COUPLING AS 7T3457 - Caterpillar

Probable Causes
Low quality fuel
Electrical connectors
Injector
Not enough lubrication
Too much valve lash
Damage to valve train components
Failure of connecting rod bearingRecommended Actions
Low Quality Fuel
Refer to Operation and Maintenance Manual for information on the proper characteristics of the fuel. Obtain a fuel analysis.Electrical Connectors
Check for the correct installation of the connector(s) for the Electronic Control Module (ECM) J1/P1 and/or J2/P2. Check for correct installation of the applicable fuel injector connectors. Repair the connector and/or replace the connector. Refer toTroubleshooting, "Electrical Connectors - Inspect".Injector
Use Caterpillar Electronic Technician (ET) to determine if any diagnostic codes for the injector solenoids are present. Perform the "Injector Solenoid Test". Observe that the injector solenoids are being energized on Cat ET. Perform the "Cylinder Cutout Test". Locate the misfiring cylinder. Refer to Troubleshooting, "Injector Solenoid - Test".Not Enough Lubrication
Check the lubrication in the valve compartment. Check for sufficient lubrication between the injector tappet and the rocker arm buttons. Check for blocked oil passages. Oil passages must be clean. Ensure that the oil passages that send oil to the cylinder heads are clean.Valve Lash
Check the valve lash. Refer to Troubleshooting, "Valve Lash Is Excessive".Damage to Valve Train Components
Remove the valve cover from the suspect cylinder(s). Check the following items for damage: camshaft, valve rotocoil, valve springs, lifters, pushrods and bridges. Check for valves that do not move freely. Remove the cylinder head. Inspect the valves. Replace any damaged parts.Failure of Connecting Rod Bearing
Inspect the connecting rod bearings and the bearing surfaces (journals) on the crankshaft. Check the piston pin for excessive wear. Replace any damaged parts.