Probable Causes
- Engine derate or active codes
- Cold mode
- Electrical connectors
- Low compression (cylinder pressure)
- Individual malfunctioning cylinder
- Valve lash
- Faulty fuel injector nozzle
- Throttle signal
- Fuel supply
- Air inlet and exhaust system
Engine Derate or Active Codes
Some engine monitoring parameters that are capable of triggering an engine derate do not produce an event code. Connect Caterpillar Electronic Technician (ET) in order to check for a derate of the engine.
Certain diagnostic codes and may cause poor performance. Use Cat ET to check for active codes and for logged codes. Troubleshoot any codes that are present before you continue with this procedure.
Note: Although a sensor's signal may be in the operational range of the sensor, the signal may not represent the actual reading. Use Cat ET to check that the pressures and the temperatures are fluctuating. Also check that the values are reasonable for the conditions that are present.
Cold Mode
The Electronic Control Module (ECM) limits engine power during cold mode operation. The ECM may cut out certain engine cylinders. This will increase startability and this will reduce warm up time. Cold mode is activated whenever the engine coolant temperature falls below a predetermined value. Cold mode remains active until the engine has warmed or a time limit is exceeded.
Electrical Connectors
Check for correct installation of the J14/P14 ECM connector. Refer to Troubleshooting, "Electrical Connectors - Inspect".
Low Compression (Cylinder Pressure)
- Perform a compression test. Refer to Systems Operation, Testing and Adjusting, "Compression - Test ".
- If low compression is noted on any cylinders, investigate the cause and rectify the cause.
Possible causes of low compression are shown in the following list:
- Loose glow plugs (if equipped)
- Faulty piston
- Faulty piston rings
- Worn cylinder bores
- Worn valves
- Faulty cylinder head gasket
- Damaged cylinder head
- Loose glow plugs (if equipped)
- Perform all necessary repairs.
- Ensure that the repairs have eliminated the faults.
Individual Malfunctioning Cylinders
- With the engine speed at a fast idle, loosen the high pressure fuel line to the fuel injector of number one cylinder. Note if there is any reduction in engine speed. Tighten the high pressure fuel line to the fuel injector.
- Individually repeat this procedure for each fuel injector. If there is no reduction in the engine speed, investigate the cause of the malfunction.
Valve Lash
Check valve lash on misfiring cylinder. Refer to Testing and Adjusting, "Engine Valve Lash - Inspect/Adjust" for the correct procedure.
Faulty Fuel Injector Nozzle
Remove the suspect fuel injection nozzle. Test the nozzle by using the 5P-4150 Nozzle Testing Group. Refer to Systems Operation, Testing and Adjusting, "Fuel System" for the proper testing procedure. Replace the fuel injector nozzles, as needed.
Throttle Signal
Monitor the status for "Throttle Position" on Cat ET. Verify that the status for "Throttle Position" is stable and that the engine is able to reach high idle speed. If a problem is suspected with the throttle, refer to the appropriate troubleshooting procedure for troubleshooting the throttle signal.
Fuel Supply
- Visually check the fuel level in the fuel tank. Do not rely on the fuel gauge only. If necessary, add fuel to the fuel tank. If the engine has been run out of fuel, it will be necessary to purge the air from the fuel system. Refer to Operation and Maintenance Manual for the correct procedure.
- Check the fuel lines for the following problems: restrictions, collapsed lines and pinched lines. If problems are found with the fuel lines, repair the lines and/or replace the lines.
- Check the fuel tank for debris or foreign objects which may block the fuel supply.
- Prime the fuel system if any of the following procedures have been performed:
- Replacement of the fuel filters
- Service on the low pressure fuel supply circuit
Note: Check the fuel system for air. Refer to Systems Operation/Testing and Adjusting for information that is related to checking the fuel system for air.
- Replacement of the fuel filters
| NOTICE |
|---|
Do not crank the engine continuously for more than 30 seconds. Allow the starting motor to cool for two minutes before cranking the engine again. |
- Check fuel quality. Cold weather adversely affects the characteristics of the fuel. Refer to the engine's Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold weather operation.
- Check the filtered fuel pressure while the engine is being cranked. Refer to Systems Operation/Testing and Adjusting for the test procedure and for the correct pressure values.
If the fuel pressure is low, replace the fuel filters. Clean the primary filter/water separator of debris. Refer to the Operation and Maintenance Manual for details.
If the fuel pressure is still low, check the operation of the fuel pressure regulating valve. Also, check for the proper operation of the fuel transfer pump. Refer to Systems Operation/Testing and Adjusting for test information.
Air Inlet and Exhaust System
- Check for an air filter restriction. Clean plugged air filters or replace plugged air filters. Refer to the Operation and Maintenance Manual.
- Check the air inlet and exhaust system for restrictions and/or leaks. Refer to Systems Operation/Testing and Adjusting for information on inspecting the air inlet and exhaust system.