PLATE-TREAD 5223437 - Caterpillar

Hydraulically Actuated Air Shutoff Valves
Note: After checking the fluids in the engine, ensure that both air shutoff valves are latched in the open position. Start the engine and operate the engine at 1500 RPM. This will allow the fluids to warm up before proceeding with the test for the air shutoff valves.
Manually trip one of the air shutoff valves. This should cause an emergency stop condition and the remaining air shutoff valve should close. If the engine experienced an emergency stop condition but the remaining valve did not close, purge the air from the line that goes to the hydraulic cylinder for the air shutoff valve. If the engine did not have an emergency stop condition the switches are not correctly wired into the emergency stop circuit. Note: Both switches should be in a closed state and both switches should show continuity when the air shutoffs are latched in the open position. After the issue with the wiring has been resolved repeat step 1.
Close one air shutoff valve and attempt to start the engine. If the engine cranks but the engine will not start, the switches are functioning correctly. Caterpillar Electronic Technician (ET) will also show an active emergency stop condition. Proceed to step 3. If the engine starts with one of the air shutoffs closed, check the switch on the valve that is closed. The switch should not have continuity. If the switch has continuity, remove the switch and inspect the switch. If the switch does not show continuity, troubleshoot the switch wiring further. Repair the necessary components or replace the necessary components. Retest the system, as required.
With both air shutoff valves in the open position, activate the emergency stop. Both air shutoff valves should close. If both valves close, testing is complete. If only one air shutoff closes, purge air from the line at the cylinder that failed to close and repeat this step. Note: Testing is only complete when the engine successfully passes all of the steps. Reset both air shutoff valves to the open position and clean up any spills that may have occurred.Note: The limit switch assemblies are items that wear and the limit switch assemblies may need to be replaced during normal maintenance intervals.