WASHER (spring) 6N2956 - Caterpillar

Probable Causes
Diagnostic codes
Fuel quality
Injectors
Valve train components
Low compression (cylinder pressure)
Pistons and connecting rodsRecommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.
Table 1
Troubleshooting Test Steps Values Results
1. Diagnostic Codes
A. Establish communication between the electronic service tool and the Electronic Control Module (ECM).
B. Download the Product Status Report before performing any troubleshooting or clearing any diagnostic codes.
Note: The downloaded information will be required by the Dealer Solutions Network (DSN) if troubleshooting assistance is needed.
C. Use the electronic service tool to check for active or logged codes.
Codes
Result: A diagnostic trouble code is active or logged.
Repair: Troubleshoot the active or logged codes.
Result: A diagnostic trouble code is not active or logged.
Proceed to Test Step 2.
2. Fuel Quality
A. Check the fuel quality. Refer to Systems Operation, Testing, and Adjusting, "Fuel Quality - Test".
B. Refer to Operation and Maintenance Manual for information on the proper characteristics of the fuel for the engine.
Fuel
Result: The fuel quality is not OK.
Repair: Drain the fuel system and replace the fuel filters. Refer to the Operation and Maintenance Manual, "Fuel System (Water Separator) Element - Replace" and Operation and Maintenance Manual, "Fuel System Filter (in-Line) - Replace".
Fill the fuel system with fuel that meets the standard in the Operation and Maintenance Manual, "Fluid Recommendations".
Prime the fuel system. Refer to the Operation and Maintenance Manual, "Fuel System - Prime".
Verify that the procedure has eliminated the noise.
Result: The fuel quality is OK.
Proceed to Test Step 3.
3. 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 engine. Check the following items for damage:
Valve springs
Rocker shaft
Bridges
Pushrods
Valve lifters
Refer to the Disassembly and Assembly for additional information.
Valve train
Result: Valve train components are damaged.
Repair: Make the necessary repairs, Verify that the repair has eliminated the noise.
Result: The valve train components are not damaged.
Proceed to Test Step 4.
4. Low Compression (Cylinder Pressure)
A. Perform a compression test. Refer to Systems Operation, Testing, and Adjusting, "Compression - Test ".
Cylinder compression
Result: The results of the compression test are outside the specifications.
Repair: Investigate the cause and rectify any faults.
Note: Possible causes of low compression are shown in the following list:
Loose glow plugs
Faulty piston
Faulty piston rings
Worn cylinder bores
Worn valves
Faulty cylinder head gasket
Damaged cylinder head
Result: The results of the compression test are OK.
Proceed to Test Step 5.
5. Electronic Unit Injectors
A. Use the electronic service tool to perform the automatic "Cylinder Cut Out Test".
Note: If the compression test that was performed in Test Step 4 was satisfactory, the "Cylinder Cut Out Test" will identify any faulty injectors.
Electronic Unit Injectors
Result: A faulty injector is indicated.
Repair: Remove any faulty electronic unit injectors. Refer to