PUMP GP-UNIT INJECTOR HYD 4768768 - Caterpillar

Probable Causes
Diagnostic codes
Fuel quality
Unit injectors
Valve lash
Cylinder head and related componentsRecommended Actions
Table 1
Troubleshooting Test Step Values Results
1. Check for Active Codes and Logged Codes
A. Establish communication between Cat Electronic Technician (ET) and the Electronic Control Module (ECM).
B. Certain event codes may derate engine power. Monitor the diagnostic codes on Cat ET. Check for active diagnostic codes and logged codes (intermittent problems).
Note: Wait at least 30 seconds in order for diagnostic codes to become active.
Codes
Result: A code is active or logged.
Repair: Troubleshoot any codes before continuing with this procedure.
Verify that the repair eliminated the problem.
Result: A code is not active or logged.
Proceed to Test Step 2.
2. Fuel Supply
Refer to System Operation/Testing and Adjusting "Fuel System - Inspect" for additional information.
A. Visually check the fuel level in the fuel tank. Do not rely on the fuel gauge only.
B. Ensure that the vent in the fuel cap is not filled with debris.
C. Ensure that the fuel supply valve (if equipped) is in the full OPEN position.
Cold weather adversely affects the characteristics of the fuel. Refer to the engines Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold-weather operation.
D. Check the fuel quality. Refer to Systems Operation/Testing and Adjusting, "Fuel Quality - Test" for the proper procedure. Check the fuel tank for debris or foreign objects which may block the fuel supply.
E. Check the filtered fuel pressure while the engine is being cranked. Refer to Troubleshooting, "Fuel Pressure Is Low" for the proper testing procedure.
Fuel System
Result: The fuel system is NOT OK.
Proceed to Test Step 3.
Repair: Repair or replace damaged fuel system components.
Verify that the repair eliminated the problem.
3. Unit Injectors
A. Perform the "Injector Solenoid Test" on Cat ET in order to determine if all of the injector solenoids are being energized by the ECM.
B. Perform the "Cylinder Cutout Test" in order to identify any injectors that might be misfiring.
Note: Refer to the procedure in Special Instruction, "Procedure for Troubleshooting and Cleaning the Oil Rail System for the Hydraulic Electronic Unit Injector".
Fuel Injectors
Result: The tests were successful.
Proceed Test Step 4.
Result: The tests were NOT successful.
Repair: Remove the suspect injector, and install a new electronic unit injector. Refer to Disassembly and Assembly.
Ensure that the repairs have determined the problem. Refer to Troubleshooting"Injector Solenoid - Test" and Troubleshooting, "Injection Actuation Pressure - Test".
4. Check the Valve Lash
A. Inspect the valve train for sufficient lubrication.
B. Check for damage to valve train components which may cause excessive valve lash.
Valve Lash
Result: The valve lash and components are OK.
Proceed to Test Step 5.
Result: The valve lash and components are NOT OK.
Repair: Reset the valve lash. Refer to Systems Operation/ Testing and Adjusting, "Valve Lash - Adjust"for additional information.
5. Cylinder and Related Components
A. Check for signs of damage and/or wear to the valves, cylinder head gaskets, and other head components.
B. Inspect the condition of the camshaft.
Engine Components
Result: The engine components and/or camshaft has damage and/or wear.
Repair: Repair or replace damaged components.