3512C Engines for 785C Off-Highway Trucks with Dynamic Gas Blending Caterpillar

Power Is Intermittently Low or Power Cutout Is Intermittent

Usage:

3512 8BR

Use this procedure to troubleshoot an engine that has intermittent low power or power cutout.

Note: Use this procedure only if the engine does not shutdown completely.

Probable Causes

Connectors and wiring
Throttle signal
Fuel injectors
Fuel system
Inlet air restriction

Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high engine speed, full load, and engine operating temperature. Troubleshooting the symptoms under other conditions can give misleading results.

Show/hide table

Table 1
Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Check for the correct installation of the ECM J1/P1 and the J2/P2 connectors. Refer to Troubleshooting, "Electrical Power Supply - Test" for additional information. C. Check for correct installation of the following connectors: - Connectors for the wiring harness under the valve cover - Connectors for the engine speed/timing sensors D. Check the power and ground connections to the ECM. Refer to Troubleshooting, "Electrical Power Supply - Test" for additional information.	Connectors and Wiring	Result: The connectors and wiring appear to be OK. Proceed to Test Step 2. Result: There is a problem with the connectors and/or wiring. Repair: Repair or replace the connectors or wiring. Ensure that all the seals are properly in place and ensure that the connectors are coupled. If the problem is not resolved, proceed to Test Step 2.
2. Check for an Intermittent Throttle Signal A. Connect Cat^® Electronic Technician (ET) to the service tool connector. B. Use Cat ET to monitor the following: - "Throttle Position" C. Verify that the status for "Throttle Position" is stable and that the engine is able to reach high idle speed.	Throttle Signal	Result: The status for "Throttle Position" is stable. Proceed to Test Step 3. Result: The status for "Throttle Position" is not stable. Repair: Repair or replace damaged components. Refer to Troubleshooting, "Speed Control - Test" for additional information. If the problem is not resolved, proceed to Test Step 3.
3. Test the Fuel Injectors A. Connect Cat ET. B. Use Cat ET to perform the following fuel injector tests: - "Injector Solenoid Test" - "Cylinder Cutout Test" Refer to Troubleshooting, "Cat ET Service Features" for additional information.	Fuel Injectors	Result: The tests were successful. Proceed to Test Step 4. Result: The tests were not successful. Repair: Diagnose the problem. Repair or replace damaged components. If the problem is not resolved, proceed to Test Step 4.
4. Inspect the Fuel System Refer to Testing and Adjusting, "Fuel System Inspection" for additional information. A. Visually check the fuel level in the fuel tank. Do not rely on the fuel gauge only. B. Ensure that the vent in the fuel cap is not filled with debris. C. Ensure that the fuel supply valve (if equipped) is in the full OPEN position. Note: Cold weather adversely affects the characteristics of the fuel. Refer to the engines Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold-weather operation. D. Check fuel quality. Refer to Testing and Adjusting, "Fuel Quality - Test" for additional information. Check the fuel tank for debris or foreign objects which may block the fuel supply. E. Obtain a diesel fuel and gas analysis. The grade of the fuel affects the rate of fuel consumption. Refer to the engines Operation and Maintenance Manual for additional information. F. Check for fuel leaks.	Fuel System	Result: The fuel system is OK. Proceed to Test Step 5. Result: The fuel system is NOT OK. Repair: Repair or replace damaged fuel system components. If the problem is not resolved, proceed to Test Step 5.
5. Check for a Restriction in the Inlet Air System A. Check the air filter restriction indicator, if equipped. Refer to the Operation and Maintenance Manual for additional information. B. Measure the inlet air restriction for each turbocharger. Refer to Troubleshooting, "Inlet Air Is Restricted" for additional information.	Restriction	Result: The inlet air restriction is NOT OK. An imbalance in the system is discovered. Repair: Repair or replace damaged inlet air system components. Equalize the inlet air restriction for each of the turbochargers. Verify that the repair eliminated the problem.

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).