3500B Series II Marine Engines Caterpillar

System Operation Description:

The Electronic Control Module (ECM) has the ability to stop the engine by shutting off the inlet air supply in an emergency situation. The ECM activates the output driver for the emergency shutdown system. The "ASOS" switch energizes the two air shutoff solenoids. The solenoids trip the air shutoff valves.

There are two conditions which cause the engine control to activate the output driver for the air shutoff switch. The first condition occurs when the operator activates the customer's emergency stop. When the customer's emergency stop button is activated, the emergency stop inputs U and T to the ECM from the customer connector go high. The ECM will recognize this change. The ECM will energize the output drive for the emergency shutdown system for one second through the diode assembly.

The second condition occurs for an engine overspeed. If an engine overspeed occurs, the ECM will activate the "ASOS" switch for the emergency shutdown system through the diode assembly.

Relay "R3A" and relay "R3" are energized at the same time as the "ASOS" switch through terminal 3 of the diode assembly. Terminal 3 of the diode assembly will energize relay "R3A" and relay "R3" for one second. The contacts of relay "R3" keeps relay "R3A" and relay "R3" energized until power is cycled. The contact of relay "R3A" keeps the coil of relay "R2A" energized. When relay "R2A" is energized, power is removed from the ECM. The ECM will power down. The injection signals to the injector solenoids will stop.

The contact of relay "R3A" also supplies power to terminal 3 of the connector for a timer and to the overspeed indicator on the instrument panel. When power is applied to terminal 3 of the connector for the timer, the timer will activate. The timer outputs 24 VDC from terminal 6 of the connector for the timer for 2.5 seconds. The 24 VDC from the timer is applied to the coil of the "ASOS" switchand to terminal 2 of the diode assembly. The "ASOS" switch energizes the two air shutoff solenoids. The solenoids trip the air shutoff valves. The 2.5 second time limit for activation of the "ASOS" switch prevents damage to the air shutoff solenoids. A normally closed switch at the air shutoff valves will open when the air shutoff solenoid activates the air shutoff valve. The switch input to the ECM notifies the ECM that the air shutoff valves are closed. The ECM will not send injection signals to the injector solenoids until the switch inputs from the air shutoff valves indicate that the valves are open.

An overspeed can be simulated by using the Caterpillar Electronic Technician (ET). In order to verify that the overspeed function is operable, the operator must access the screen for overriding parameters on Cat ET. When the override for the engine overspeed is set to the ON position, the setpoint for the engine overspeed is at 75 percent of the original setpoint. When the engine reaches the modified setpoint, the normal strategy for an engine overspeed is initiated.

The engine is equipped with a redundant overspeed circuit. The circuit consists of a magnetic pickup that sends a pulsed signal to a speed switch. When an overspeed condition occurs, the speed switch detects the overspeed by monitoring the signal from the magnetic pickup. The speed switch will close a set of normally open contacts. The contacts will energize relay "R3A" and relay "R3". The overspeed indicator light on the instrument panel will illuminate. The contacts of relay "R3" keeps relay "R3A" and relay "R3" energized until power is cycled. The contact of relay "R3A" keeps the coil of relay "R2A" energized. When relay "R2A" is energized, power is removed from the ECM. The ECM will power down. The injection signals to the injector solenoids will stop.

The "ASOS" switch can be activated independently of the sourcing driver of the ECM. When the local emergency stop switch on the instrument panel is depressed or the remote emergency stop switch is activated, the coils of relay "R4" and relay "R4A" are energized. The contacts of relay "R4A" supplies power to terminal 3 of the connector for the timer and to the coil of relay "R2A". When relay "R2A" is energized, power is removed from the ECM. The circuit will operate in the same manner that was described above except that the emergency stop lamp on the instrument panel will illuminate and the relays "R3A" and "R3" will de-energize after 2.5 seconds. When relays "R3A" and "R3" de-energize, the overspeed indicator turns off.

Regardless of the reason for activation, the Engine Control Switch (ECS) must be turned to the OFF/RESET position for three seconds. This resets the ECM and the relays in the circuit. In addition to turning the ECS to the OFF/RESET position, the operator must determine the cause for the emergency shutdown before resetting the circuit. The operator must manually open the air shutoff valves before restarting the engine.

Illustration 1	g01199226
Typical example

Test Step 1. Check for Connector Damage

1. Verify that the circuit breakers are not tripped.

2. Turn the circuit breaker for the battery to the OFF position.

3. Turn the ECS to the OFF/RESET position.

4. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.

5. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.

6. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct torque values.

7. Check the harness and the wiring for abrasion and for pinch points.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion, and of pinch points.

Results:

• OK - The connectors and wiring are OK. Proceed to Test Step 2.

• Not OK - The connectors and/or wiring are not OK.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

Test Step 2. Test the Air Shutoff System

1. Turn the circuit breaker for the battery to the ON position.

2. Turn the ECS to the STOP position. The engine should be off.

3. Activate the customer's emergency stop switch.

4. Monitor the air shutoff solenoids.

5. Deactivate the customer's emergency stop switch.

Expected Result:

The air shutoff solenoids activated.

Results:

• OK - The air shutoff solenoids activated correctly.

  Repair: The problem may be intermittent. If the problem is intermittent, refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".

  STOP

• Not OK - The air shutoff solenoids failed to activate. Proceed to Test Step 3.

Test Step 3. Check for the Signal from the "ASOS" Switch at the Connector P-C1 for the Power Distribution Panel

1. Turn the ECS to the STOP position. The engine should be off.

2. Activate the customer's emergency stop switch.

3. Monitor the voltage on wire G708 on pin I at connector P-C1 of the rigid harness.

4. Deactivate the customer's emergency stop switch.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds. The circuit is operating correctly to this point. Proceed to Test Step 7.

• Not OK - The voltage did not measure 24 ± 3 VDC for approximately 2.5 seconds. Proceed to Test Step 4.

Test Step 4. Test for Voltage to the Coil of the "ASOS" Switch at the Connector P-C1 for the Power Distribution Panel

1. Turn the ECS to the STOP position. The engine should be off.

2. Activate the customer's emergency stop switch.

3. Monitor the voltage on wire F708 on pin G at connector P-C1 of the rigid harness.

4. Deactivate the customer's emergency stop switch.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately one second.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately one second. The circuit is operating correctly to this point. Proceed to Test Step 5.

• Not OK - No voltage was measured. Proceed to Test Step 14.

Test Step 5. Test for Voltage to the Coil of the "ASOS" Switch

1. Turn the ECS to the OFF/RESET position.

2. The input to the coil of the "ASOS" switch is wire T708 from the diode assembly. Connect a voltmeter between wire T708 on the "ASOS" switch and the engine ground.

   Note: The "ASOS" switch is turned on for one second by the ECM. The timer keeps the "ASOS" switch energized for approximately 2.5 seconds.

3. Turn the ECS to the STOP position. The engine should be off.

4. Activate the customer's emergency stop switch.

5. Monitor the voltage on the voltmeter.

6. Deactivate the customer's emergency stop switch.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds. The circuit is operating correctly to this point. Proceed to Test Step 6.

• Not OK - No voltage was measured. Proceed to Test Step 10.

• Not OK - The voltage did not measure 24 ± 3 VDC for 2.5 seconds. Proceed to Test Step 8.

Test Step 6. Check for Voltage from the "ASOS" Switch to the Air Shutoff Solenoids

1. Turn the ECS to the OFF/RESET position.

2. Disconnect wire G708 from the "ASOS" switch.

3. Connect a voltmeter to the empty terminal on the "ASOS" switch. Connect the other lead of the voltmeter to engine ground.

4. Turn the ECS to the STOP position. The engine should be off.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Reconnect wire G708 to the "ASOS" switch.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds. The circuit is operating correctly to this point.

  Repair: Repair the wire G708 between the "ASOS" switch and terminal I at connector P-C1 of the rigid harness.

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC for approximately 2.5 seconds.

  Repair: Verify that 24 ± 3 VDC is present on wire K708 at the normally open contacts of the "ASOS" switch. If voltage is not present on wire K708, check the wiring and the circuit breaker for the air shutoff for problems.Check wire 220 on the coil of the "ASOS" switch for continuity to the −Battery. If necessary, repair the wire or replace the wire.If wire 220 is OK and voltage is present on wire K708, replace the "ASOS" switch.

  STOP

Test Step 7. Check the Voltage at the Connector for the Air Shutoff Solenoids

1. Turn the ECS to the OFF/RESET position.

2. Disconnect the connector for the air shutoff solenoids. Disconnect the connector for the right and left sides of the engine.

3. Connect a voltmeter between wire G708 on the connector for the air shutoff solenoid and the engine ground.

4. Turn the ECS to the STOP position. The engine should be off.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Reconnect the connectors for the air shutoff solenoids.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds. The circuit is operating correctly to this point.

  Repair: Check the wire H708 from terminal A of the connectorfor the air shutoff solenoid for continuity to the −Battery terminal. If the wire H708 to the −Battery terminal is OK, replace the air shutoff solenoid.

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC for approximately 2.5 seconds. System voltage was not available at the solenoid connector.

  Repair: Repair the wire G708 between the connector for the air shutoff solenoids and terminal I at connector P-C1 of the rigid harness.

  STOP

Test Step 8. Check the Voltage at the Contact of Relay "R3A"

1. Turn the ECS to the OFF/RESET position.

2. Disconnect wire T120 from terminal 87 of relay "R3A".

3. Connect a voltmeter between terminal 87 of relay "R3A" and the engine ground.

4. Turn the ECS to the STOP position. The engine should be off.

5. Activate the customer's emergency stop switch.

6. Monitor the voltage on the voltmeter.

7. Deactivate the customer's emergency stop switch.

8. Reconnect wire T120.

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 9.

• Not OK - The voltage did not measure 24 ± 3 VDC. Proceed to Test Step 11.

Test Step 9. Check the Voltage at Terminal 6 of the Connector for the Timer

1. Turn the ECS to the OFF/RESET position.

2. Connect a voltmeter between terminal 6 of the connector for the timer and engine ground.

3. Turn the ECS to the STOP position. The engine should be off.

4. Activate the customer's emergency stop switch.

5. Monitor the voltage on the voltmeter.

6. Deactivate the customer's emergency stop switch.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds. Proceed to Test Step 12.

• Not OK - The voltage did not measure 24 ± 3 VDC for approximately 2.5 seconds.

  Repair: Check for 24 ± 3 VDC on terminal 3 of the connector for the timer. If voltage is not present on terminal 3, repair the wire T120 between terminal 87 of relay "R3A" and terminal 3 of the connector for the timer.If voltage is present on terminal 3 of the connector for the timer, verify that wire 220 on terminal 2 of the connector for the timer has continuity to the −Battery. If wire 220 does not have continuity to the −Battery, repair the wire. Verify that 24 ± 3 VDC is present on terminal 1 of the connector for the timer. If 24 ± 3 VDC is not present on terminal 1 of the connector for the timer, verify that the engine control switch is not in the "OFF/RESET" position. Verify that the "MPD" breaker is not tripped. Check the normally closed contact of relay "R1" for proper operation. Check the wire 120 between terminal 1 of the connector for the timer and relay "R1" for damage. Check the wire A120 between relay "R1" and the "MPD" breaker for damage. If necessary, repair the wires.If the voltage is present on terminal 3 and 1 of the timer and wire 220 is OK, replace the timer.

  STOP

Test Step 10. Check the Voltage at Terminal 4 of the Connector for the Diodes

1. Turn the ECS to the OFF/RESET position.

2. Connect a voltmeter between terminal 4 of the connector for the diodes and the engine ground.

3. Turn the ECS to the STOP position. The engine should be off.

4. Activate the customer's emergency stop switch.

5. Monitor the voltage on the voltmeter.

6. Deactivate the customer's emergency stop switch.

Expected Result:

The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for approximately 2.5 seconds.

  Repair: Repair the wire T708 between the connector for the diodes and the "ASOS" switch.

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC for approximately 2.5 seconds.

  Repair:

  1. Turn the ECS to the OFF/RESET position.

  2. Connect a voltmeter between terminal 1 of the connector for the diodes and the engine ground.

  3. Turn the ECS to the STOP position. The engine should be off.

  4. Activate the customer's emergency stop switch.

  5. Monitor the voltage on the voltmeter.

  6. Deactivate the customer's emergency stop switch.
  If the voltage measures 24 ± 3 VDC for approximately one second, replace the diodes.If the voltage does not measure 24 ± 3 VDC for approximately one second, repair the wire F708 between the connector for the diodes and wire F708 on pin G at connector P-C1 of the right rail.

  STOP

Test Step 11. Check the Voltage at the Coil of Relay "R3A"

1. Turn the ECS to the OFF/RESET position.

2. Connect a voltmeter between wire 918 on terminal 86 of relay "R3A" and the engine ground.

3. Turn the ECS to the STOP position. The engine should be off.

4. Activate the customer's emergency stop switch.

5. Monitor the voltage on the voltmeter.

6. Deactivate the customer's emergency stop switch.

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC.

  Repair: Check wire 220 on the coil of the "R3A" relay for continuity to the −Battery. If necessary, repair the wire or replace the wire.Check for 24 ± 3 VDC on wire 120 on terminal 30 of relay "R3A". If 24 ± 3 VDC is not present on wire 120, verify that the engine control switch is not in the "OFF/RESET" position. Verify that the "MPD" breaker is not tripped. Check the normally closed contact of relay "R1" for proper operation. Check the wire 120 between terminal 30 of the relay "R3A" and relay "R1" for damage. Check the wire A120 between relay "R1" and the "MPD" breaker for damage. If necessary, repair the wires.If wire 220 is OK and voltage is present on wire 120 on terminal 30, replace relay "R3A".

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC. Proceed to Test Step 13.

Test Step 12. Check the Voltage to Terminal 2 of the Connector for the Diodes from the Timer

1. Turn the ECS to the OFF/RESET position.

2. Connect a voltmeter between the terminal 2 of the connector for the diodes and the engine ground.

3. Turn the ECS to the STOP position. The engine should be off.

4. Activate the customer's emergency stop switch.

5. Monitor the voltage on the voltmeter.

6. Deactivate the customer's emergency stop switch.

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 13.

• Not OK - The voltage did not measure 24 ± 3 VDC.

  Repair: Repair the wire T708 between the diodes and the timer.

  STOP

Test Step 13. Check the Voltage from Terminal 3 of the Connector for the Diode Assembly

1. Turn the ECS to the OFF/RESET position.

2. Connect a voltmeter between terminal 3 of the connector for the diode assembly and the engine ground.

3. Turn the ECS to the STOP position. The engine should be off.

4. Activate the customer's emergency stop switch.

5. Monitor the voltage on the voltmeter.

6. Deactivate the customer's emergency stop switch.

Expected Result:

The voltage measures 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC.

  Repair: Repair the wire 918 between the diodes and relay "R3A".

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC.

  Repair: Replace the diodes.

  STOP

Test Step 14. Check the Output Driver for the Air Shutoff System at the ECM

1. Turn the ECS to the OFF/RESET position.

2. Disconnect the ECM connector J2.

3. Remove wire F708 from ECM connector P2-13. Install a wire jumper into P2-13.

4. Reconnect ECM connector P2.

5. Connect a voltmeter between the wire jumper in P2-13 and engine ground.

6. Turn the ECS to the STOP position. The engine should be off.

7. Activate the customer's emergency stop switch.

8. Monitor the voltage on the voltmeter.

9. Deactivate the customer's emergency stop switch.

Expected Result:

The voltage measures 24 ± 3 VDC for one second.

Results:

• OK - The voltage measures 24 ± 3 VDC for one second.

  Repair: Repair the wire F708 between the ECM connector and terminal G at connector P-C1 of the rigid harness.

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC.

  Repair: Replace the ECM.

  STOP