rpm (9) Throttle position (10) Coolant temperature

The PEEC III system adjusts the voltage to the rack solenoid (BTM). More voltage results in more rack. Less voltage results in less rack. The PEEC III system senses the movement of the rack by reading the rack position sensor. The PEEC III system regulates the voltage to the rack solenoid until the rack is in the desired position.

Illustration 3	g00536039
PEEC III Electronic Governor (G) Rack position sensor (H) Rack control (I) Electronic governor (J) Rack Solenoid (K) Rack control map (L) Torque maps (M) Engine speed sensor (N) Transducer module (7) Engine rpm (8) Desired rpm (11) Actual rack position (12) Desired rack position (13) Signal to rack solenoid (14) FRC limit (15) Rated rack limit (16) Boost pressure

The PEEC III system sets certain limits on rack motion. The FRC rack is a rack limit. The FRC is based on the fuel air ratio control for emission purposes. The FRC rack works in a similar way as the mechanical engine's fuel air ratio control. When the PEEC III system senses a higher boost pressure (more air into cylinder), the ECM increases the FRC rack limit which allows more fuel into the cylinder. The rated rack is a rack limit that is based on the horsepower of the engine. The rated rack is similar to the rack stops and the torque springs on a mechanical engine. The rated rack provides the horsepower and the torque curves for a specific engine that is programmed by the factory into the personality module.

Timing Advance Controls

The timing advance mechanism is similar to the timing advance mechanism that is used on the 3406C mechanical engine. A timing solenoid (BTM) is used to control the timing advance instead of using flyweights. The PEEC III system adjusts the voltage to the timing solenoid in order to change the timing advance. More voltage results in more timing advance. Less voltage results in less timing advance. The timing position sensor informs the PEEC III system on the amount of timing advance. The PEEC III system adjusts the voltage to the timing solenoid until the timing advance is in the desired position.

Illustration 4	g00536041
PEEC III Timing Advance (A) Timing control (B) Timing maps (C) Timing solenoid (D) Throttle position sensor (1) Desired timing advance (2) Signal to timing solenoid (3) Actual timing advance (4) Cold mode operation (5) Rack position (6) Engine rpm

Programmable Parameters

Certain parameters that affect the PEEC III 3406C Diesel Truck Engine operation may be changed with electronic service tools (either the ECAP or DDT). The parameters are stored in the ECM. The parameters are protected from unauthorized changes by passwords. These parameters are either system configuration parameters or customer parameters. System configuration parameters affect the horsepower family or the emissions. Customer parameters are the following parameters:

• cruise control limits

• vehicle speed limits

• progressive shifting

• horsepower rating within a family

• PTO operation

Some parameters may affect the engine operation. These parameters may lead to power or to performance complaints although the engine is running correctly with the given parameters.

Passwords

System Configuration Parameters are protected by factory passwords. Factory passwords are calculated on a computer system. The computer system is only available to Caterpillar dealers. Since factory passwords contain alphabetic characters, only the ECAP may change System Configuration Parameters. Customer Parameters are protected by customer passwords. The customer passwords are programmed by the customer. Either the ECAP or the DDT service tool may change the customer parameters.

Note: If the password contains alphabetic characters, only the ECAP can change the password.

Diagnostics

The PEEC III electronics have some ability to diagnose problems. When a problem is detected, a diagnostic code is generated and the diagnostic lamp is turned on. In most cases, the code is also stored in permanent memory in the ECM. Codes that represent current faults are called active codes. Active codes indicate that a problem of some kind currently exists. Active codes should be investigated and the active codes should be corrected as soon as possible. Refer to Troubleshooting, SENR5503, "Troubleshooting Diagnostic Codes" for more information on troubleshooting diagnostic codes. Codes that are stored in memory are called logged codes. The problem may have been temporary. The problem may have been repaired. Logged codes are not always problems. Logged codes are meant to be an indicator of probable causes for intermittent problems. In addition, some logged codes record events rather than failures. Some codes do not require passwords to clear the codes. These codes are deleted after 100 ECM hours. Refer to Troubleshooting, SENR5503, "Troubleshooting Diagnostic Codes" for more details.

Illustration 5	g00826129
(1) Shutoff solenoid (2) Rack position sensor (3) Engine Data Link connector (4) Rack solenoid (5) Engine speed sensor (6) Transducer module (7) ECM (8) Ground stud on the engine block (9) Coolant temperature sensor (10) Timing solenoid (11) Timing position sensor (12) Vehicle speed sensor (13) Vehicle speed buffer (14) Dash Data Link (15) Throttle position sensor (16) Negative ground through starter or main frame rail (17) Coolant level sensor (18) Diagnostic lamp (19) Warning lamp (20) Clutch switch (21) Brake switch (22) Parking brake switch (23) Cruise control ON/OFF switch (24) Cruise control SET/RESUME switch (25) Battery (26) OEM vehicle wiring harness

Data Link

The PEEC III system includes a Data Link that is intended for communication with other microprocessor based devices that are compatible with the SAE J1708 and SAE J1587. The Data Link can reduce duplication of truck sensors by allowing controls to share information. The Data Link is used to communicate engine information to other electronic vehicle control systems. The Data Link is also used to interface with the following Caterpillar service tools:

• Electronic Control Analyzer Programmer (ECAP)

• Digital Diagnostic Tool (DDT)

The Data Link contains the following information:

• Boost Pressure

• Customer Specified Parameters

• Engine Identification

• Engine Speed

• Oil Pressure

• Rack Position

• Status And Diagnostic Information

• Throttle Position

• Vehicle Speed

• Coolant Temperature

• Coolant Level

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

One method of programming the customer specified parameters uses the Electronic Control Analyzer Programmer (ECAP). The ECAP plugs into the Data Link connector in order to communicate with the ECM. The ECAP can also display the real time values of all the information that is available on the Data Link for diagnosing engine problems.

Programming of the customer specified parameters can be password protected in order to prevent unauthorized tampering or changing of the customer selected values. With the proper customer passwords, changing of limits of the following parameters is easily accomplished.

• Low Gears No. 1 RPM Limit (LOGR No. 1)

• Vehicle Speed Limit (VSL)

• Low Cruise Control Set Limit (LCC)

Reprogramming the ECM to operate within a different engine horsepower family requires a different personality module and engine part changes. A Caterpillar dealer should be consulted for details.

An alternative method of programming the customer specified parameters that are selected by the customer can be done with the DDT. The DDT also plugs into the Data Link connector in order to communicate with the ECM. The DDT does not accept alphabetic characters. The DDT cannot be used to program some engine parameters.

Both the DDT and the ECAP will read active diagnostic codes and logged diagnostic codes. A partial list of the diagnostic fault codes is listed below.

System Diagnostic Codes

Refer to Troubleshooting, "Truck Engine Test Procedures" for a complete listing of the diagnostic codes and an explanation of each code.

Diagnostic Lamp

The check engine light can be used as a diagnostic lamp in order to communicate the status of the electronic control system. The check engine light can be used to communicate the problems of the electronic control system.

When the ECM detects a diagnostic fault, the check engine light will be turned ON. The check engine light will then blink at five second intervals. The light should also be ON and flashing Diagnostic Code 55 whenever the START switch is turned ON, but the engine is not running. This condition will test whether the light is operating correctly.

If the check engine light remains on after the engine starts, the ECM has detected a system fault code. The check engine light or service tools can be used to identify the diagnostic code.

The dash mounted cruise control switches are used to interrogate the ECM for system status. To interrogate the ECM for the system status, use the following procedure:

1. The cruise control switch must be in the OFFposition.

2. Move the cruise control SET/RESUME switch to the RESUME position.

3. The check engine light will begin to flash in order to indicate a two-digit fault code while the SET/RESUME switch is held in the RESUME position.

4. The sequence of flashes represents the system diagnostic message. The first sequence of flashes adds up to the first digit of the fault code. After a two second pause, a second sequence of flashes will occur. The second sequence of flashes represents the second digit of the fault code. After another pause, any additional fault codes will follow. The additional fault codes will be displayed in the same manner.

The check engine light is also used to monitor the idle shutdown timer. The diagnostic lamp will start to rapidly flash ninety seconds before the idle shutdown feature is reached. If the clutch pedal or the service brake pedal is depressed during the final ninety seconds, the idle shutdown timer will be disabled. The idle shutdown timer will stay disabled until the parking brake is reset.

An operating voltage of 12 Volts is supplied to the check engine light from the vehicle electrical system. The ECM turns on the light by connecting one side of the bulb to ground which completes the electrical circuit.

Electronic Control Module (ECM) and Personality Module

Illustration 6	g00536043
Electronic Control Module and Personality Module (1) Control module plug (2) Data Link receptacle (3) Fuel inlet from transfer pump (4) Fuel outlet to fuel filter base (5) Personality module (6) ECM

The 3406C PEEC III engine uses a microprocessor based electronic control module (ECM) which is mounted on the rear left side of the cylinder block. The electronic control module's temperature is stabilized by the fuel as the fuel circulates through a manifold. The manifold is between the two circuit boards in the ECM. The fuel enters the control module from the fuel transfer pump at fuel inlet (3) and the fuel exits the control module at fuel outlet (4) .

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

The ECM contains memory in order to store the customer specified parameters. The ECM contains memory in order to identify a selected factory engine rating. This memory also contains a personality module identification code in order to prevent the following problems:

• unauthorized tampering

• switching of rating of the personality modules

• other pertinent manufacturing information

The wiring harness provides communication or signal paths to the sensors, the Data Link connector, and the engine/vehicle connectors.

The personality module (5) is installed inside the ECM. The personality module provides the necessary instructions to the ECM. The personality module is required for the ECM to work. The personality module contains all the following performance information and certification information:

• engine timing

• fuel air ratio control

• rated rack control maps for a particular ratings group

Any engine rating from a number of available ratings in that group can be selected through the data link by using a Caterpillar service tool. For example, an engine with a particular personality module can be programmed for any one of six ratings from 213 kW (285 hp) at 1600 rpm to 231 kW (310 hp) at 1900 rpm.

The customer specified parameters include the following parameters:

• "Engine Power Rating"

• "Vehicle Identification Number"

• "PTO Vehicle Speed Limit" (PTO VSL PROTECTION)

• PTO Engine RPM Limit (PTO RPM)

• "Low Gears No. 1 RPM Limit" (LOGR No. 1)

• "Low Gears No. 2 RPM Limit" (LOGR No. 2)

• "Low Gears Turn Off Speeds" (LOGR Off Limits)

• "High Gears Engine RPM Limit" (HIGR RPM)

• "Engine RPM At Vehicle Speed Limit" (ENG RPM At VSL)

• "Top Engine Limit" (TEL)

• "Vehicle Speed Limit" (VSL)

• "High Gear Turn On Speed" (HIGR On)

• "Low Cruise Control Set Limit" (LCC)

• "High Cruise Control Speed Set Limit" (HCC)

• "Retarder Coast/Latch"

• "Idle Shutdown Timer"

The customer specified parameters may be secured by customer passwords. All the parameters can be programmed into the ECM. Any combination of programmed parameters is allowed. Refer to Operation and Maintenance Manual for a brief explanation of each of the customer specified parameters.

The ECM is programmed to run diagnostic tests on all inputs and outputs in order to locate a fault to a specific circuit. Once a fault is detected, the fault can be displayed on the check engine lamp. Refer to the topic "Diagnostic Lamp". The diagnostic code can be read by using a service tool. The ECM will also log most diagnostic codes that are generated during engine operation. These logged codes can be read by using the service tools.

Idle Shutdown Timer

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

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

• The idle shutdown timer feature has been selected.

• The parking brake must be set.

• The parking brake switch must be installed.

• The engine must be at operating temperature.

• The vehicle speed must be at 0 mph.

• No engine load

The check engine light is also used to monitor the idle shutdown timer. The diagnostic lamp will start to rapidly flash ninety seconds before the idle shutdown feature is reached. If the clutch pedal or the service brake pedal is depressed during the final ninety seconds, the idle shutdown timer will be disabled. The idle shutdown timer will stay disabled until the parking brake is reset.

Throttle Position Sensor

Illustration 7	g00536044

A cab mounted throttle position sensor is used in order to eliminate the mechanical linkage that is used between the engine and the throttle foot pedal. The throttle position sensor is a rotary position sensor assembly. The throttle position sensor has 30 degrees of active travel. The throttle position sensor has an additional 5 degrees under travel and 10 degrees over travel for linkage tolerance. The throttle position sensor is environmentally protected. The throttle position sensor is conveniently mounted in the vehicle cab or on the engine side of the fire wall.

The output of the throttle position sensor is a constant frequency pulse width modulated signal (PWM) rather than an analog voltage. The PWM signals overcome the serious errors that can be the result from using analog signals.

The throttle position sensor has been designed to comply with FMVSS124 for the throttle return under the following conditions:

• environmental temperature limits

• missing parts of the throttle linkage

Two return springs for the throttle position sensor are located behind the mounting disc. The engine returns to low idle if the PWM signal is invalid. The signal can be invalid due to the following reasons:

• a broken wire

• a shorted out wire

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

A pedal mounted throttle position sensor (if equipped) can be installed in place of the throttle position sensor on earlier engines as long as the engine has the correct personality module.

The pedal mounted throttle position sensor is mounted on the back of the OEM supplied pedal. Calibration of the pedal mounted throttle position sensor is done automatically by the ECM.

Vehicle Speed Buffer

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

The speedometer should receive the signal directly from the vehicle speed buffer. If the speedometer is not connected directly to the vehicle speed buffer, problems with the following parameters could exist:

• cruise control

• gear parameters

• PTO

• idle shutdown timer

• other parameters

Coolant Temperature

Engine coolant temperature is measured by an electronic sensor that is mounted on the water outlet housing. The sensor's signal is used to modify the engine's fueling and timing. Modifying the engine's fueling and timing improves the engine's cold start characteristics. Modifying the engine's fueling and timing improves the engine's white smoke emissions. The ECM supplies the coolant temperature sensor with 5.0 ± .5 VDC. The sensor's output voltage ranges from .5 to 5.5 VDC. The output depends on the engine coolant temperature.

Coolant Level Sensor

The coolant level sensor is installed by the OEM. The coolant level sensor is the only sensor that is an option for the Caterpillar Engine Protection System. The sensor's function is selectable through a customer parameter.

The sensor operates as a coolant loss sensor that indicates the presence or absence of coolant at the sensor. The sensor is powered from the ECM through the vehicle connector.

Retarder Enable (Compression Brake)

If the engine is equipped with a compression brake, the operation of the compression brake is provided through the retarder enable output. The retarder enable status is determined by the following inputs:

• a brake switch

• a compression brake switch

• a clutch switch

• throttle position

• a cruise switch

• engine rpm

Operation of the compression brake will be inhibited under improper engine operating conditions. The correct operating conditions are the following conditions:

• Engine speed is greater than 950 rpm.

• The clutch is engaged.

• no throttle

• The compression brake switch is ON.

Transducer Module

Illustration 8	g00536046
Transducer Module (1) Camshaft retainer (2) Transducer module (3) Oil pressure sensor (4) Boost pressure sensor

The sealed transducer module is mounted below the rack actuator housing. The transducer module contains the following parts:

• engine oil pressure sensor

• boost pressure sensor

• protective signal conditioning circuitry

Engine oil pressure is supplied to the fuel rack servo and the 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 is routed to the transducer module. Atmospheric pressure is routed to the transducer module from the clean air side of the air filter. This venting of the transducer module is required in order to get an accurate oil and boost pressure reading. Wiring for the rack position and the engine speed signals are passed through the transducer module in order to minimize external connections.

Fuel Rack Controls

Illustration 9	g00536047
Side View of Rack Actuator and Fuel Injection Pump (1) Shutoff solenoid (2) Fuel rack governor servo (3) Shutoff lever (4) Manual shutoff, shutoff override shaft and lever assembly (5) Clearance between camshaft retainer and sensor (6) Camshaft retainer (7) Spring (8) Engine speed sensor (9) Oil pressure sensor (10) Boost pressure sensor (11) Transducer module

Illustration 10	g00536049
Top View of Rack Actuator (2) Fuel rack servo (12) Fuel rack (13) Magnet (14) Rack position sensor (15) Nut (16) Rack solenoid (BTM)

Engine oil pressure is used to move the fuel rack. An electronically actuated rack solenoid (BTM) (16) controls a double acting hydraulic servo. The servo directs engine oil pressure to either side of a piston that is connected to fuel rack (12) which moves the piston and fuel rack as a unit.

The rack solenoid (BTM) (16) is installed in the side of the rack actuator housing at the rear of the fuel injection pump. The rack solenoid is controlled by the ECM. The lever of rack solenoid (BTM) is engaged in a collar on the rack servo valve. The rack solenoid (BTM) is spring loaded toward the Fuel-Off position. The rack solenoid must receive a positive voltage in order to move in the Fuel-On direction.

Rack position sensor (14) is located inside the rack actuator housing. The rack position sensor is attached to fuel rack (12) by magnet (13). The rack position sensor is a linear potentiometer that is used for accurate feedback information for the ECM.

In addition to the rack position data, the ECM receives data from four other sensors that are located in the rack actuator housing and the transducer module. The engine speed sensor (8) is triggered by radial slots on the retainer for the fuel injection pump camshaft. The transducer module contains two sensors (9) and (10) that monitor the engine oil pressure and the boost pressure. The ECM will limit engine speed and power output of the engine if low oil pressure occurs. The control module adjusts the quantity of the fuel or the timing of the fuel that is delivered to the engine when a change in boost pressure is detected.

The ECM operates the shutoff solenoid (1). The shutoff solenoid must be energized in order for the engine to run. If the rack solenoid (BTM) (16) is unable to move the fuel rack (12) to the Fuel-Off position, the shutoff solenoid (1) will apply an additional force on the fuel rack in order to move the rack to the Fuel-Off position. A manual shutoff (4) is provided. The manual shutoff control shaft is spring loaded to a neutral position.

If the shutoff solenoid fails to energize, manual shutoff (4) may be used in order to move the shutoff lever away from the servo valve (2). This will allow rack solenoid (16) to move the fuel rack even though the shutoff solenoid is not energized.

The manual shutoff (4) may be used to shut down the engine while the shutoff solenoid energized and power is maintained to the ECM. This technique is used in some troubleshooting procedures.

The mechanical air/fuel ratio control, the torque control, and various adjustment screws have been eliminated. The ECM performs all of these functions. The control module adjusts engine power and torque rise for the following reasons:

• Operating the engine at high altitudes

• Operating the engine with plugged air cleaners

• Minimizing the amount of smoke

The amount of fuel that is needed by the engine in order to maintain a desired rpm is determined by the ECM. When the engine is running at a desired speed, the engine speed will decrease when an additional load is applied. The signal from Engine Speed Sensor (8) to the ECM changes. The ECM receives this signal and other data. The ECM processes all the data. The ECM then sends a positive voltage to the rack solenoid (BTM) (16). The rack solenoid (BTM) moves the valve in fuel rack servo (2) and the fuel rack (12) 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.

When the engine is running 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 to the rack solenoid (BTM) (16). The rack solenoid (BTM) moves the valve in fuel rack servo (2) and the fuel rack (12) 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.

When starting the engine there is no need to use the accelerator with the PEEC III system. The ECM will automatically provide the engine with the proper amount of fuel in order to start the engine. Since some oil pressure is required for the fuel rack servo to move the fuel rack, the PEEC III engine may require a slightly longer cranking time to start.

Governor Servo

Illustration 11	g00536051
Rack Movement Toward Full Fuel (A) Oil inlet (B) Oil outlet (C) Oil passage (D) Oil passage (E) Pressure oil (F) Drain oil (1) Piston (2) Cylinder (3) Sleeve (4) Valve

When the rack solenoid (BTM) is energized, the rack solenoid 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 goes through oil passage (C) and along valve (4) and out oil outlet (B).

Illustration 12	g00536053
No Rack Movement (Constant Engine Speed) (A) Oil inlet (B) Oil outlet (C) Oil passage (D) Oil passage (E) Pressure oil (F) Drain oil (G) Blocked oil (1) Piston (2) Cylinder (3) Sleeve (4) Valve (5) Fuel rack

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 which stops the piston and fuel rack movement.

Illustration 13	g00536054
Movement Of Rack Toward The Fuel Off Position (A) Oil inlet (B) Oil outlet (C) Oil passage (D) Oil passage (E) Movement of rack toward the fuel off position (F) Pressure oil (G) Drain oil (1) Piston (2) Cylinder (3) Sleeve (4) Valve (5) Fuel rack

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 left side area of the piston is greater than the right side area of the piston. The force of the oil is also greater on the left side of the piston. This moves the piston and fuel rack (5) to the right.

Timing Advance Unit

Illustration 14	g00536055
Front View of Timing Advance Unit (1) Timing solenoid (2) Timing position sensor (3) Bellcrank

Illustration 15	g00536056
Timing Advance Unit Before Any The Timing Advance (A) Pressure oil (B) Blocked oil (C) Drain oil (1) Timing solenoid (4) Sleeve (5) Valve spool (6) Ring (7) Gear (8) Carrier (9) Fuel injection pump camshaft (10) Body assembly (11) Bolt (12) Ring

The timing advance unit connects the drive end of the fuel injection pump camshaft with the timing gears in the front of the engine. The unit uses engine oil pressure to change the fuel injection timing. An electronically actuated timing solenoid (BTM) controls a double acting hydraulic servo. The double acting hydraulic servo directs engine oil that is under pressure to either side of the drive carrier. The side determines if the timing will be advanced or if the timing will be retarded. The total timing advance range is 25 crankshaft degrees.

Timing is controlled by the PEEC III system as a function of the following conditions: engine rpm, load demand (rack position), boost pressure, engine acceleration and throttle position. A timing position sensor is used for accurate feedback control of the timing advance through the ECM and the timing solenoid (BTM). Timing position sensor (2) is located on top of the timing advance actuator housing. Bellcrank (3) is used to transfer linear motion of the timing advance unit to the end of Timing Position Sensor (2). Bellcrank (3) is in contact with a thrust bearing. The thrust bearing is fastened to the timing advance body assembly (10) and the thrust bearing follows the movement of the timing advance body assembly (10) .

The timing solenoid (BTM) (1) is installed toward the inside of the engine into the timing advance actuator housing. The timing solenoid (BTM) is spring loaded toward the retarded position. The timing solenoid (BTM) must receive a positive voltage from the ECM in order to move the servo valve spool that changes the fuel injection timing. The lever of Timing Solenoid (BTM) (1) is connected to servo valve spool (5) through sleeve (4).

The timing advance unit is connected to the fuel injection pump camshaft. Bolts (11) pull rings (6) and (12) together in order to hold gear (7). Carrier (8) has two helical splines. The outer splines are in contact with the helical splines of ring (6) and the inner splines are in contact with the helical splines on fuel injection pump camshaft (9). When the engine is started, gear (7) drives fuel injection pump camshaft (9) through ring (6) and carrier (8).

Advance Timing

Illustration 16	g00536057
Oil Pressure Locations Toward Maximum Timing Advance (A) Pressure oil (B) Drain oil (1) Timing solenoid (4) Sleeve (5) Valve spool (6) Ring (7) Gear (8) Carrier (9) Fuel injection pump camshaft (10) Body assembly (11) Bolt (12) Ring

As the engine begins to run, the ECM sends current to the timing solenoid (BTM) which moves valve spool (4) to the left in the above illustration. At this point, the valve spool (4) closes off the oil drain passage in the body assembly (10). Engine lubrication oil flows through the fuel injection pump housing and through a passage in the fuel injection pump camshaft (9) into the body assembly (10) and the oil is stopped by the valve spool (4). Oil pressure pushes the body assembly (10) and the carrier (8) to the left. As carrier (8) is forced to the left by oil pressure, the carrier slides between the helical splines on ring (6) and the helical splines on the fuel injection pump camshaft (9). The helical splines that are on the carrier and the ring cause the camshaft to turn in relation to gear (7). This outward motion of the body assembly (10) causes the fuel injection timing to be advanced.

Retarded Timing

Illustration 17	g00536058
Retarded Timing (A) Pressure oil (B) Drain oil (1) Timing solenoid (4) Sleeve (5) Valve spool (6) Ring (7) Gear (8) Carrier (9) Fuel injection pump camshaft (10) Body assembly (11) Bolt (12) Ring

When the ECM senses a need for the engine timing to be retarded, the voltage to the timing solenoid (BTM) is reduced. Spring pressure in the timing solenoid (BTM) moves valve spool (4) to the right in the above illustration. This blocks the engine lubrication oil from the oil drain passage on the outer end of body assembly (10). The oil flows from the fuel injection pump camshaft (9), through the body assembly (10) and around the valve spool (4). The oil pressure builds up and the oil pressure moves the body assembly (10) and the carrier (8) to the right. This action causes fuel injection pump camshaft (9) to turn in relation to gear (7) and fuel injection timing is retarded.

Oil Flow for Fuel Injection Pump, Rack Actuator, and Automatic Timing Advance

Illustration 18	g00536059
Fuel Injection Pump and Rack Actuator Oil Flow (A) Pressure Oil (B) Drain Oil (1) Fuel injection pump housing (2) Rack actuator housing (3) Oil passage for the cylinder block (4) Oil drain passage to the cylinder block (5) Transducer module

Lubrication oil under pressure is supplied to the fuel injection pump housing from the left side of the cylinder block through passage (4). At this point, part of the oil flows into a main oil passage in fuel injection pump housing (2) in order to lubricate the three fuel injection pump camshaft bearings. At the camshaft bearing that is next to the rack actuator housing, oil flows between the bearing and the camshaft in order to lubricate the thrust bearing for the camshaft retainer. Oil flows at the camshaft bearing on the drive end of fuel injection pump housing (2) into drilled passages in the camshaft. The oil in the camshaft supplies oil to the timing advance unit. Oil drains from the camshaft bearings into the fuel injection pump housing.

An oil drain hole keeps the level of the oil in the housing even with the center of the camshaft. Oil drains from the housing, through drain port (5) and back to the engine block.

From passage (4), part of the oil is directed back to the passages that are formed between the fuel injection pump housing (2) and the rack actuator center housing. Oil flows through these passages to two different locations. Some of the oil flows through a passage that is between the rack actuator housing and fuel injection pump housing (2). The passage goes to the transducer module (6) which sends an electrical signal to the ECM in order to monitor engine oil pressure.

The remainder of the oil flows through a different passage. The passage goes back through the fuel injection pump housing. This passage is connected to fuel rack servo (1). The fuel rack servo moves the fuel rack through a double acting piston.

The internal parts of the rack actuator housing are lubricated by the following methods:

• oil leakage from the fuel rack servo (1)

• oil that is slung by the rotation of the camshaft retainer

Oil drains back through an opening between the lower part of the rack actuator housing and the fuel injection pump housing. The fuel injection pump housing has an oil drain passage (5) that is connected to the engine block.