3500B and 3500B High Displacement Generator Set Engines Caterpillar


Electrical Power Supply (EMS II)

Usage:

3508B 5KW
System Operation Description:

A signal from the Engine Control Switch (ECS) is provided to the key switch input of the engine's Electronic Control Module (ECM) that tells the ECM the position of the ECS. When the ECM senses battery voltage to the key switch input of the ECM, the ECM will power up. The key switch input receives battery voltage when the ECS is in the REMOTE, LOCAL or SERVICE positions. If the voltage is removed from the key switch input, the ECM will power down. Cycling power to the key switch input of the ECM will reset the ECM and all active engine diagnostic codes.

The electrical power for the engine ECM comes through a 15 amp circuit breaker to the battery terminals on the ECM. The presence of two +Battery connections and two -Battery connections to the ECM reduces harness resistance. All of these connections must be complete in order to ensure proper engine operation.

The electrical power for the EMS II is provided by the 40 amp "EMCP II" circuit breaker and the 10A fuse F1.




Illustration 1g01023335

Typical circuit with EMS II

Test Step 1. Check for Connector Damage.

  1. Turn the ECS to the OFF position.

  1. Turn the battery disconnect switch to the OFF position.

  1. 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.

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

  1. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

  1. Check the customer connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).

  1. 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 is free of corrosion, of abrasion or of pinch points.

Results:

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

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

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

    Stop.

Test Step 2. Check the Voltage to the ECM.

  1. Remove ECM connector J1/P1.

  1. Turn the battery disconnect switch to the ON position.

  1. Turn the ECS to the SERVICE position.

  1. Measure the voltage between P1-6 and P1-5.

  1. Measure the voltage between P1-4 and P1-11.

  1. Measure the voltage between P1-23 and P1-11.

  1. Turn the ECS to the OFF position.

  1. Turn the battery disconnect switch to the OFF position.

  1. Reconnect ECM connector J1/P1.

Expected Result:

The voltage is 24 ± 3 VDC.

Results:

  • OK - The voltage is 24 ± 3 VDC at P1-4, P1-6 and P1-23. The ECM is receiving the correct voltage. Proceed to Test Step 8.

  • Not OK - The voltage is not 24 ± 3 VDC at P1-4 and P1-6. The battery or the alternator may be causing the problem. Proceed to Test Step 3.

  • Not OK - ECM Keyswitch - The voltage is not 24 ± 3 VDC at P1-23. Proceed to Test Step 4.

Test Step 3. Check the Battery Voltage.

  1. Measure the open circuit voltage at the battery terminals. Refer to Testing and Adjusting, "Test Tools for the Electrical System" for the proper procedures to check the batteries.

  1. Load test the batteries. Use the 4C-4911 Battery Load Tester. Refer to the Operating Manual, SEHS9249. Refer to Special Instruction, SEHS7633.

Expected Result:

The open circuit voltage at the batteries is at least 24 ± 1 VDC, and the batteries pass the load test.

Results:

  • OK - The open circuit voltage at the batteries is 24 ± 1 VDC, and the batteries pass the load test.

    Repair: There is a problem in the harness. Repair the connectors and/or wiring or replace the connectors and/or wiring between the battery and the ECM.

    Stop.

  • Not OK - The battery voltage is incorrect and/or the battery fails the load test.

    Repair: The batteries or the alternator are causing the problem. Recharge the batteries or replace the batteries. Verify that the original condition is resolved. Refer to Testing and Adjusting, "Electrical System".

    Stop.

Test Step 4. Check the Voltage to the ECS.

  1. Turn the battery disconnect switch to the ON position.

  1. Turn the ECS to the SERVICE position.

  1. Measure the voltage between terminal 1 of the ECS and the -Battery terminal.

  1. Turn the ECS to the OFF position.

  1. Turn the battery disconnect switch to the OFF position.

Expected Result:

The voltage is 24 ± 3 VDC.

Results:

  • OK - The voltage is 24 ± 3 VDC. Proceed to Test Step 5.

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

    Repair: Verify that fuse F1 is not blown. Verify that the circuit breaker "EMCP II" is not tripped. Check the wires and connectors from the ECS to the +Battery terminal for continuity. If necessary, repair any wires and/or connectors.

    Stop.

Test Step 5. Check the Voltage at the Coil of the "SR" Relay.

  1. Turn the battery disconnect switch to the ON position.

  1. Turn the ECS to the SERVICE position.

  1. Measure the voltage between terminal 2 of the "SR" relay and the -Battery terminal.

  1. Turn the ECS to the OFF position.

  1. Turn the battery disconnect switch to the OFF position.

Expected Result:

The voltage is 24 ± 3 VDC.

Results:

  • OK - The voltage is 24 ± 3 VDC. Proceed to Test Step 6.

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

    Repair: Check for 24 ± 3 VDC on terminal 5 of the ECS. If voltage is present on terminal 5 of the ECS, repair the wire 3A between the ECS and the "SR" relay.If voltage is not present on terminal 5 of the ECS, replace the ECS.

    Stop.

Test Step 6. Check the Voltage to the Normally Open Contacts of the "SR" Relay.

  1. Turn the battery disconnect switch to the ON position.

  1. Turn the ECS to the SERVICE position.

  1. Measure the voltage between terminal 1 of the "SR" relay and the -Battery terminal.

  1. Turn the ECS to the OFF position.

  1. Turn the battery disconnect switch to the OFF position.

Expected Result:

The voltage is 24 ± 3 VDC.

Results:

  • OK - The voltage is 24 ± 3 VDC. Proceed to Test Step 7.

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

    Repair: Repair the wire between terminal 1 of the ECS and terminal 1 of the "EM".

    Stop.

Test Step 7. Check the Voltage from the Normally Open Contacts of the "SR" Relay.

  1. Turn the battery disconnect switch to the ON position.

  1. Turn the ECS to the SERVICE position.

  1. Measure the voltage between terminal 3 of the "SR" relay and the -Battery terminal.

  1. Turn the ECS to the OFF position.

  1. Turn the battery disconnect switch to the OFF position.

Expected Result:

The voltage is 24 ± 3 VDC.

Results:

  • OK - The voltage measures 24 ± 3 VDC.

    Repair: There is an open between the normally open contacts and the ECM. Repair the connectors and/or wiring or replace the connectors and/or wiring.

    Stop.

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

    Repair: Check the wire 2 from terminal 10 of the "SR" relay for continuity to the -Battery. If the wire has an open, repair the wire. If wire 2 is okay, replace the "SR" relay. Verify that the circuit is operating correctly.

    Stop.

Test Step 8. Check the Voltage at the Sensor Power Supplies.

  1. Disconnect ECM connector J1/P1.

  1. Remove the following wires from ECM connector P1. Install a wire jumper for each of the following wires that are removed.

    • P1-36 analog power 997-OR

    • P1-30 analog return 993-BR

    • P1-35 digital power A700-OR

    • P1-29 digital return 998-BR

  1. Reconnect ECM connector J1/P1.

  1. Turn the battery disconnect switch to the ON position.

  1. Turn the ECS to the SERVICE position.

  1. Measure the voltage from the analog sensor supply P1-36 to the analog sensor return P1-30.

  1. Measure the voltage from digital sensor supply P1-35 to the digital sensor return P1-29.

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

  1. Turn the battery disconnect switch to the OFF position.

  1. Remove the wire jumpers. Replace all wires.

Expected Result:

The voltage is 5.0 ± 0.2 VDC between P1-36 and P1-30. The voltage is 8.0 ± 0.4 VDC between P1-35 and P1-29.

Results:

  • OK - The sensor power supplies are functioning properly. The ECM is powered up. The problem is not in the electrical system.

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

    Stop.

  • Not OK - If the ECM is getting the correct voltage at the +Battery terminal, but the ECM does not supply the correct voltages to the sensors, replace the ECM.

    Repair: Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".

    Stop.

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