WRENCH A- 6V7920 - Caterpillar

is NOT an electronic system problem. Refer to the Systems Operation for additional information.The probable root causes are listed below:
Faulty fuel injector(s)
Low fuel pressure
Low engine idle
Faulty engine accessoriesPerform the following checks:
Check for correct installation of the connectors of the Electronic Control Module (ECM) J2/P2 and Fuel Injector connectors J4/P4 through J19/P19. Repair the connector and/or replace the connector. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".
Check for active diagnostic codes. Check for logged diagnostic codes. Perform the Injector Solenoid Test. Verify that the ECM is energizing all the injector solenoids. Refer to the diagnostic functional test Troubleshooting, "Injector Solenoids".
Check fuel lines for the following problems: restrictions, collapse, pinched line and loose fittings. Repair the lines and/or replace the lines. Refer to the Testing and Adjusting, "Fuel System Inspection".
Check the fuel tank for foreign objects which may block the fuel supply. Check for air in the low pressure fuel supply system after you perform the following procedures:
Replacing the fuel filters
Working on the low pressure fuel supply circuit
Replacing fuel injectors
Purge air from the low pressure fuel supply circuit with the hand priming pump and by cranking the engine in 30 second cycles. After you crank the engine, stop for two minutes. This will allow the starting motor to cool. Loosen the fuel return vent plug. The plug is located on the rear upper left side of the engine block. Hand prime the engine again if air in fuel continues. A sight glass in the low pressure supply line is helpful in diagnosing air in the fuel.
Check fuel quality. In temperatures below 0 °C (32 °F), check for solidified fuel (wax). Refer to Special Publication, SEBD0717, "Diesel Fuels And Your Engine". Check the fuel pressure with engine cranking. Check the fuel pressure at the filter. Refer to Testing and Adjusting, "Fuel Pressure". If pressure is low, check for plugged fuel filters. If the fuel pressure is still low check the following items: fuel transfer pump, fuel transfer pump coupling and fuel pressure regulating valve. Check for a combustion problem.
Check for restrictions in the air inlet system. Refer to Testing and Adjusting, "Restrictions of Air Inlet and Exhaust".
Check the setting for the low engine idle.
Check all flywheel and damper driven accessory equipment for proper operation. Ensure that the accessory equipment is not lugging down the engine.