C7 and C9 Industrial Engines Troubleshooting – Air Shutoff – Test

A. Remove electrical power from the ECM.

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

C. Thoroughly inspect the connectors. Also, inspect the connections at the air shutoff solenoid. Refer to Troubleshooting, “Electrical Connectors – Inspect” for more information.

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

E. 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.

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

Result: The electrical connectors are NOT OK.

Repair: Repair or replace the damaged parts and return to service.

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

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

D. Start the engine.

E. Activate the overspeed verify switch.

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

G. Stop the engine.

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

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

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

D. Start the engine.

E. Activate the overspeed verify switch.

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

G. Stop the engine.

STOP

Results: 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.

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

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

D. Start the engine.

E. Activate the overspeed verify switch.

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

G. Stop the engine.

Repair: 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.

B. Disconnect the P1 ECM connector.

C. 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.

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

E. 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.

F. 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.

G. Connect the J1/P1 ECM connectors.

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

I. 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.

J. Start the engine.

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

L. Stop the engine.

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
Results: 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, “Replacing the ECM”.

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B. Remove the diode from the air shutoff relay.

C. Select the “Diode Check” function on a digital voltmeter.

D. 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).

E. Measure the voltage drop across the diode.

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

STOP

B. Measure the voltage drop across the diode.

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

STOP