System Operation, Testing And Adjusting For The Caterpillar Ignition System (CIS){1550} Caterpillar

Engines:

G3606 (S/N: 3XF)

G3608 (S/N: 4WF)

G3612 (S/N: 1YG)

G3616 (S/N: 4CG)

Introduction

The Caterpillar Ignition System (CIS) has been designed in conjunction with the Caterpillar Timing Control Module (TCM) for use on natural gas fueled engines. This system is designed to replace both the Altronic III and the Altronic Interface Box. New features include advanced spark control, primary diagnostics, spark diagnostics, self diagnostics, pickup diagnostics, and serial communications. The system consists of two main parts: an engine mounted Ignition Module and an optional user interface Display Module.

This Special Instruction offers the procedures to be used in the operation of the ignition system. Ensure that the procedures are read and understood before beginning work on the engine.

Reference: Consult the following manuals for instructions regarding installation:

• Special Instruction, REHS0188, "Installation Procedure For The Caterpillar Ignition System (CIS) On The G3606 Engine"

• Special Instruction, REHS0186, "Installation Procedure For The Caterpillar Ignition System (CIS) On The G3608 Engine"

• Special Instruction, REHS0187, "Installation Procedure For The Caterpillar Ignition System (CIS) On The G3612 Engine"

• Special Instruction, REHS0189, "Installation Procedure For The Caterpillar Ignition System (CIS) On The G3616 Engine"

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Personal injury can result from improper engine operation. Deviation from these installation instructions can result in improper engine operation which could cause personal injury. Follow the installation instructions before engine operation.

Ignition Module Timing Switch, LED Indicators, And Computer Serial Port

1. A rotary switch with 16 positions is installed inside the CIS Ignition. This switch is used in the "Mag-Cal" mode of the Caterpillar TCM in order to adjust the retarding effect from the Hall Effect's signal. This is done in order to stimulate the timing that was formerly provided by the Altronic III at low engine rpm. Adjustment of this switch simulates rotating the Altronic III mechanical position. The timing range is from 0 degrees to 15 degrees with a 1 degree resolution.

2. Five LED indicators are provided inside the Ignition Module for troubleshooting purposes.

   1. The red "Power LED" is continuously illuminated when the unit is powered and the microprocessor is running.

   2. The red "Power LED" flashes when the "Power LED" is not operating correctly and the unit has power.

   3. The red "Power LED" is off when the unit has no power.

   4. The red "TX LED" flashes when the unit is transmitting on the RS-485 serial link.

   5. The red "RX LED" flashes when the unit has received a transmission on the RS-485 serial link.

   6. The red "ALARM LED" illuminates in order to indicate a warning or a fault is present.

   7. The green "H.E. PICKUP LED" illuminates when a magnet turns on the Hall Effect sensor.

3. One RS-485 serial communications port is provided within the Ignition Module. This port is normally used for communication to the optional Display Module.

The Display Module

1. The Display Module serves as the customer interface module for the CIS system. A RS-485 serial communications port is used in order to connect the Display Module to the Ignition Module.

2. An alphanumeric LCD display is used in order to provide an output to the user. A keypad with a sealed membrane is used in order to input the user's data. The LCD display and the keypad function together in order to provide an interactive customer interface module. The interface prompts the user as different functions are selected.

3. All actions and adjustments are immediate. The actions and adjustments are performed on an incremental basis by using the up arrow and the down arrow. All of the entries from the keypad are performed in the Electronically Erasable Programmable Read Only Memory (EEPROM). This EEPROM retains previous settings even after an engine shutdown or an ignition power shutdown.

4. Large letters are used on the display screen in order to designate an active selection. Small letters are used in order to indicate other possible options.

Understanding The Home Screen

1. A series of home screens are used in order to describe the current status of the ignition system. The LCD always reverts to one of the home screens after an operation is completed. The LCD will also revert to one of the home screens if an operation takes too much time. The home screen is designed in order to display the most critical operating parameters on one screen.

2. All of the home screens show the status of the ignition in the upper left hand corner. The engine speed is displayed in the upper right corner. The status of the TCM is displayed on the lower portion of the screen.

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Illustration 1	g00329085

3. The "READY" message is displayed in the upper left hand corner when the ignition is ready to begin cranking the engine. The TCM would normally be in the Manual Mode.

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Illustration 2	g00329096

4. Once the engine begins turning, the "SYNCING" message is displayed while the engine verifies signals from the engine pickups. The proper signals can be identified in as few as two engine revolutions.

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Illustration 3	g00329097

5. The "FIRING" message is displayed when the ignition begins firing. Additional data is provided on this screen in order to describe the selected mode of operation for the ignition. The level of energy (E1, E2, E3) is in the middle of the upper screen in small characters. The type of striking is positioned next to the level of energy. The TCM is displayed in the AUTO Mode.

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Illustration 4	g00329098

6. The "STOPPED" message is displayed when a loss of rotation is detected. The "STOPPED" message is displayed when both a "SHUTDOWN" and a "FAULT" have not occurred. This signifies that the engine has stopped without any detected cause from the ignition system.

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Illustration 5	g00329099

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Illustration 6	g00329100

7. The "WARNING" message will supersede all of the home screens if a diagnostic warning condition is present. When a diagnostic warning exists, a "VIEW DIAGNOSTICS" message will flash on the bottom of the display. The Ignition Module will continue operating under a warning condition while the alarm alerts the operator of a potential problem. The Ignition Module alerts the operator by turning on the alarm in the Ignition Module and by displaying the "WARNING" message. The various types of diagnostic warnings are described in ""Diagnostics For The Ignition System" ".

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Illustration 7	g00329101

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Illustration 8	g00329102

8. The "FAULT" message will supersede all of the home screens if a diagnostic fault condition is present. When a diagnostic fault exists, a "VIEW DIAGNOSTICS" message will flash on the bottom of the display. The ignition system will stop operating under a fault condition while the alarm alerts the operator to the problem. The Ignition Module alerts the operator by turning on the alarm in the Ignition Module and by displaying the "FAULT" message. The various types of diagnostic warnings are described in ""Diagnostics For The Ignition System" ".

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Illustration 9	g00329103

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Illustration 10	g00329104

9. The "SHUTDOWN" screen will supersede all of the home screens if the G-Lead of the primary connector is grounded. The "SHUTDOWN" screen will remain until the ground has been removed and the engine has stopped rotating. This screen indicates that the ignition is not firing because the G-Lead has been grounded in order to shut down the engine. Both the diagnostic fault and the diagnostic warning will cause a "VIEW DIAGNOSTICS" message to flash on the bottom of the display while the engine is shutdown.

Adjusting The Global Retard And The Manual Retard

Global retard is an adjustment that affects the timing of all cylinders equally. This adjustment affects the timing only when the TCM is in manual mode. The default setting for manual retard is 10 degrees. Adjustments that are made will be utilized until another adjustment is made. The manual range for most engines is from 0 degrees to 20 degrees of retardation from the "Mag-Cal" timing.

Note: This range is limited to 10 degrees on some of the engines.

Use the following Steps to adjust the global retard:

Start at the following screen:

Illustration 11	g00329777

Press the "TIMING" key:

Illustration 12	g00329778

Continue from the following screen:

Illustration 13	g00330984

Press the up arrow:

Illustration 14	g00329780

Illustration 15	g00329781

From the screen that is shown above, press the up arrow in order to increase the retardation:

Illustration 16	g00329780

Press the down arrow in order to decrease the retardation:

Illustration 17	g00329782

Press the "NEXT" key in order to view the "Mag-Cal" switch:

Illustration 18	g00329784

Press the "ESC" key in order to exit:

Illustration 19	g00329783

The amount of change in timing is dependent on the number of teeth that are being sensed. With 255 teeth, the increment in timing is 0.176 degrees.

Viewing The Position Of The "Mag-Cal Switch"

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Illustration 20	g00330635

1. Pressing the "NEXT" key allows you to move from the manual retard screen to the "Mag-Cal Switch" screen.

Adjusting The Individual Offsets

The individual cylinder's offsets are configured as "READ ONLY" when the Display Module is used. The individual cylinder's offsets can be viewed, but the offsets can not be adjusted.

Timing Menu

Use the following Steps in order to enter the menu for timing of the individual cylinders.

Start from the following screen:

Illustration 21	g00330983

Press the "TIMING" key:

Illustration 22	g00329778

Continue from the following screen:

Illustration 23	g00330984

Press the down arrow:

Illustration 24	g00329782

Illustration 25	g00330985

From the screen that is shown above, press the up arrow:

Illustration 26	g00329780

Individual Timing

The screen for adjusting the individual timing identifies the primary output that should be changed. The screen also displays the degrees of offset that are presently active. The default setting for all of the outputs is 0 degrees from the global retard. This setting can not be adjusted from the Display Module.

Continue from the following screen:

Illustration 27	g00330986

Press the "NEXT" key in order to select the next cylinder:

Illustration 28	g00329784

Press the "ESC" key in order to exit:

Illustration 29	g00329783

Output Identification Characters

The output's characters are provided on Table 1. This identification is used in order to determine the engine cylinder's number.

Table 1

Harness	A	B	C	D	E	F	K	L	M	N	P	R	S	T	U	V
G3606	1	5	3	6	2	4
G3608	1	6	2	5	8	3	7	4
G3612	1	12	9	4	5	8	11	2	3	10	7	6
G3616	1	2	5	6	3	4	9	10	15	16	11	12	13	14	7	8

Setting Up The Controls

The features of the additional controls and displays can be accessed in the setup menu. Changes that are made in the setup menu are stored in EEPROM. The changes remain fixed until the user alters the setup.

Use the following Steps in order to enter the menu for setting up the controls:

Start at the following screen:

Illustration 30	g00331103

Press the "SETUP" key:

Illustration 31	g00329853

Multi-Strike Setup

Enabling and disabling of the Multi-Strike feature can be done in the first menu.

Note: The Multi-Strike feature is automatically turned off above 1050 rpm. Multi-Strike may accelerate the spark plug electrode's erosion. The Multi-Strike feature fires the spark plug 2 times per event. The default setting is Single-Strike.

Start at the following screen:

Illustration 32	g00331105

Press the up arrow in order to turn on Multi-Strike:

Illustration 33	g00329780

Press the down arrow in order to turn off Multi-Strike:

Illustration 34	g00329782

Press the "NEXT" key for the next option:

Illustration 35	g00329784

Press the "ESC" key in order to exit:

Illustration 36	g00329783

Setting Up The Level Of Energy

The operator can select the level of energy in the second menu. The level of energy for E1 is 75 mJ. The level of energy for E2 is 100 mJ. The level of energy for E3 is 125 mJ.

Note: The energy is automatically limited to E2 when Multi-Strike is active. Higher levels of energy may accelerate the spark plug electrode's erosion. The factory setting is E2.

Start at the following screen:

Illustration 37	g00331106

Press the up arrow in order to increase the level of energy:

Illustration 38	g00329780

Press the down arrow in order to decrease the energy level:

Illustration 39	g00329782

Press the "NEXT" key for the next option:

Illustration 40	g00329784

Press the "ESC" key in order to exit:

Illustration 41	g00329783

Overspeed Setpoint

The next menu is used in order to view the engine's overspeed setpoint. The Display Module cannot adjust the setpoint.

Illustration 42	g00331284

Note: The factory setting is 2200 rpm, which disables this feature.

Special Features

The next screen is used in order to view the special features that are available for start-up. Special features cannot be selected through the Display Module.

Start at the following screen:

Illustration 43	g00331285

Press the "ENTER" key in order to view the special features:

Illustration 44	g00329851

Press the "NEXT" key for the next option:

Illustration 45	g00329784

Press the "ESC" key in order to exit:

Illustration 46	g00329783

"Muti-Strike"

Illustration 47	g00331286

When the Multi-Strike special feature is turned on, the ignition will fire in Multi-Strike mode until the engine speed exceeds 250 rpm.

Press the "NEXT" key for the next option:

Illustration 48	g00329784

Press the "ESC" key in order to exit:

Illustration 49	g00329783

Note: This feature is not available on the CIS module. The Multi-Strike special feature will appear in the display.

"Maximum Energy"

Illustration 50	g00331288

When the Maximum Energy is turned on, the ignition will fire with the maximum permissible energy until the engine speed exceeds 250 rpm. The maximum permissible energy is E3 in Single-Strike and E2 for Multi-Strike.

Press the "NEXT" key for the next option:

Illustration 51	g00329784

Press the "ESC" key in order to exit:

Illustration 52	g00329783

Note: This feature is not available on the CIS module. The special feature will appear in the display.

"Value Protection"

Enabling and disabling of the "VALUE PROTECTION" is done in the next menu. When the protection is on, none of the settings in the EEPROM can be changed. This feature can be used in order to provide limited protection from random changes by inexperienced operators.

Begin at the following screen:

Illustration 53	g00331289

Press the up arrow in order to turn on the protection:

Illustration 54	g00329780

Press the down arrow in order to turn off the protection:

Illustration 55	g00329782

Press the "NEXT" key for the next option:

Illustration 56	g00329784

Press the "ESC" key in order to exit:

Illustration 57	g00329783

"Configuration Comments"

The next screen can be used in order to view any comments that were written down during the configuration. The comments describe the configuration of the ignition system. There are a total of 8 screens which can be rotated.

Note: The EEPROM can be reconfigured with the Altronic software. The comments should be viewed in order to verify the configuration of the ignition before operation.

Begin at the following screen:

Illustration 58	g00331290

From the home screen which displays the "VIEW IGN. CONFIG" message, press the "ENTER" key in order to view the configurations:

Illustration 59	g00329851

Press the "NEXT" key for the next option:

Illustration 60	g00329784

Press the "ESC" key in order to exit:

Illustration 61	g00329783

The following types of screens can be viewed by pressing the "ENTER" key. Press the "NEXT" key in order to scroll through following screens:

Illustration 62	g00331292
Engine Application

Illustration 63	g00331332
Description Of Ignition

Illustration 64	g00331333
Date Of Application And Programmer

Illustration 65	g00331334
Firing Order And Notes From The Application

Illustration 66	g00331336
The Cylinder's Firing Order Converted To The Primary Connector Pin From One Through Six.

Illustration 67	g00331337
The Cylinder's Firing Order Converted To The Primary Connector Pin For Nine Through Twelve, Fifteen, And Sixteen.

Illustration 68	g00331338
The Cylinder's Firing Order Converted To The Primary Connector Pin For Seven, Eight, Thirteen, And Fourteen.

Illustration 69	g00331339
User's Comments

Diagnostics For The Ignition System

Diagnostic Faults

A diagnostic fault represents the most severe classification of problems. The presence of a diagnostic fault will inhibit the ignition from firing. When a fault is detected several alarms will occur:

• The ignition will stop firing.

• The alarm in the ignition unit will turn on.

• The status will indicate a "FAULT".

• The bottom of the screen will flash "VIEW DIAGNOSTICS".

Note: Diagnostic "FAULTS" will supersede diagnostic "WARNINGS".

Illustration 70	g00331548

Diagnostic Warnings

A diagnostic warning represents the least severe classification of problems. The ignition will continue to fire in the presence of a diagnostic warning. When a warning is detected several alarms will occur:

• The alarm in the ignition unit will turn on.

• The status will indicate a "WARNING".

• The bottom of the screen will flash "VIEW DIAGNOSTICS".

Illustration 71	g00331549

Diagnostic Causes

The cause of the diagnostic can be displayed for both a warning and a fault. Start at the following screen:

Illustration 72	g00331550

From the home screen which displays the "FAULT" message, press the "DIAG" key in order to view the diagnostics:

Illustration 73	g00329854

Press the "DIAG" key in order to see more diagnostics:

Illustration 74	g00329854

Press the "NEXT" key in order to see more diagnostics:

Illustration 75	g00329784

Press the "ESC" key in order to exit:

Illustration 76	g00329783

The following diagnostic faults are listed in order of priority:

When no pulses from the gear teeth are seen between the two pulses from the Hall Effect, the screen displays "GT SIGNAL FAULT NO PULSES".

Illustration 77	g00331643

When too many pulses from the gear teeth are seen without a reset pulse from the Hall Effect, the screen displays "HALL RESET FAULT NO PULSES".

Illustration 78	g00331644

When the reset signal from the TCM is missing or if the reset signal from the TCM has not been aligned properly with the signal from the Hall Effect, the screen displays "TCM RESET FAULT MISSING//NO-SINC". This diagnostic fault is activated only while the TCM is in AUTO mode.

Illustration 79	g00331645

When too many pulses or too few pulses from the gear teeth are seen between the reset pulses from the Hall Effect, the number of pulses is displayed with the "RING-GEAR FAULT" message.

Illustration 80	g00331647

When the engine speed exceeds the overspeed setpoint, the maximum speed that is observed is displayed with "ENGINE OVERSPEED".

Illustration 81	g00331649

When the checksum of the microprocessor's firmware can not be verified, the screen displays "BOTTOM BOARD UP CHECKSUM FAILED". This screen tells the operator that the unit requires service.

Illustration 82	g00331650

The following diagnostic warnings are listed in order of priority:

When incorrect data or incomplete data of the injector firing is saved in the EEPROM, the screen displays "EEPROM MEMORY CHECKSUM FAILED". The EEPROM must be reprogrammed or replaced.

Illustration 83	g00332182

When the diagnostics have identified an open circuit on the primary output "A", the screen displays "PRIMARY OPEN A". This would normally indicate faulty wiring or a failed coil.

Illustration 84	g00332183

When the diagnostics have identified a short circuit on the primary output "B", the screen displays "PRIMARY SHORT B". This would normally indicate that the primary wire was shorted to a ground.

Illustration 85	g00332184

When the diagnostics have identified a low spark demand on the spark plug in the "C" coil, the screen will display "LO SPARK VOLT C". This can be caused by a failed spark plug or a shorted secondary spark.

Illustration 86	g00332185

When the diagnostics have identified a high spark demand on the spark plug in the "D" coil, the screen will display "HI SPARK VOLT D". This is often caused by worn spark plugs.

Illustration 87	g00332186

The screen displays "NO SEC SPARK E" when no spark appears on the spark plug in the "E" coil. No spark occurred because the demand was greater than the capability of the output voltage of the coil.

Illustration 88	g00332187

After all of the diagnostics have been read, the user can reset the warnings and the faults by first pressing the "ESC" key in order to exit:

Illustration 89	g00329783

Then press the "RESET" key:

Illustration 90	g00329855

Pressing the "RESET" key performs all of the following actions:

• The reset clears all diagnostic warnings from memory.

• The reset clears all diagnostic faults from memory.

• The reset clears a shutdown condition once the ground has been corrected.

• The reset causes the temporary cylinder timing offsets to be inserted from the EEPROM.

Understanding And Using The Secondary Spark Diagnostics

The spark reference number is a number which correlates with the demand for voltage at the spark plug. The reference number is calculated for ever firing of each cylinder. As the voltage increases, the reference number also increases. The number will increase faster at voltages above 20 kV. The usefulness of the number is not in the absolute value. The number changes over time as the spark plugs erode. This change in the number's value will give the pertinent information. With a little experience, the engine operator will be able to determine when the spark plugs require changing. Abnormal conditions in the ignition system can also be detected.

This reference number can be viewed in two ways:

• An instantaneous value

• An average value

The average number will be more useful for most purposes.

Start at the following screen:

Illustration 91	g00332296

From the screen which displays the "FIRING" message, press the "F1" key in order to view the data from the secondary spark:

Illustration 92	g00329856

The instantaneous number and the average for output "A" is displayed on the next screen:

Illustration 93	g00332295

Use the "F1" key in order to view the next cylinder's data:

Illustration 94	g00329856

Use the "NEXT" key in order to view the next cylinder's data:

Illustration 95	g00329784

Press the "ESC" key in order to exit:

Illustration 96	g00329783

The spark reference number is used in conjunction with the comparative thresholds in order to set diagnostic codes for several conditions in the ignition system and the spark plug. A diagnostic sensor must be flagged twice in order to avoid acting on the data of only one firing sequence. The reference number is compared to the following thresholds:

• An "Open Primary" is less than one.

• A "Shorted Primary" is less than 40.

• A "Low Spark Voltage" is less than the user's programmable threshold (default 60).

• A "No Secondary Spark" is greater than the user's programmable threshold (default 200).

• A "High Spark Voltage" is greater than the user's programmable threshold (default 180).

The average value is used in order to compare the reference number against the programmable thresholds. When a threshold is violated twice in a row, the corresponding diagnostic flag is set for the appropriate cylinder. The diagnostic flags will exist until the unit is restarted. The diagnostic flags will also be removed when a reset or a powerdown occurs.

The adjustment of the programmable thresholds is based on the type of coil that is being used. The adjustment of the thresholds is also based on the operating characteristics of the engine and the demand for voltage. There are known differences between various types of Altronic coils. Slight variations are normal between the same type of coils. In order to maximize the usefulness of the cylinder's spark reference number, use the same type of coil which was produced on the same date. This will aid greatly in detecting variations in one cylinder versus the general trend in the engine. The threshold range that is expected while you are operating new spark plugs under normal conditions is 120 to 140.

The indicated thresholds were designed to be adjustable so that the user can customize these diagnostics in order to equip the specific needs of each engine. Customizing the thresholds will take testing and adjustment in order to obtain thresholds that optimize the use of these features. The spark reference number for each cylinder should be recorded at the normal operating load when new spark plugs are installed. The reference number should then be monitored over a period of time for changes. The "HI SPARK VOLTAGE" alarm should be set at 180 initially. The level of the alarm can be adjusted as experience dictates. A gradual increase in the reference number is expected over time as the spark plug electrodes erode.

In addition to the diagnostic flags, the reference numbers can also be used in order to predict possible failures.

1. As the numbers increase toward the preset "HI SPARK VOLTAGE" threshold, the operator knows that a change of spark plugs should be scheduled. With this information, maintenance on the spark plugs can be based on an actual need rather than a predetermined schedule. Unexpected misfiring of the engine and shutdowns can be avoided by routine tracking of the reference numbers.

2. The reference numbers can provide an early warning of a difference in operation in a given cylinder. A change in the readings alerts the operator to a potential problem. This allows further troubleshooting and analyzing to take place before an unexpected operational problem develops.

The following Steps outline the procedure for viewing and adjusting the low voltage's threshold:

Begin at the following screen:

Illustration 97	g00332296

From the home screen which displays the "FIRING" message, press the "F2" key in order to view the low voltage's data:

Illustration 98	g00329857

Continue from the following screen:

Illustration 99	g00332297

Note: The factory setting is at 60. Adjust the setting for the low voltage to 0 in order to disable this diagnostic feature.

Press the up arrow in order to increase the threshold:

Illustration 100	g00329780

Press the down arrow in order to decrease the threshold:

Illustration 101	g00329782

Press the "F2" key in order to view the high voltage threshold:

Illustration 102	g00329857

Press the "NEXT" key in order to view the high voltage threshold:

Illustration 103	g00329784

Press the "ESC" key in order to exit:

Illustration 104	g00329783

Continue from the following screen:

Illustration 105	g00332298

Note: The factory setting is at 200. Adjust the high voltage's setting to 255 in order to disable this diagnostic feature.

Press the up arrow in order to increase the threshold:

Illustration 106	g00329780

Press the down arrow in order to decrease the threshold:

Illustration 107	g00329782

Press the "F2" key in order to view the "NO SECONDARY SPARK" threshold:

Illustration 108	g00329857

Press the "NEXT" key in order to view the "NO SECONDARY SPARK" threshold:

Illustration 109	g00329784

Press the "ESC" key in order to exit:

Illustration 110	g00329783

Continue from the following screen:

Illustration 111	g00332299

Note: The factory setting is at 250. Adjust the "NO SECONDARY SPARK" setting to 255 in order to disable this diagnostic feature.

Press the up arrow in order to increase the threshold:

Illustration 112	g00329780

Press the down arrow in order to decrease the threshold:

Illustration 113	g00329782

Press the "F2" key in order to view the "LO SPARK VOLTAGE" threshold:

Illustration 114	g00329857

Press the "NEXT" key in order to view the "LO SPARK VOLTAGE" threshold:

Illustration 115	g00329784

Press the "ESC" key in order to exit:

Illustration 116	g00329783

The following instruction is additional information regarding the spark reference number:

• The setting of the energy level has only a small effect on the reference number if the spark plug fires correctly. Therefore, the thresholds for the high voltage and the threshold for the low voltage should remain in place if the spark plugs fire correctly. On the other hand, a worn spark plug may not fire consistently on E1. A worn spark plug will fire consistently on E2. In this case, there will be a significant difference in the reference number when the level of energy is changed. Operators may be able to increase the spark plug's life by operating initially with new spark plugs on E1. The "HI SPARK VOLTAGE" alarm should then be used as an indicator to increase the energy progressively to E3.

• The spark reference number is designed to work with one coil per output. When two coils are connected to the same primary lead, the reference number will tend to be an average of the conditions at the two spark plugs. While some of the benefits of the reference number can still be realized, the ability of the number to detect the deviation between the cylinders will be reduced.