0391124 JOHNSON HOOK, Rear

Probable Causes
Diagnostic codes
Parameters in the Electronic Control Module (ECM)
Electrical connectors
Air intake and exhaust system
Valve lash
Turbocharger (if equipped)
Fuel supply
Low compression (cylinder pressure)Recommended Actions
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.
Note: The procedures have been listed in order of probability. Complete the procedures in order.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.
Table 1
Troubleshooting Test Steps Values Results
1. Diagnostic Codes
Note: Certain diagnostic codes and/or event codes may cause poor performance. Refer to in the electronic service tool.
A. Use the electronic service tool to check for active or logged codes. Engine Derate or Diagnostic Codes Result: A diagnostic code is present.
Troubleshoot the code and then reset the histogram.
Result: A diagnostic code is not present.
Proceed to Test Step 2.
2. Parameters in the Electronic Control Module (ECM)
A. Use the electronic service tool to verify that the correct engine rating has been provided.
B. Use the electronic service tool to verify the maximum engine speed limit.
C. Ensure that the repairs have restored the expected performance. Parameters Result: The parameters are not correct.
Input the correct parameters. Refer to Troubleshooting, "Customer Specified Parameters" for additional information.
Result: The parameters are correct.
Proceed to Test Step 3.
3. Electrical Connectors
A. Turn the keyswitch to the OFF position.
B. Check the engine harness for abrasions and pinch points.
C. Inspect the terminals on the engine sensor connectors. Refer to Troubleshooting, "Electrical Connector - Inspect".
D. Inspect the terminals on the engine ECM connectors. Refer to Troubleshooting, "Electrical Connector - Inspect". Loose connection or damaged wire Result: There is a fault in a connector or the wiring
Repair any faulty connectors or replace the wiring harness. Ensure that all of the seals are properly in place and ensure that the connectors are correctly coupled.
Result: All connectors, pins, and sockets are correctly coupled and/or inserted. The harness is free of corrosion, abrasion, and pinch points.
Proceed to Test Step 4.
4. Air Intake and Exhaust System
A. Check the air filter restriction indicator, if equipped. Replace a plugged air filters. Refer to the Operation and Maintenance Manual.
B. Check the air inlet and exhaust system for restrictions and/or leaks. Restrictions Result: There are restrictions in the air inlet or exhaust system.
Make the necessary repairs, Refer to Systems Operation/Testing and Adjusting, "Air Inlet and Exhaust System - Inspect" for additional information.
Result: There are no restrictions in the air inlet or exhaust system.
Proceed to Test Step 5.
5. Valve Lash
Note: The valve lash can affect the performance of the engine.
A. Check the valve lash. Refer to Systems Operation, Testing, and Adjusting, "Engine Valve Lash - Inspect". Valve lash Result: The valve lash is not set correctly.
Set the valve lash. Refer to Systems Operation, Testing, and Adjusting, "Engine Valve Lash - Inspect/Adjust" for the correct procedure.
Result: The valve lash is correct.
Proceed to Test Step 6.
6. Turbocharger (if equipped)
Note: The turbocharger that is installed on the engine is a nonserviceable item. If any mechanical fault exists, then the faulty turbocharger must be replaced.
A. Ensure that the mounting bolts for the turbocharger are tight.
B. Check that the oil drain for the turbocharger is not blocked or restricted.
C. Check that the compressor housing for the turbocharger is free of dirt and debris. Make sure that the housing is not damaged.
D. Check that the turbine housing for the turbocharger is free of dirt and debris. Make sure that the housing is not damaged.
E. Check that the turbine blades rotate freely in the turbocharger.
F. Ensure that the wastegate on the turbocharger is adjusted correctly. Refer to Systems Operation, Testing, and Adjusting, "Turbocharger - Inspect". If the wastegate actuator is faulty, replace the turbocharger. Refer to Disassembly and Assembly, "Turbocharger - Remove" and Disassembly and Assembly, "Turbocharger - Install". Turbocharger Result: There is a fault on the turbocharger.
Repair the turbocharger or replace the turbocharger. Refer to Disassembly and Assembly, "Turbocharger - Remove" and Disassembly and Assembly, "Turbocharger - Install".
Result: The turbocharger is OK.
Proceed to Test Step 7.
7. Fuel Supply
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.
D. If the temperature is below 0 °C (32 °F), check for solidified fuel (wax).
E. Check the primary filter/water separator for water in the fuel.
F. Check for fuel supply lines that are restricted.
G. Check that the low-pressure fuel lines are tight and secured properly.
H. Check that the Electric Fuel Lift Pump (EFLP) is operating. If the EFLP is suspect, refer to Troubleshooting, "Relay - Test (Electric Fuel Lift Pump)".
I. Replace the primary and secondary fuel filters.
J. Check the diesel fuel for contamination. Refer to Systems Operation, Testing, and Adjusting, "Fuel Quality - Test".
K. Check for air in the fuel system. Refer to Systems Operation, Testing, and Adjusting, "Air in Fuel - Test".
L. Ensure that the fuel system has been primed. Refer to Systems Operation, Testing, and Adjusting, "Fuel System - Prime". Fuel system Result: The fuel supply is not OK.
Repair the fuel system or replace the fuel system components, as necessary.
Result: The fuel supply is OK.
Proceed to Test Step 8.
8. Low Compression (Cylinder Pressure)
A. Perform a compression test. Refer to Systems Operation, Testing, and Adjusting, "Compression - Test ". Cylinder compression Result: The results of the compression test are outside the specifications.
Investigate the cause and rectify any faults.
Note: Possible causes of low compression are shown in the following list:
Loose glow plugs
Faulty piston
Faulty piston rings
Worn cylinder bores
Worn valves
Faulty cylinder head gasket
Damaged cylinder head
Result: The results of the compression test are OK.
Contact the Technical Communicator at a Cat Dealer.