C7.1 Engines and Generator Sets Caterpillar

Engine Stalls at Low RPM

Usage:

C7.1 770

Probable Causes

Diagnostic codes
Accessory equipment
Power mode control (if equipped)
Fuel supply
Low compression (cylinder pressure)
Electronic unit injectors

Table 1
Troubleshooting Test Steps	Values	Results
1. Diagnostic Codes A. Establish communication between the electronic service tool and the Electronic Control Module (ECM) . If necessary, refer to Troubleshooting, "Electronic Service Tools". B. Check if any codes are active or logged.	Diagnostic code	Result: A code is active or logged. Repair: Troubleshoot any codes before continuing with this procedure. Result: A code is not active or logged. Proceed to Test Step 2.
2. Accessory Equipment A. Check all accessory equipment for faults that may create excessive load on the engine.	Accessories	Result: An engine accessory is creating an excessive load. Repair: Repair or replace the engine accessory. Result: An engine accessory is not creating an excessive load. Proceed to Test Step 3.
3. Power Mode Control (If Equipped) A. Check whether the power mode control is using the Cat data link or the CAN data link and then use the appropriate test. Refer to Troubleshooting, "Data Link - Test" or Troubleshooting, "CAN Data Link - Test". B. Check the engine wiring harness for defects. Refer to Troubleshooting, "Electrical Connectors - Inspect".	Power mode control	Result: There is a fault in the data link. Repair: Repair the data link, as necessary. Result: There is a wiring fault. Repair: Repair or replace the wiring, as necessary. Result: The data link and the wiring are OK. Proceed to Test Step 4.
4. Fuel Supply A. Ensure that the vent in the fuel cap is not filled with debris. B. Ensure that the fuel supply valve (if equipped) is in the full OPEN position. C. If the temperature is below 0 °C (32 °F), check for solidified fuel (wax). D. Check the primary filter/water separator for water in the fuel. E. Check for fuel supply lines that are restricted. F. Replace the in-line fuel filter that is installed upstream of the Electric Fuel Lift Pump (EFLP). G. Check that the EFLP is operating correctly. H. Replace the primary and secondary fuel filters. I. Check the diesel fuel for contamination. Refer to Systems Operation, Testing, and Adjusting, "Fuel Quality - Test". J. Check for air in the fuel system. Refer to Systems Operation, Testing, and Adjusting, "Air in Fuel - Test".	Fuel system	Result: The vent in the fuel cap is blocked. Repair: Install a replacement fuel cap. Result: The fuel contains solidified wax. Repair: Replace the fuel with fuel of the correct specification for the ambient conditions. Result: There are fuel supply lines that are restricted. Repair: Replace any damaged or restricted fuel lines. The EFLP is suspect. Refer to Troubleshooting, "Fuel Pump Relay Circuit - Test". Replace the primary fuel filter and the secondary fuel filters. Refer to the Operation and Maintenance Manual for further information. Result: There is air in the fuel system. Repair: Prime the fuel system. Refer to Systems Operation, Testing, and Adjusting, "Fuel System - Prime". Result: The diesel fuel is contaminated. Repair: Drain the fuel tank and the fuel system. Replace the primary fuel filter and the secondary fuel filters. Refer to the Operation and Maintenance Manual for further information. Fill and prime the fuel system with fuel of the correct specification. Refer to Systems Operation, Testing, and Adjusting, "Fuel System - Prime". Result: The fuel supply is OK. Proceed to Test Step 5.
5. 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. Repair: 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. Proceed to Test Step 6.

Contact with high pressure fuel may cause fluid penetration and burn hazards. High pressure fuel spray may cause a fire hazard. Failure to follow these inspection, maintenance and service instructions may cause personal injury or death.

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NOTICE

Contact with high-pressure fuel may cause personal injury or death. Wait 10 minutes after the engine has stopped to allow fuel pressure to purge before any service or repair is performed on the engine fuel lines.

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Table 2
Troubleshooting Test Steps	Values	Results
6. Electronic Unit Injectors A. Use the electronic service tool to perform the automatic "Cylinder Cut Out Test". Note: If the compression test that was performed in Test Step 5 was satisfactory, the "Cylinder Cut Out Test" will identify any faulty injectors.	Electronic Unit Injectors	Result: A faulty injector is indicated. Repair: Remove any faulty electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove". Install new electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector - Install". Repeat the automatic "Cylinder Cut Out Test". If the fault is still apparent, remove the replacement electronic unit injector and install the original electronic unit injector. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove" and Disassembly and Assembly, "Electronic Unit Injector - Install". Result: All injectors are OK. Contact the Dealer Solutions Network (DSN).