3512B, 3512C, and 3516B Petroleum Engines and Petroleum Generator Set Engines with Dynamic Gas Blending Caterpillar

Engine Has Mechanical Noise (Knock)

Usage:

Probable Causes

Active codes and logged codes
Electrical connections
Fuel injection
Fuel quality
Proper lubrication
Isolate the source of the noise.
Valve train components
Gear train and lower end components
Crankshaft

Recommended Actions

Note: The procedures have been listed in order of probability. Complete the procedures in the order of the listed test steps.

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Table 1
Troubleshooting Test Steps	Values	Results
1. Check for Active Codes and Logged Codes A. Establish communication between Caterpillar Electronic Technician (ET) and the Electronic Control Module (ECM). B. Monitor the diagnostic codes on Cat ET. Check for any active or logged codes. Note: Wait at least 30 seconds in order for diagnostic codes to become active.	Codes	Result: A code is active or logged. Repair: Troubleshoot any codes before continuing with this procedure. Verify that the repair eliminated the problem. Result: A code is not active or logged. Proceed to Test Step 2.
2. Inspect the Electrical Connections A. Check for the correct installation of the ECM J1/P1 and the J2/P2 connectors. Check for correct installation of the fuel injector connectors.	Connectors	Result: There are suspect connectors. Repair: Repair connectors that are suspect or replace connectors that are suspect. Perform the "Wiggle Test" on Cat ET. Verify that the repair eliminated the problem. Result: There are no suspect connectors. Proceed to Test Step 3.
3. Test the Fuel Injectors A. Perform the "Injector Solenoid Test" on Cat ET in order to determine if all of the injector solenoids are being energized by the ECM. B. Access the "Cylinder Cutout Test" in the "Diagnostic Tests" under the "Diagnostics" menu. C. Perform the "Automatic Cylinder Cutout Test" on Cat ET.	Fuel Injector	Result: The test was successful. Proceed to Test Step 4. Result: The test was not successful. Repair: Diagnose the problem and then repair the problem. Reset all active codes and clear all logged codes. Verify that the repair eliminated the problem.
4. Check the Fuel Quality A. Refer to Operation and Maintenance Manual for information on the proper characteristics of the fuel for the engine. If necessary, obtain a fuel analysis in order to confirm that the correct fuel is being used for the engine. Refer to Systems Operation/Testing and Adjusting, "Fuel System Quality Test" for the proper procedure.	Fuel	Result: The fuel quality is OK. Proceed to Test Step 5. Result: The fuel quality is NOT OK. Repair: Replace the fuel. Verify that the repair eliminated the problem.
5. Check for Proper Lubrication A. Check for proper lubrication of the valve components. Check for sufficient lubrication between the injector tappets and the rocker arms. B. Check for blocked oil passages. Oil passages must be clean. Clean any oil passages that are questionable. Refer to the Disassembly and Assembly for additional information. C. Inspect the engine oil filters for ferrous material. D. Obtain an S-O-S oil analysis. The analysis will contribute to a better understanding of oil contamination and the origin of the contamination.	Lubrication	Result: The oil passages are not blocked and the engine has proper lubrication. Proceed to Test Step 6. Result: The oil passages are blocked or the engine does not have proper lubrication. Repair: Make the necessary repairs. Verify that the repair eliminated the problem.
6. Isolate the Source of the Noise A. If the source of the noise is the engine accessory, remove the suspect engine accessory. Inspect the suspect engine accessory.	Engine Accessory	Result: An engine accessory is the source of the noise. Repair: Repair the engine accessory and/or replace the engine accessory, if necessary. Verify that the repair eliminated the problem. Result: An engine accessory is not the source of the noise. Proceed to Test Step 7.
7. Inspect the Valve Train Components A. Check the valve lash. Refer to Troubleshooting, "Valve Lash Is Excessive". B. Check for damage to valve train components. Remove the valve cover from the suspect cylinders. Check the following items for damage: - Camshaft - Valve rotocoil - Valve springs - Camshaft followers - Rocker shaft - Bridges - Pushrods - Injectors Refer to the Disassembly and Assembly for additional information. C. Check for valves that do not move freely. Remove the cylinder head and inspect the valves. Refer to the Disassembly and Assembly for additional information.	Valve Train	Result: The valve train components are not damaged. Proceed to Test Step 8. Result: The valve train components are damaged. Repair: Make the necessary repairs. Verify that the repair eliminated the problem.
8. Inspect the Gear Train and Components of the Lower End	Gear Train	Result: The gear train or lower end components are damaged. Repair: Replace any damaged parts. Verify that the repair eliminated the problem. Result: The gear train or lower end components are not damaged. Proceed to Test Step 9.
9. Inspect the Crankshaft and the Related Components A. Look for worn thrust plates and wear on the crankshaft. B. Inspect the connecting rod bearings and the bearing surfaces on the crankshaft. Make sure that the bearings are in the correct position. C. Check the counterweight bolts.	Crankshaft	Result: The crankshaft or the related components are damaged or worn. Repair: Repair or replace any damaged parts. Verify that the repair eliminated the problem. 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).