0324677 JOHNSON O-RING, Valve core, upper

Probable Causes
Derate or high altitude operation
Active codes and logged codes
Electrical connectors
Throttle signal
Fuel system
Fuel supply pressure
Air inlet and exhaust systemRecommended Actions
Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high engine speed, full load, and engine operating temperature. Troubleshooting the symptoms under other conditions can give misleading results.Note: The procedures have been listed in order of probability. Complete the procedures in the order of the listed test steps.
Table 1
Troubleshooting Test Steps    Values    Results    
1. Check Derate or High Altitude Operation
A. Connect Caterpillar Electronic Technician (ET) and check for logged events that derate engine power. An engine derate indicator will appear on Cat ET if an active engine derate is occurring.
B. Determine the operating conditions of the engine. Interview the operator, when possible. Determine if an excessive load was placed on the engine during the low-power complaint. Determine if the engine is operating at a high altitude.
   
Derate or Altitude
   
Result: The engine is not operating at a high altitude.
Proceed to the next step.
Result: The engine is operating at a high altitude.
Repair: Make sure that the settings for the engine are correct for the altitude.
If the problem is not resolved, proceed to the next step.
   
2. Active Codes and Logged Codes
A. Establish communication between Caterpillar 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 3.
   
3. Electrical Connections
A. Verify that the following connectors are installed correctly:
- Electrical connectors for the ECM
- Connectors for the wiring harness under the valve cover
- Connectors for the engine speed/timing sensors
   
Electrical connectors    
Result: The connectors are installed correctly.
Proceed to Test Step 4.
Result: The connectors are not installed correctly.
Repair: Install the connectors correctly. Refer toTroubleshooting, "Electrical Connectors - Inspect" for the proper troubleshooting procedure.
Verify that the repair eliminated the problem.
   
4. Intermittent Throttle Signal
A. Monitor the status for "Throttle Position" on Cat ET.
B. Verify that the status for "Throttle Position" is stable and that the engine is able to reach high idle speed.
   
Throttle signal    
Result: The status for "Throttle Position" is stable.
Proceed to Test Step 5.
Result: The status for "Throttle Position" is not stable.
Repair: Make the necessary repairs. Refer to Troubleshooting, "Speed Control - Test".
Verify that the repair eliminated the problem.
   
5. Fuel System
A. Ensure that the fuel system is operating properly.
B. Start the engine.
C. Access the Cylinder Cutout Test in the Diagnostic Tests under the "Diagnostics" menu.
D. Select the "Automatic Cylinder Cutout Test" on Cat ET.
   
Cylinder cutout test    
Result: The "Cylinder Cutout Test" was successful.
Proceed to Test Step 6.
Result: The "Cylinder Cutout Test" was not successful.
Repair: Repair the cylinders that failed the "Cylinder Cutout Test". Reset all active codes and clear all logged codes.
Verify that the repair eliminated the problem.
   
6. Fuel Supply Pressure
A. Check the fuel pressure. Ensure that the fuel is stable. Refer to Systems Operation/Testing and Adjusting for the procedure to check the fuel pressure manually.
B. Visually check the fuel level. Do not rely on the fuel gauge only. If necessary, add fuel. If the engine has been run out of fuel, purge the air from the fuel system.
C. Ensure that the fuel supply valve (if equipped) is in the full OPEN position.
D. Check the fuel lines for the following problems:
- Restrictions
- Collapsed lines
- Pinched lines
- Loose connections
E. 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
- Replacement of unit injectors
F. Check the fuel tank for foreign objects which may block the fuel supply.
G. Check the fuel filters.
H. Check the fuel quality. Make sure that the fuel meets the requirements of Special Publication, SEBU6250, "Caterpillar Machine Fluids Recommendations ".
Cold weather adversely affects the characteristics of the fuel. Refer to the Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold-weather operation.
   
Fuel supply    
Result: The fuel supply is stable.
Proceed to Test Step 7.
Result: The fuel supply is not stable.
Repair: Make the necessary repairs.
Verify that the repair eliminated the problem.
   
Table 2
Troubleshooting Test Steps    Values    Results    
7. Restriction in the Air Inlet and Exhaust System
Inlet air restrictions or exhaust system restrictions can cause a high exhaust temperature.
The Engine Control Module (ECM) may monitor the following parameters in order to calculate an exhaust temperature:
- Barometric pressure
- Intake manifold air temperature
- Engine speed
Certain operating conditions may cause the calculated exhaust temperature to increase to a level that may damage engine components. If a high exhaust temperature occurs, the ECM derates the engine in order to reduce the calculated exhaust temperature. The engine is derated only to a level that allows the calculated exhaust temperature to return to an acceptable level.
A. Ensure that the turbocharger is operating correctly. Periodic inspection and cleaning are recommended for the turbocharger compressor housing (inlet side).
B. Check the air filter restriction indicator. Clean plugged air filters or replace plugged air filters.
C. Check the air inlet and exhaust system for restrictions and/or leaks.
   
Restrictions    
Result: There are restrictions in the air inlet or exhaust system.
Repair:Repair the restrictions or remove the restrictions.
Verify that the repair eliminated the problem.
   If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).