GEAR-TRANSFER 7T3742 - Caterpillar

Probable Causes
Misfire
Incorrect air/fuel ratio
Fuel system leaks
Improper gas admission valve lash
A check valve is stuck in the open position.
Incorrect adjustments of the needle valves
Deposits in the combustion chamberRecommended Actions
Misfire
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. Refer to Troubleshooting, "Engine Misfires, Runs Rough or Is Unstable".Air/Fuel Ratio
If the setting for the fuel's LHV is too low, the air/fuel ratio will be too rich. Obtain a gas analysis. Enter the data into Caterpillar Software, LEKQ6378, "Methane Number Program". Use Caterpillar Electronic Technician (ET) to program the results for the "Fuel Quality" and "Gas Specific Gravity" parameters. For more information, refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters".If the quality of the gas is inconsistent, obtain several analyses over a period of time. Program the "Fuel Quality" parameter to the average value of the LHV.Adjust the engine operation according to Systems Operation/Testing and Adjusting, "BTU and Precombustion Chamber Adjustments".Fuel System Leaks
Always use a gas detector to determine the presence of gaseous fuel. If a leak is found, contact your local provider of gas immediately for assistance.Gas Admission Valve Lash
Adjust the gas admission valve lash according to Systems Operation/Testing and Adjusting, "Engine Timing Procedures".Check Valve
The check valve may be stuck. The check valve must move freely in order to prevent fuel from continuously entering the precombustion chamber. Inspect the check valve. Clean the check valve with a nonflammable solvent that will not leave residue. Replace the check valve, if necessary.Needle Valve
Check the needle valves for the precombustion chambers. If the needle valves are open too far, the air/fuel mixture will be too rich. If the adjustment of the needle valves is suspect, fully close all of the needle valves. Open the needle valves for four full turns. Adjust the needle valves according to Systems Operation/Testing and Adjusting, "BTU and Precombustion Chamber Adjustments".Note: The recommended minimum position of the needle valve should not be less than two turns open.If adjustment of a needle valve does not affect operation, the needle valve may be faulty. Replace the needle valve.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. If this condition exists, replace the needle valve. If the needle valve replacement and subsequent adjustment does not change the burn time, inspect the precombustion chamber tip for nozzle erosion.Deposits
Deposits that are burned in the combustion chamber will increase the exhaust emissions. An internal leak of engine oil or coolant can be burned with the air and fuel.Inspect the combustion chambers according to Operation and Maintenance Manual, "Cylinders - Inspect". Inspect the spark plug and the precombustion chamber for evidence of coolant and residue of liquid crystalline material. If the gasket and/or the seals have leaked, clean the sealing surfaces and install a new gasket and seals. Also