G3516 TA Engine Caterpillar

Engine Overspeeds

Usage:

Use this procedure to troubleshoot an engine overspeed or use this procedure if any of the following event codes are active or logged.

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Table 1
J1939 Code and Description	Comments
190–0 Engine Speed : High - most severe (3)	The engine rpm has exceeded the trip point that is programmed into the Electronic Control Module (ECM). The shutdown output is activated. The gas shutoff valve is de-energized. the ignition is shut off. The code is logged. The engine is shutdown.

Note: Refer to Troubleshooting, "Engine Monitoring System" for information on trip points and delay times.

The ignition is immediately terminated when the emergency stop button is pressed. Unburned gas remains in the air inlet and exhaust system.

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Unburned gas in the air inlet and exhaust system may ignite when the engine is started. Personal injury and/or property damage may result.

Before starting an engine that may contain unburned gas, purge the unburned gas from the air inlet and exhaust system. Refer to the topic on purging unburned gas in the "Starting the Engine" section.

Probable Causes

Low trip point for engine overspeed
There is a problem with the input for the keyswitch.
Energy of the driven equipment
Binding of the throttle actuator
Slow governor response

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat^® Electronic Technician (ET) to the service tool connector. B. Look for active codes that are associated with the system for the event code.	Codes	Result: An associated code is active. Repair: Troubleshoot any associated codes before continuing with this test. Result: An associated code is NOT present. Proceed to Test Step 2.
2. Check the Trip Point NOTE: Do not program the trip point for engine overspeed higher than the maximum ratings of the driven equipment. A. Verify that the trip point for the engine overspeed is properly programmed. Typically, this parameter is set at 118 percent of rated speed. B. This parameter requires a factory password to change the trip point. Change the trip point to an acceptable speed, if necessary.	Trip Point	Result: The programmed trip point for overspeed is correct. Proceed to Test Step 3. Result: The programmed trip point for overspeed is too high. Repair: Decrease the programmed trip point for overspeed.
3. Verify that the Voltage on the Keyswitch Circuit is Stable An engine shutdown or an engine overspeed may occur due to a problem with the input for the keyswitch for one of the following: - Actuator for the throttle - Actuator for the turbocharger compressor bypass valve - Actuator for the fuel metering valve - ECM A. Verify that the input for the keyswitch to the actuators is not intermittent.	Keyswitch Input	Result: The input for the keyswitch to the actuators is NOT intermittent. Proceed to Test Step 4. Result: The input for the keyswitch to the actuators is intermittent. Repair: Remedy the cause for the intermittent keyswitch input.
4. Check the Driven Equipment A. Determine if the driven equipment has additional inputs of energy that could drive the engine beyond the trip point.	Energy	Result: No additional energy input was identified. Proceed to Test Step 5. Result:Additional energy input was identified. Repair: Make corrections to the installation to prevent the overspeed from recurring.
5. Check for Binding of the Throttle Actuator A. Set the engine control to the OFF/RESET mode. B. Remove the electrical power from the engine. C. Move the throttle plate while you feel the motion. If the motion is sticky and/or rough, investigate the cause of the binding. Make the necessary repairs.	Binding	Result: The actuator is OK. Proceed to Test Step 6. Result: The actuator is NOT OK. Repair: Remedy the cause of the binding.
6. Check for Slow Governor Response A. Observe the "Speed Governor Adjustment" screen on the Caterpillar Electronic Technician (ET). Look for the engine response to the worst cases for step-loading and unloading. Refer to System Operation Test and Adjust, "Engine Governing - Adjust"	Governor Response	Result: Adjustment is required for the electronic governor. Repair: Adjust the electronic governor.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).