56176 Mercruiser SCREW, OIL PUMP TO CYLINDER BLOCK (1 1/4")

Recommended Actions
Table 1
Troubleshooting Test Steps Values Results
1. Check for a Cylinder Misfire
Note: Although the fuel does not ignite, fuel is still supplied to a cold cylinder. The other cylinders must burn more fuel in order to maintain the load. This increases fuel consumption.
Misfire
Result: There is not a cylinder misfire.
Proceed to Test Step 2.
Result: There is a cylinder misfire.
Repair: Troubleshoot the cause of the misfire. Refer to Troubleshooting, "Engine Misfires, Runs Rough, or Is Unstable" for additional information.
If the problem is not resolved, proceed to Test Step 2.
2. Check the Air/Fuel Ratio
Note: A change in the fuel energy content will change the air/fuel ratio.
A. Obtain a fuel analysis.
Note: If the quality of the gas is inconsistent, obtain several analyses over a period of time.
B. Enter the data into Caterpillar Software, LERW4485, "Gas Engine Rating Pro (GERP)".
C. Verify that the fuel supply pressure is adequate and stable.
D. Verify that the exhaust emissions are correct.
Air/Fuel Ratio
Result: The air/fuel ratio is OK.
Proceed to Test Step 3.
Result: The air/fuel ratio is NOT OK.
Repair: Use Cat ET to program the results for the "Fuel Specific Heat Ratio", "Fuel Quality", and "Gas Specific Gravity" parameters. Refer to Systems Operation, "Electronic Control System Parameters" for additional information.
Program the "Fuel Quality" parameter to the average value of the LHV. Adjust the engine operation according to Testing and Adjusting, "BTU and Precombustion Chamber Adjustments".
If the problem is not resolved, proceed to Test Step 3.
3. Check the Needle Valves Adjustments
If the setting for the fuel's LHV is too low, the air/fuel ratio will be too rich.
A. If the needle valves require adjustment, do the following procedure:
- Fully close all of the needle valves.
- Open all of the needle valves 2.5 turns.
- Enter "Engine Prechamber Calibration" mode in Cat ET.
- Record engine average burn time.
- Adjust each needle valve until all cylinders' burn times are within +/- 0.12 milliseconds of the engine average burn time.
- Exit "Engine Prechamber Calibration" mode.
Note: The recommended position of the needle valve is 2.5 turns open.
B. Make sure that the fuel lines for the needle valves are not clogged.
Note: If the needle valve moves freely, the position of the needle valve may change during engine operation due to vibration.
Needle Valves
Result: The needle valves are OK.
Proceed to Test Step 4.
Result: The needle valves are NOT OK.
Repair: Adjust the needle valves to the correct setting. Refer to Testing and Adjusting, "BTU and Precombustion Chamber Adjustments" for additional information.
If the problem is not resolved, proceed to Test Step 4.
Gaseous fuel is present. Personal Injury or Death can result from an open flame or spark igniting the gaseous fuel causing an explosion and/or fire. Always use a gas detector to determine the presence of gaseous fuel when maintaining and servicing. Contact your local gas provider immediately for assistance in the event of a leak.
Table 2
Troubleshooting Test Steps Values Results
4. Inspect the Fuel System for Leaks
Note: Always use a gas detector to determine the presence of gaseous fuel. Contact your local provider of gas immediately for assistance.
Leaks
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 the Valve Lash
Note: The valve lash can affect the performance of the engine.
Valve Lash
Result: The valve lash is OK.
Proceed to Test Step 6.
Result: The valve lash is NOT OK.
Repair: Reset the valve lash. Refer to Testing and Adjusting, "Valve Lash and Valve Bridge Adjustment (Gas Admission Valve Lash)" for additional information.
If the problem is not resolved, proceed to Test Step 6.
6. Inspect the Check Valve
Note: The check valve may be stuck. The check valve must move freely in order to prevent fuel from continuously entering the precombustion chamber.
Check Valve
Result: The check valve is OK.
Proceed to Test Step 7.
Result: The check valve is NOT OK.
Repair: Clean or replace the check valve. Clean with a nonflammable solvent that will not leave residue.
If the problem is not resolved, proceed to Test Step 7.
7. Excessive Deposits in the Combustion Chamber
A. Overfilling of engine oil can lead to deposits. Check the oil level.
B. Use a borescope to inspect the cylinders. Look for the following conditions:
- Deposits on the valve seats
- Deposits on the valve faces
- Deposits on the cylinder walls that are above the upper limit of the piston stroke
- Signs of internal leaks
Note: Signs of internal leaks include excessive consumption of engine oil, blue smoke, and excessive detonation.
Deposits
Result: Deposits or signs of internal leaks are found.
Repair: Investigate the cause of the condition. Repair or replace damaged components.
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).