Sensores 3500B EUI

777D

AIR INTAKE AND EXHAUST

This sectional view of the engine shows the injector installation and the pushrod arrangement in relation to the upper portion of the engine.

This sectional view is similar to the original 3500 EUI engine. Major differences are the spring loaded injector push rods and the larger diameter camshaft.

Each cylinder has three corresponding camshaft lobes. The center lobe is is used to actuate the unit injector. The 3500B has a larger diameter camshaft to accommodate the higher injection pressures generated in the unit injector pumps.

The cylinder block has a larger camshaft bore to accommodate the larger camshaft. (All 3500 engines are now being manufactured to this standard.)

MUI

EUI

This picture shows the difference between the Mechanical Unit Injection (MUI) and current Electronic Unit Injection (EUI) installation in the cylinder head.

Notice the Helper Spring on the injector pushrod. This arrangement is designed to keep the follower in constant contact with the camshaft. The helper spring is required due to the increased injection pressures of 151 MPa (22000 psi) and the steeper, high lift camshaft lobe profile.

CHAPTER : 3500B

FUEL SUPPL

Y SYSTEM 992G

ELECT

. ENG. CONTROL

PRIMING PUMP SUPPLY

DIFFERENTIAL PRESSURE

SWITCH RETURN FUEL

PRIMARY FILTER TRANSFER PUMP SECONDARY FILTER FUEL TANK ECM FUEL TANK FUEL PRESSURE REGULATOR

This view shows the injector and its fuel supply circuit. A larger volume of fuel passes through the injector than is required for injection. This extra flow is used to cool the injector, which is also surrounded by coolant.

COMPONENT DIAGRAM - 777D

KEY START SWITCH

24 V

P20/J20

J3/P3 MACHINE INTERFACE CONNECTOR

GROUND BOLT P26 T/C CONNECTOR J4/P4 THROUGH J19/P19 J2 J1 ECM UNFILTERED OIL

PRESSURE SENSOR CRANKCASE PRESSURE

SENSOR

J29/P29

RIGHT

TURBOCHARGER INLET PRESSURE

SENSOR J25/P25 ATMOSPHERIC PRESSURE SENSOR TURBOCHARGER OUTLET PRESSURE SENSOR J23/P23

FILTERED OIL PRESSURE

SENSOR

J22/P22

LEFT

TURBOCHARGER INLET PRESSURE

SENSOR

J28/P28

J35/P35

THROTTLE POSITION SENSOR

THROTTLE BACK-UP SWITCH

USER DEFINED SHUTDOWN

GROUND LEVEL SHUTDOWN SWITCH

BATTERY

ENGINE FAN CONTROL SOLENOID

A/C ON SWITCH

FAN SPEED SENSOR

+ BATTERY RELAY

CYLINDER

ENGINE

ETHER START VALVE

STARTING _{AID SWITCH}

J21/P21 J32/P32 J105/P105 J106/P106 J47/P47 P30/J30 J27/P27 J48/P48 P84/J84 P41/J41 308-YL 113-OR

BASIC ENGINE BLOCK DIAGRAM

APPLICATION BLOCK DIAGRAM

ELECTRONIC SERVICE TOOL CONNECTOR

MONITORING SYSTEM DISCONNECT SWITCH 15 AMP BREAKER J4/P4 THROUGH J19/P19 RELAY J21/P21 J47/P47 P31/J31 0 5 10 15 20 25 30 X100 24 V MPHkm/h 44 AUT P R

P22 J22 ENGINE COOLANT TEMPERATURE SENSOR FILTERED OIL PRESSURE SENSOR +V ANALOG ANALOG RETURN SIGNAL +V ANALOG ANALOG RETURN SIGNAL P23 J23 TURBO OUTLET PRESSURE SENSOR +V ANALOG ANALOG RETURN SIGNAL P25 J25

RIGHT TURBO INLET PRESSURE SENSOR +V ANALOG ANALOG RETURN SIGNAL P27 J27 ATMOSPHERIC PRESSURE SENSOR +V ANALOG ANALOG RETURN SIGNAL P28 J28

LEFT TURBO INLET PRESSURE SENSOR +V ANALOG ANALOG RETURN SIGNAL 36 30 P1 J1 P43 J43 +V ANALOG ANALOG RETURN SIGNAL CRANKCASE PRESSURE SENSOR P48 J48 +V ANALOG ANALOG RETURN SIGNAL UNFILTERED OIL PRESSURE SENSOR A B C A B C A B C A B C A B C A B C A B C A B C J21 P21 5 ± 0.5 VOLTS +V ANALOG SUPPLY ANALOG RETURN ECM

The Analog Sensor Power Supply provides power to all the analog sensors (pressure and temperature).

The ECM supplies 5.0 ± 0.5 Volts DC (Analog Supply) through the J1/P1 connector to each sensor.

A power supply failure will cause all analog sensors to appear to fail.

The power supply is protected against short circuits, which means that a short in a sensor or a wiring harness will not cause damage to the ECM.

DIGITAL SENSOR POWER SUPPLY

8

±

0.5 VOLTS

The ECM supplies power at 8 ± 0.5 Volts through the J1/P1 connector to the following circuits:

- Throttle Position Sensor - Fan Speed Sensor (if installed) - Exhaust Temperature Sensors

The power supply is protected against short circuits, which means that a short in a sensor will not cause damage to the ECM

SYSTEM POWER SUPPLIES

The 3500B EUI system has one external and five internal power supplies with various voltages as shown.

EXTERNAL POWER SUPPLIES

ECM power supply 24 Volts

INTERNAL POWER SUPPLIES

Speed/Timing Sensor power supply 12.5 Volts Injector power supply 105 Volts Analog Sensor power supply 5 Volts Digital Sensor power supply 8 Volts Wastegate Control Solenoid power supply 0 - 24 Volts

ECM Power Supply

The power supply to the ECM and the system is drawn from the 24-Volt machine battery. The principle components in this circuit are:

- Battery

- Key Start Switch - Main Power Relay - 15 Amp Breaker - Ground Bolt

- ECM Connector (P1/JI)

- Machine Interface Connector (J3/P3)

If the supply voltage exceeds 32.5 Volts or is less than 9.0 Volts, a diagnostic code is logged. (See the Troubleshooting Guide for complete details on voltage event logging.)

NOTE: The Ground Bolt and the Machine Interface Connector are the only power supply components mounted on the engine.

COMPONENT DIAGRAM

Injector Power Supplies

The injectors are supplied with power from the ECM at 105 Volts. For this reason, precautions must be observed when performing maintenance around the valve covers.

On the 3512B and 3516B, two of the internal power supplies are used for the injectors. If a failure occurs, only one bank of injectors could have failed. On the 3508B, only one of the internal power supplies is used. As previously mentioned, the same ECM is used on all three configurations.

If an open or a short occurs in the injector circuit, the ECM will disable that injector. The ECM will periodically try to actuate that injector to determine if the fault is still present and will disconnect or reconnect the injector as appropriate.

Speed/Timing Sensor

One Speed/Timing Sensor is installed and it serves four basic functions in the system:

- Engine speed detection - Engine timing detection

- Cylinder and TDC identification - Reverse rotation protection

The ECM supplies 12.5 ± 1 Volts to the Speed/Timing Sensor.

Connector pins A and B transmit the common power supply to the sensor. The C connector pin transmits the signals from the sensor to the ECM.

This power supply is not battery voltage, but is generated and regulated within 1.0 Volt by the ECM. This power supply and the Speed/Timing Sensor are vital parts of the EUI system. A failure of the sensor will result in an engine shutdown.

The Speed/Timing Sensor is mounted on the rear housing and is

self-adjusting during installation.

This type of sensor does not have a typical fixed air gap. However, the sensor is not in direct contact with the timing wheel, but does run with zero clearance. A Speed/Timing Sensor failure will cause an engine shutdown.

The sensor may be functionally checked by cranking the engine and observing the service tool status screen for engine rpm.

A sensor failure will be indicated by the active fault screen on the service tool. An intermittent failure will be shown in the logged fault screen.

The sensor has a dedicated power supply. A power supply failure at the ECM will cause the sensor to fail.

The sensor head is extended prior to installation. The action of screwing in the sensor pushes the head back into the body after the head contacts the timing wheel.

During installation, it is essential to check that the sensor head is not aligned with a wide slot in the timing wheel. If this condition occurs, the head will be severed when the engine is started, and some disassembly may be necessary to remove the debris.

Timing calibration is normally performed after the following procedures:

1. ECM replacement

2. Speed/timing sensor replacement 3. Engine timing adjustment

COMPONENT DIAGRAM

The engine Coolant Temperature Sensor is located at the front of the engine on the thermostat housing. This sensor is used with the ECM to control various functions. The following systems or circuits use the Temperature Sensor output to the ECM:

The Vital Information Management System (VIMS) or Caterpillar Monitoring System Coolant Temperature Gauge over the CAT Data Link.

The High Coolant Temperature Warning Alert Indicator and Gauge on the VIMS or Caterpillar Monitoring System panel. (The information is transmitted over the CAT Data Link.)

The Engine Demand Fan Control, if installed, uses the sensor signal reference to provide the appropriate fan speed.

The Cat Electronic Technician (ET) status screen for coolant temperature indication.

The Cold Mode engine control (i.e. elevated low idle and timing reference for cold mode operation). The Ether Aid control as a reference for Ether Aid operation.

The sensor supplies the temperature signal for the following functions:

- Caterpillar Monitoring System or VIMS instrument display, warning lamps and alarm - Demand Control Fan (if so equipped)

- ET or ECAP coolant temperature display

- High coolant temperature event logged above 107°C (225°F)

- Engine Warning Derate when 107°C (225°F) is exceeded or low oil pressure occurs (if so equipped)

- Reference temperature for Cold Mode operation

The Aftercooler Temperature Sensor is mounted at the rear of the block (Off-highway Truck) and measures coolant temperature in the aftercooler circuit.

The ECM uses the sensor signal as a reference for the fan control. When high aftercooler temperatures are reached, the cooling fan speed is increased. Very high aftercooler temperatures will cause a VIMS warning event to be logged.

NOTE: This sensor measures the ability of the aftercooler to cool the air sufficiently for combustion. As a general rule, for every 1 degree that the combustion air is reduced in temperature, the exhaust will be reduced by approximately 3 degrees. High inlet manifold temperatures can significantly shorten the life of exhaust system components (i.e. exhaust manifolds, valves, turbochargers and pistons).

Three pressure sensors are used for the measurement of oil pressure:

- Two Oil Pressure Sensors (filtered and unfiltered) - Atmospheric Pressure Sensor

The filtered and unfiltered pressure sensors are used together to measure oil filter restriction.

The filtered oil pressure sensor is used to measure lubrication oil pressure for the operator on the dash panel and for the technician on ET. The atmospheric pressure sensor is used with this oil pressure sensor to calculate the gauge pressure reading.

OIL PRESSURE MAP

OIL PRESSURE IN kPa

600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 60 80 100 120 140 160 180 200 220 240 260 280 300 ENGINE RPM 1900 320 340 8.7 11.6 14.5 17.4 20.3 23.2 26.1 29 31.9 34.8 37.7 40.6 43.5 46.4 49.3

OIL PRESSURE IN PSI

kPa x 0.145 = PSI

2000

Engine oil pressure varies with engine speed. As long as oil pressure increases above the upper line after the engine has been started and is running at low idle, the ECM reads adequate oil pressure. No faults are indicated and no logged event is generated. A delay built into the system prevents false events from being logged after start-up or after a filter change.

If the engine oil pressure decreases below the lower line, the following occurs:

- An event is generated and logged in the permanent ECM memory.

- A Category 3 Warning (alert indicator, action lamp and alarm) is generated on the VIMS and Caterpillar Monitoring System.

- The engine is derated (if so equipped) to alert the operator.

The width of the pressure band between the two lines is sufficient to prevent multiple alarms and events or a flickering warning lamp. (This pressure separation is referred to as hysteresis).

The Atmospheric Pressure Sensor is installed on the ECM mounting adapter and is vented to the atmosphere. This sensor has various functions which are fully described later in the presentation. Briefly, it performs the following functions:

Ambient pressure measurement for automatic altitude compensation and automatic air filter

compensation.

Absolute pressure measurement for the fuel ratio control, ET, filter restriction, and Caterpillar

Monitoring System panel (gauge) pressure calculations.

All pressure measurements require the atmospheric pressure sensor to calculate gauge pressure. All pressure sensors in the system measure absolute pressure. The sensors are used individually in the case of atmospheric pressure (absolute pressure measurement). They are used in pairs to calculate gauge pressures (oil and boost) and filter restriction.

All the pressure sensor outputs are matched to the Atmospheric Pressure Sensor output during

calibration. Calibration can be accomplished automatically using the ET service tool or by turning on the key start switch without starting the engine for five seconds. The Atmospheric Pressure Sensor performs four main functions:

1. Automatic Altitude Compensation (Maximum derate 24%) 2. Automatic Filter Compensation (Maximum derate 20%) 3. Part of the pressure calculation for gauge pressure readings 4. Reference sensor for pressure sensor calibration

ENGINE POWER DERATING MAP

ACCORDING TO ATMOSPHERIC PRESSURE

ATMOSPHERIC PRESSURE IN kPa

PERCENT OF FULL LOAD POWER

ALTITUDE IN FEET

Atmospheric pressure measurement by the sensor provides an altitude reference for the purpose of

Automatic Altitude Compensation.

The graph shown here describes how derating on a typical 3500B starts at 7500 ft. and continues linearly to a maximum of 17000 ft. Other engines may start between 4000 and 12000 ft. depending on the application.

The advantage of the EUI system is that the engine always operates at the correct derating setting at all altitudes. The system continually adjusts to the optimum setting regardless of altitude, so the engine will not exhibit a lack of power or have smoke problems during climbs or descents to different altitudes.

NOTE: The EUI system has an advantage over a mechanical fuel system which is derated in "altitude blocks" (i.e. 7500 ft., 10000 ft., 12500 ft.). EUI derating is continuous and automatic. Therefore, a machine operating in the lower half of the block is not penalized with low power. Conversely, a machine operating in the upper half of the block will not overfuel with the EUI system.

The Turbocharger Inlet Pressure Sensor is mounted between the air filter and the turbocharger.

This sensor is used in conjunction with the atmospheric pressure sensor to measure air filter restriction for engine protection purposes. The difference between the two pressure measurements is used as the filter differential pressure. The engine ECM uses this calculation to determine whether derating is necessary to protect the engine against the effects of excessive filter restriction.

This function is referred to as Automatic Air Filter Compensation.

Depending on the application and air intake system configuration, either one or two Turbocharger Inlet Pressure Sensors may be used.

If the machine is equipped with an ether start system, the ECM will automatically inject ether from the ether cylinders) during cranking. The operator can also inject ether manually with the ether switch in the cab. Ether will only be injected if the engine coolant temperature is below 10°C (50°F) and engine speed is below 1200 rpm.

COMPONENT DIAGRAM

Automatic Filter Compensation means that the engine is protected against the effects of plugged filters.

Derating is automatic as follows:

- Air filter restriction (∆P) exceeds 6.25 kPa (30 in. of water) - Engine power derating starts at the rate of 2% per 1 kPa of ∆P - Maximum derate 20%

- Event is logged when air filter restriction (∆P) exceeds 6.25 kPa (30 in. of water)

These ∆P specifications are typical examples. The actual values may vary depending on the application. Derating is retained at the maximum ∆P until the key start switch is cycled off and on.

NOTE: If only one filter is plugged, the ET service tool and Caterpillar Monitoring System will display the highest ∆P of the two. Derating is also based on the highest ∆P of the two.

The Turbocharger Outlet Pressure Sensor measures absolute pressure downstream of the aftercooler. Boost (gauge) pressure can be read with the service tools. This measurement is a calculation using the Atmospheric Pressure and the Turbocharger Outlet Pressure Sensors.

A failure of this sensor will cause the ECM to default to a zero boost condition. This failure can result in a 60% loss in engine power.

The function of the sensor is to enable the Air/Fuel Ratio Control which reduces smoke, emissions and maintains engine response during acceleration. The system utilizes manifold pressure and engine speed to control the air/fuel ratio. Engine fuel delivery is limited according to a map of gauge turbo outlet pressure and engine speed.

The ECM uses gauge pressure measured from the Crankcase Pressure Sensor and the Atmospheric Pressure Sensor to determine whether crankcase pressure is excessive (i.e. a piston allowing excessive blowby which could soon cause considerable damage).

The ECM will warn the operator of possible damaging conditions and record adverse conditions in the memory.

A possible cause of excessive crankcase pressure could be piston damage or a piston ring failure. An early warning means that the engine can be shut down without catastrophic secondary damage.

Crankcase pressure is compared with atmospheric pressure. The result is crankcase (gauge) pressure (i.e. pressure above ambient).

The trip points are:

WARNING 2 kPa (10 in. of water) EVENT 3.5 kPa (17in. of water)

COMPONENT DIAGRAM

Two Exhaust Temperature Sensors are installed on the 793C. The sensors are mounted between the exhaust manifold and the turbocharger.

The ECM uses the sensors to warn the operator of possibly damaging conditions and logs an event in the memory.

An engine derate occurs on Off-highway Trucks if excessive exhaust temperatures are reached.

The Throttle Position Sensor provides engine speed control for the operator.

At engine start-up, the engine rpm is set to low idle for two seconds to allow an increase of oil pressure before the engine is accelerated.

The Throttle Position Sensor receives 8 Volts from the Digital Sensor Power Supply at the ECM.

The Throttle Position Sensor is shown on the machine wiring side of the diagram.

NOTE: This system eliminates all mechanical linkage between the operator's engine speed controls and the governor (ECM).

Demand Fan Controls

Two types of thermostatic fans are used in 3500B machine applications. Some Off-highway Trucks and Track-type Tractors are equipped with a variable speed fan drive clutch. Some Wheel Loaders are equipped with a hydraulic fan drive.

Both systems use the ECM and the temperature sensor as the engine coolant temperature reference, and both are controlled by the ECM. If an electrical failure of the system occurs, the fan will go to maximum (100%) speed.

The advantages of the systems are:

- Reduced fuel consumption in most conditions

- Reduced engine overcooling at low ambient temperatures - Faster engine warm-up

- More engine power available at the flywheel - Reduced noise

Engine Mounted Switches

Three EUI circuit switches are mounted on the engine:

The Low Oil Level Switch signals the ECM if the engine oil level decreases below a predetermined level. The ECM then warns the operator of possible damaging conditions and logs an event.

The Filter Differential Pressure Switch signals the ECM if the pressure across engine fuel filter is excessive and the filter needs to be changed.

The Coolant Flow Switch provides the operator with a warning if a failure in the coolant circuit causing no flow occurs. The switch contacts are normally open with no flow.

The Coolant Flow Switch, like the Oil Level Switch, is a passive sensor (i.e. no power supply) which means that the ECM cannot determine if the switch or associated circuit has failed. A system problem could be determined if coolant flow is indicated with the engine stopped or if no coolant flow is indicated with the engine running.

COMPONENT DIAGRAM

The Throttle Back-up Switch provides a "limp home" mode in the event that the Throttle Position Sensor becomes inoperative.

If the ECM detects either an invalid or no signal, the Throttle Back-up Switch is automatically activated. When activated, the operator may operate the switch to raise the engine speed to 1200 rpm for as long as the switch is operated. If the Throttle Position Sensor signal is received again, the switch is deactivated.

Engine Shutdown Systems

The Ground Level Shutdown Switch is connected to the ECM through the machine and engine wiring harnesses.

The switch signals the ECM to cut electrical power to the injectors, but maintains power to the ECM.

This feature also enables the engine to be cranked without starting for maintenance purposes.

No other circuits may be connected to this system. The user defined shutdown feature may be used in conjunction with other circuits.

The User Defined Shutdown feature (if installed) may be used to connect another device to the system to shut down the engine (such as a customer installed fire suppression system). When the shutdown input is grounded for one second, the engine will stop running. The input must be pulled down below 0.5 Volts before the ECM will recognize the shutdown signal.

Operation of the User Defined Shutdown is logged as an event and can also be shown on the ET status screen.

For example, when installed on an Off-highway Truck, this feature is programmed to function only during the following conditions:

Parking brake is ENGAGED Transmission is in NEUTRAL Machine ground speed is at zero

Ether Injection System

The ECM controls the use of ether for cold starting. The ECM uses inputs from the speed/timing and coolant temperature sensors to determine the need for ether.

The ECM cycles the ether for three seconds on and three seconds off. Actual flow is determined by engine speed and temperature. Ether injection is disabled when the coolant temperature exceeds 10°C (50°F) or engine speed exceeds 1200 rpm.

A manual mode allows ether injection when the above parameters permit. In the manual mode, a continuous flow of ether is injected. The ether injection status can be read on the ET status screen.

Prelubrication System

The ECM controls the prelubrication system. This system uses the coolant temperature, engine speed and oil pressure as its references to determine the need for prelubrication.

The system is activated when the key start switch is turned to the start position. The system prevents starter motor engagement until the oil pressure increases.

LOGGED EVENTS

Logged events listed on the appropriate ET screen are conditions which are abnormal to the operation of the engine. For example:

- High coolant temperature - Low oil pressure

- Filter restriction

- Excessive engine speed

These events are not normally electronic problems, but might be conditions caused by a plugged radiator, low oil level, maintenance or operator deficiencies.

A list of possible events for the 3500B engine is included on the next page.

Some of the parameters listed in this presentation are used in the ET events list. They are as follows:

- High coolant temperature - High exhaust temperature - High aftercooler temperature - Crankcase pressure

- Loss of coolant flow

- Low (lubrication) oil pressure (according to the oil pressure map) - User defined shutdown

- Air filter restriction - Fuel filter restriction - Oil filter restriction - Engine oil level

- Engine overspeed histogram - High boost

CHAPTER : 3500B

DA

T

A LINK DIAGRAM (992G)

ELECT

. ENG. CONTROL

CHAPTER : 3500B

VIMS DIAGRAM (992G)

ELECT

. ENG. CONTROL

CAT DATA LINK SERVICE KEYSWITCH ACTION LAMP ACTION ALARM ELECTRONIC TECHNICIAN (ET)

VIMS MAIN MODULE

DISPLAY DATA LINK VIMS

RS-232 PORT

CAT DATA LINK

VITAL INFORMATION

MANAGEMENT SYSTEM

(VIMS)

REFERENCE EDGE TO TDC DISTANCE

REFERENCE

EDGE ASSUMED

CYL. NO. 1 TDC _{CYL. NO. 1 TDC}ACTUAL

TIMING REFERENCE

OFFSET

MAXIMUM TIMING REFERENCE OFFSET ± 7 DEGREES TIMING CALIBRATION SENSOR SIGNAL TIMING WHEEL ± 7 ° -7° +7°

As the Speed/Timing Sensor uses the timing wheel for a timing reference, timing calibration improves fuel injection accuracy by correcting for any slight tolerances between the crankshaft, timing gears and timing wheel.

During calibration, the offset is saved in the ECM EEPROM (Electrically Erasable Programmable Read Only Memory). The calibration offset range is limited to ± 7 crankshaft degrees. If the timing is out of range, calibration is aborted. The previous value will be retained and a diagnostic message will be logged.

The timing must be calibrated after performing the following procedures:

1. ECM replacement

2. Speed/timing sensor replacement 3. Timing wheel replacement

E -TRIM CODE READING

PART No.

TRADE MARK

SERIAL No.

TRIM CODE

The code identifies the discharge and timing characteristics of the injector and is programmed into the ECM.

If the injector is replaced, the new code must be entered via ET’s calibration menu.

ALL ENGINES BUILD STARTING MAY 15, 1996 HAVE THE E-TRIM FEATURE ON THEIR PERSONALITY MODULE AND INJECTORS CODED WITH AN E-TRIM CODE

THE SOFTWARE COMPENSATES FOR INJECTOR VARIATION IN TIMING AND DISCHARGE. THE E-TRIM IS A 4 DIDGIT CODE ETCHED ON THE INJECTOR TAPPET

IF IT IS NOT POSSIBLE TO REPROGRAM AN INJECTOR CODE IMMEDIATELY THE ENGINE WILL NOT BE SEVERELY HARMED , ALTHOUGH IT SHOULD BE REPROGRAMMED AS SOON AS POSSIBLE TO OPTIMIZE ENGINE PERFORMANCE AND PREVENT ANY LONG TERM DETRIMENTAL EFFECTS

CAT Electronic technician - Calibrations

CAT Electronic technician - Calibrations

Select Calibration

ENGINE 3508B

Pressure Sensor Calibration

Timing Calibration

Injector Code calibration

Injector 1 1100 Injector 2 1100 Injector 3 1100 Injector 4 1100 Injector 5 1100 Injector 6 1100 Injector 7 1100 Injector 8 1100

Injector

Code

COLD MODE TIMING

30° C 50° C 60° C

COOLANT TEMPERATURE IN DEGREES FAHRENHEIT

LOW ENGINE SPEED FIXED TIMING

HIGH ENGINE SPEED

TO WARM MODE TIMING ADVANCE BTDC Cold Mode

The desired timing is retarded during Cold Mode operation based on coolant temperature and engine speed.

1. For coolant temperatures at or below 86°F:

Timing will be retarded to protect the engine against high cylinder pressures. Idle is elevated to 1300 rpm (with parking brake ON and transmission in NEUTRAL).

2. For coolant temperatures above 86°F and below 140°F, the timing will advance. For engine speeds below 1200 rpm, timing will vary according to the low engine speed line.

VALID NUMBERS -25 to +25

-25

+25

LESS SMOKE

SLOWER RESPONSE

MORE SMOKE

FASTER RESPONSE

0

Acceptable

response

Clean exhaust

© 1994 Deneba Systems, Inc. © 1994 Deneba Systems, Inc.

The Fuel Ratio Control has been optimized to provide excellent performance and black smoke control without any need for adjustment. There should be no need to use the “Fuel Ratio Control Offset” except for special circumstances.

Changing the Fuel Ratio Control Offset parameter allows the customer tailoring of the fuel to air ratio in order to compensate for winter blend fuel, individual costumer preference etc.

COLD START LOGIC

The ECM cuts out each cylinder for a

brief amount of time to see if that

tor is contributing to power. If not

injec-tion will be stopped to that cylinder.

TheECM will retest any cutout cylinder

(injector) every so often to see if it

start-ed to fire or not.

HELPS REDUCE WHITE SMOKE DURING

In cold mode the ECM stops injection

to non-firing injectors until the engine

has reached a certain temperature (coolant

temperature).