804034 Mercury SCREW

Recommended 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 "Warranty Report" from the engine ECM before performing any troubleshooting or clearing diagnostic trouble codes.
Codes
Result: A diagnostic trouble code is active or logged.
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.
Drain the fuel system and replace the fuel filters. Refer to the Operation and Maintenance Manual, "Fuel System Primary Filter (Water Separator) Element - Replace" and Operation and Maintenance Manual, "Fuel System Filter - 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 suspect cylinders. Check the following items for damage:
Valve springs
Rocker shaft
Bridges
Pushrods
Camshaft followers
Refer to the Disassembly and Assembly for additional information.
Valve train
Result: Valve train components are damaged.
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.
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 9 was satisfactory, the "Cylinder Cut Out Test" will identify any faulty injectors.
Electronic Unit Injectors
Result: A faulty injector is indicated.
Remove any faulty electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove".
Install new electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector - Install".
Repeat the automatic "Cylinder Cut Out Test". If the fault is still apparent, remove the replacement electronic unit injector and install the original electronic unit injector. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove" and Disassembly and Assembly, "Electronic Unit Injector - Install".
Result: All injectors are OK.
Proceed to Test Step 6.
6. Pistons
A. Inspect the pistons for damage and wear.
Pistons
Result: One or more pistons are worn or damaged.
Replace any worn or damaged parts.
Verify that the repair has eliminated the noise.
Result: All pistons are OK.
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).