U-BOLT 3N9606 - Caterpillar

System Operation Description:The ECM has the ability to stop the engine by cutting off the air supply in an emergency situation. The ECM activates a relay which activates the air shutoff solenoid.There are two conditions which cause the engine control to activate the air shutoff relay. The first condition occurs when the operator initiates a shutdown. When the shutdown is recognized, fuel is shut off and the air shutoff relay is activated. The ECM will hold the relay active for 1.5 seconds. The second condition is for an engine overspeed. Engine overspeed can be a real overspeed condition. Overspeed can be obtained by using the overspeed verify switch.The air shutoff relay can also be activated without the aid of the ECM. When the emergency stop is used, a relay is activated for 2.5 seconds.Regardless of the reason for activation, the ECS must be turned to the OFF/RESET position for three seconds in order to reset the engine controls.
Illustration 1 g00598786
SchematicTest Step 1. Check for Connector Damage
Verify that the circuit breakers are not tripped.
Turn the circuit breaker for the battery to the OFF position.
Turn the ECS to the OFF/RESET position.
Check connectors and wiring for the following problems: damage, corrosion, abrasion and incorrect attachment.Expected Result:The connectors and wiring should be free of the following problems: damage, corrosion, abrasion and incorrect attachment.Results:
OK - Proceed to test step 2.
Not OK - Repair: Repair the connectors and/or wiring or replace the connectors and/or wiring. Stop.Test Step 2. Check the Air Shutoff System.
Turn the circuit breaker for the battery to the ON position.
Turn the ECS to the STOP position.
Connect the ET.
Access the override on the ET. Activate the override for the air shutoff.
Disable the override for the air shutoff.Expected Result:The air shutoff relay should activate. The air shutoff relay should deactivate after two seconds. While the relay is active, the air shutoff solenoid should also be active.Results:
OK - The system is operating properly at this time. Stop.
Relays ON - The relay activated but the air shutoff solenoid did not activate. Proceed to test step 3.
Not OK - Both the relay and the solenoid failed to activate. Proceed to test step 4.Test Step 3. Check the Relay.
Turn the circuit breaker for the battery to the OFF position.
Turn the ECS to the OFF/RESET position.
Disconnect the wire from terminal 85 and from terminal 86 of the air shutoff relay.
Obtain two suitable pieces of 18 AWG wire. Connect one end of the first wire to -Battery. Connect the other end to terminal 85 of the air shutoff relay.
Connect one end of the second wire to +Battery. Connect the other end to terminal 86 of the air shutoff relay for two seconds.Expected Result:The air shutoff solenoid should activate when the wire is connected to +Battery.Results:
OK - The relay is operating correctly. The problem is most likely in the wiring.Repair: Repair the connectors and/or wiring or replace the connectors and/or wiring. Stop.
Not OK - The air shutoff relay did not activate. The problem appears to be in the air shutoff relay.Repair: