C15 Petroleum Engines Caterpillar

Use this procedure in order to troubleshoot the air shutoff system or use this procedure if another procedure has sent you here.

This procedure checks the circuits for the air shutoff system. The Electronic Control Module (ECM) does not provide diagnostics for the circuits that are for the air shutoff system.

There are two conditions which can cause the ECM to activate the air shutoff:

Engine Overspeed - The first condition occurs when the ECM detects an engine overspeed condition. The ECM energizes the air shutoff solenoid and the fuel injection is disabled. The air shutoff system is latched by the ECM until the keyswitch is cycled.

System test - The second condition occurs when a test of the air shutoff system is performed. The overspeed verify that switch can be activated by the operator in order to perform this test. The engine speed is then increased to 75 percent of the programmed overspeed setpoint. The ECM activates the air shutoff system as the engine speed exceeds 75 percent of the programmed overspeed setpoint. The ECM energizes the air shutoff solenoid and fuel injection is disabled. The air shutoff system is latched by the ECM until the keyswitch is cycled.

Note: If the "Air Shutoff" parameter is set to "Not Installed", the functionality for the overspeed verify that the switch remains operational. If the switch is activated during engine operation, the ECM will disable injection for any engine speed over 75 percent of the programmed overspeed setpoint. As the engine speed drops below 75 percent of the programmed overspeed setpoint, the injection is again enabled by the ECM. This functionality is not latched by the ECM and the functionality is disabled when the switch is turned off.

For some air shutoff systems, after the air shutoff mechanism has been tripped, a manual reset of the mechanism may be necessary.

Note: A momentary switch is recommended since many relays and solenoids are not rated for continuous duty and may be damaged if the switch stays closed for an extended period. Check to make sure that the solenoid is working properly.

Illustration 1	g02564279
Schematic for the (S/N: HAZ) ATEX air shutoff system

Illustration 2	g02576957
Schematic for the standard (S/N: SWE) air shutoff system

Show/hide table

The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere.

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Remove the electrical power from the ECM.

2. Verify that the air shutoff mechanisms are set to the OPEN position.

Show/hide table



Illustration 3	g02544741
ECM connectors (typical example) (1) J1/P1 ECM connectors

Show/hide table



Illustration 4	g02546496
Air shutoff mechanism S/N Prefix HAZ (typical example) (2) Air shutoff solenoid

Show/hide table



Illustration 5	g01210157
Air shutoff mechanism S/N Prefix SWE (typical example) (3) Terminals for the air shutoff solenoid

3. Thoroughly inspect connectors (1) and (2). Also, thoroughly inspect connections (3) at the air shutoff solenoid. Refer to Troubleshooting, "Electrical Connectors - Inspect".

Show/hide table



Illustration 6	g01212804
P1 terminals for the air shutoff system (P1-11) Air shutoff relay (P1-54) Overspeed verify switch (P1-67) Return

4. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the air shutoff system.

5. Check the allen head screw on each ECM connector for the proper torque. Also, check the allen head screw on the customer connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

6. Check the harness and the wiring for abrasion and for pinch points from the air shutoff solenoid to the ECM.

Expected Result:

All connectors, pins, and sockets are 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 appear to be OK. Proceed to Test Step 2.

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

  Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. Verify that the problem is resolved.

  STOP

Test Step 2. Test the Operation of the Control Solenoid for the Air Shutoff Relay

1. Remove the electrical power from the ECM.

Show/hide table



Illustration 7	g02577176
Location of the test lamp

2. Remove the wire from the output of the air shutoff relay.

3. Connect a test lamp between the output of the solenoid for the air shutoff relay and engine ground.

4. Start the engine.

5. Activate the overspeed verify switch.

6. Monitor the test lamp while you increase the engine speed past 75 percent of the programmed overspeed setpoint.

7. Stop the engine.

8. Remove the test lamp from the circuit. Restore the wiring to the original configuration.

Expected Result:

The test lamp illuminated when the engine speed increased past 75 percent of the programmed overspeed setpoint.

Results:

• OK - The test lamp illuminated. The air shutoff relay is operating correctly. Proceed to Test Step 3.

• Not OK - The test lamp did not illuminate. No voltage is present at the output of the relay. Proceed to Test Step 4.

Test Step 3. Test for Voltage at the Air Shutoff Solenoid

1. Remove the electrical power from the ECM.

Show/hide table



Illustration 8	g02577197
Location of the test lamp

2. Disconnect the wire from the positive terminal of the air shutoff solenoid.

3. Connect a test lamp between the wire for the positive terminal of the air shutoff relay and engine ground.

4. Start the engine.

5. Activate the overspeed verify switch.

6. Monitor the test lamp while you increase the engine speed past 75 percent of the programmed overspeed setpoint.

7. Stop the engine.

Expected Result:

The test lamp illuminated when the engine speed increased past 75 percent of the programmed overspeed setpoint.

Results:

• OK - The test lamp illuminated.

  Repair: The voltage is present at the air shutoff solenoid. Check for continuity of the ground circuit for the air shutoff solenoid before proceeding. If the ground circuit is OK, replace the air shutoff solenoid. Verify that the problem is resolved.

  STOP

• Not OK - The test lamp did not illuminate.

  Repair: System voltage was not present at the air shutoff solenoid. There is a problem in the wiring between the output of the air shutoff relay and the input of the air shutoff solenoid. There may be a problem in a connector. Repair the wiring and/or the connector. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 4. Test the Control Input Voltage at the Air Shutoff Relay

1. Remove the electrical power from the ECM.

2. Disconnect the wires from the control input of the air shutoff relay at the relay.

3. Connect the test lamp between the two control wires.

4. Start the engine.

5. Activate the overspeed verify switch.

6. Monitor the test lamp while you increase the engine speed past 75 percent of the programmed overspeed setpoint.

7. Stop the engine.

Expected Result:

The test lamp illuminated when the engine speed increased past 75 percent of the programmed overspeed setpoint.

Results:

• OK - The test lamp illuminated. Control input voltage is reaching the relay. Proceed to Test Step 6.

• Not OK - The test lamp did not illuminate. The voltage from the ECM was not present at the coil of the air shutoff relay. Restore the wiring to the original configuration. Proceed to Test Step 5.

Test Step 5. Check the Output Voltage for the Air Shutoff Relay at the ECM

1. Remove the electrical power from the ECM.

2. Disconnect the P1 ECM connector.

3. Fabricate a jumper wire that is long enough to reach from the P1-54 ECM connector to engine ground. Crimp a connector socket to one end of the jumper wire.

4. Remove the wire from terminal location P1-54 (overspeed verify switch) at the ECM connector. Insert the jumper wire into this terminal location.

5. Fabricate two other jumper wires that can be used as test leads at the ECM connector. Crimp a connector socket to one end of each jumper wire.

6. Remove the wires from terminal locations P1-11 (air shutoff solenoid) and P1-67 (solenoid return) at the ECM connector. Insert one of the jumper wires into each of these terminal locations.

7. Connect the J1/P1 ECM connectors.

8. Connect the loose end of the jumper wire that is in terminal location P1-54 to the engine ground stud.

9. Connect the leads of the voltage test lamp to the loose ends of the other two jumper wires that are in the P1 ECM connector.

10. Start the engine.

11. Monitor the test lamp while you increase the engine speed past 75 percent of the programmed overspeed setpoint.

12. Stop the engine.

Expected Result:

The test lamp illuminated when the engine speed increased past 75 percent of the programmed overspeed setpoint.

Results:

• OK - The test lamp illuminated.

  Repair: The ECM is operating correctly. Perform the following procedure:

  1. Verify the continuity of the ground circuit for the overspeed verify switch.

  2. Isolate the overspeed verify switch from the circuit. Close the switch and measure the continuity across the switch. Open the switch and measure the continuity across the switch.

  3. Verify the continuity of the circuit between the overspeed verify switch and the P1 ECM connector.

  4. Restore the wiring to the original configuration.
  If the overspeed verify that switch is OK and the circuit has continuity from the P1 and the engine ground stud, there is a problem in the wiring between the P1 ECM connector and the air shutoff relay.Repair the circuit connectors or wiring and/or replace the circuit connectors or wiring. Verify that the problem is resolved.

  STOP

• Not OK - The test lamp did not illuminate.

  Repair: Restore the wiring to the original configuration. There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "ECM - Replace".

  STOP

Test Step 6. Test the Diode for the Control Circuit

Illustration 9	g00761537
Diode leads

1. Remove the electrical power from the ECM.

2. Disconnect the air shutoff relays control wires at the relay.

3. Remove the diode from the air shutoff relay.

4. Select the "Diode Check" function on a digital voltmeter.

5. Refer to Illustration 9. Place the red lead of the digital voltmeter on the diode at location (A). Place the black lead of the digital voltmeter on the diode at location (B).

6. Measure the voltage drop across the diode.

Expected Result:

The voltage drop across the diode is less than one volt.

Results:

• OK - The voltage drop across the diode is less than one volt. The voltage drop across the diode is OK. Proceed to Test Step 7.

• Not OK - The voltage drop across the diode is greater than one volt.

  Repair: The diode is damaged. Replace the diode. Verify that the problem is resolved.

  STOP

Test Step 7. Test the Diode for Current Flow

1. Reverse the position of the leads for the digital voltmeter.

2. Measure the voltage drop across the diode.

Expected Result:

For a diode that is operating properly, the digital voltmeter will indicate an OL across the diode.

Results:

• OK - The digital voltmeter indicates an OL across the diode for this measurement. The diode is OK. Proceed to Test Step 8.

• Not OK - The digital voltmeter does not indicate an OL across the diode.

  Repair: The diode is damaged. Replace the diode. Verify that the problem is resolved.

  STOP

Test Step 8. Check the Voltage from the Keyswitch to the Voltage Input of the Air Shutoff Relay

1. Remove the electrical power from the ECM.

Show/hide table



Illustration 10	g02577161
Location of the test lamp

2. Remove the wire at the voltage input of the air shutoff relay.

3. Connect the test lamp between the wire for the voltage input and the terminal for the voltage input at the air shutoff relay.

4. Turn the keyswitch to the ON position.

5. Check the test lamp.

6. Turn the keyswitch to the OFF position.

Expected Result:

The test lamp illuminates.

Results:

• OK - The test lamp illuminated.

  Repair: The relay contacts are not passing the secondary voltage to the circuit for the air shutoff solenoid. Replace the air shutoff relay. Verify that the problem is resolved.

  STOP

• Not OK - The test lamp did not illuminate. Input voltage is not reaching the relay. Proceed to Test Step 9.

Test Step 9. Check the Harness between the Keyswitch and the Air Shutoff Relay

1. Remove the electrical power from the ECM.

2. Turn the keyswitch to the OFF position.

3. Remove the wire from terminal R (keyswitch) of the keyswitch.

4. Turn the keyswitch to the ON position.

5. Measure the voltage between terminal B (+Battery) of the keyswitch and engine ground.

   Refer to Illustration 2 for details.

6. Measure the voltage between terminal R (keyswitch) of the keyswitch and engine ground.

7. Turn the keyswitch to the OFF position.

Expected Result:

Voltage is present on terminal B (+Battery) and terminal R (keyswitch) at the keyswitch.

Results:

• OK - Voltage is present on terminal B and terminal R at the keyswitch.

  Repair: If voltage is present on terminal R, repair the wire between the keyswitch and the air shutoff relay. Verify that the breaker is not tripped. Return all wiring to the original configuration. Verify that the problem is eliminated.

  STOP

• Not OK - Voltage is not present on terminal B at the keyswitch.

  Repair: If voltage is not present on terminal B, repair the wire between the +Battery and the keyswitch. Verify that the breaker is not tripped. Verify that the battery disconnect switch is operating correctly. Check the battery no-load voltage. Return all wiring to the original configuration. Verify that the problem is eliminated.

  STOP

• Not OK - Voltage is not present on terminal R at the keyswitch.

  Repair: If voltage is present on terminal B of the keyswitch but not present on terminal R, replace the keyswitch. Return all wiring to the original configuration. Verify that the problem is eliminated.

  STOP