PULLEY-FAN 1081493 - Caterpillar

System Operation Description: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.
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Schematic for the (S/N: HAZ) ATEX air shutoff system
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Schematic for the standard (S/N: SWE) air shutoff system
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
Remove the electrical power from the ECM.
Verify that the air shutoff mechanisms are set to the OPEN position.
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ECM connectors (typical example) (1) J1/P1 ECM connectors
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Air shutoff mechanism S/N Prefix HAZ (typical example) (2) Air shutoff solenoid
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Air shutoff mechanism S/N Prefix SWE (typical example) (3) Terminals for the air shutoff solenoid
Thoroughly inspect connectors (1) and (2). Also, thoroughly inspect connections (3) at the air shutoff solenoid. Refer to Troubleshooting, "Electrical Connectors - Inspect".
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P1 terminals for the air shutoff system (P1-11) Air shutoff relay (P1-54) Overspeed verify