C7.1 Engines Caterpillar

Acceleration Is Poor or Throttle Response Is Poor

Usage:

C7.1 881

Probable Causes

Diagnostic codes
Parameters in the Electronic Control Module (ECM)
Electrical connectors
Air intake and exhaust system
Valve lash
Turbocharger or turbochargers
Fuel supply
Low compression (cylinder pressure)
Electronic unit injectors
Individual malfunctioning cylinder

Recommended Actions

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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.

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.

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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. B. Use the electronic service tool to check the histogram information if the engine has been derated. Note: If the histograms contain engine derates and no diagnostic codes are present, then the engine is operating normally.	Engine Derate or Diagnostic Codes	Result: A diagnostic code is present. Repair: 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 parameters are being used. Refer to Troubleshooting, "Configuration Parameters" for additional information.	Parameters	Result: The parameters are not correct. Repair: Input the correct parameters. Refer to Troubleshooting, "Configuration Parameters" for additional information. Result: The parameters are correct. Proceed to Test Step 3.
3. Electrical connectors A. Turn the start switch to the ON position. B. Use the electronic service tool to check the intake manifold pressure. C. Run the engine until the speed is equal to the maximum no-load speed. D. Use the electronic service tool to make sure that the throttle is set to reach the maximum no-load speed.	Electrical connections	Result: The intake manifold pressure is not zero ± 0.5 kPa (zero ± 0.070 psi). Repair: Check the 5 VDC sensor supply for the intake manifold pressure. Refer to Troubleshooting, "Sensor Supply - Test". Result: The throttle response is not as expected. Repair: If the maximum no-load speed cannot be obtained refer to Troubleshooting, "Switch Circuits - Test" and Troubleshooting, "Mode Selection - Test". If the engine speed is erratic refer to Troubleshooting, "Speed Control - Test". Result: All responses are normal. Proceed to Test Step 4.
4. Air Intake and Exhaust System A. Observe the check engine lamp. Check for an 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. Repair: 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.	Valve lash	Result: The valve lash is not correct. Repair: Check the valve lash. Refer to Systems Operation, Testing, and Adjusting, "Engine Valve Lash - Inspect" for the correct procedure. Result: The valve lash is correct. For engines with a single turbocharger, proceed to Test Step 6. For engines with twin turbochargers, proceed to Test Step 7.
6. Turbocharger This Test Step is applicable to engines with a single turbocharger. 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: 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 8.
7. Turbochargers This Test Step is applicable to engines with twin turbochargers. Note: The turbochargers that are installed on the engine are nonserviceable items. If any mechanical fault exists, then the faulty turbocharger must be replaced. A. Ensure that the mounting bolts for the turbochargers are tight. B. Check that the oil drains for the turbochargers are not blocked or restricted. C. Check that the compressor housings for the turbochargers are free of dirt and debris. Make sure that the housings are not damaged. D. Check that the turbine housings for the turbochargers are free of dirt and debris. Make sure that the housings are not damaged. E. Check that the turbine blades rotate freely in the turbochargers. F. Ensure that the wastegate on the high-pressure turbocharger is adjusted correctly. Refer to Systems Operation, Testing, and Adjusting, "Turbocharger - Inspect". If the wastegate actuator is faulty, replace the high-pressure turbocharger. Refer to Disassembly and Assembly, "Turbocharger - Remove" and Disassembly and Assembly, "Turbocharger - Install".	Turbochargers	Result: There is a fault on one of the turbochargers. Repair: Repair the faulty turbocharger or replace the faulty turbocharger. Refer to Disassembly and Assembly, "Turbocharger - Remove" and Disassembly and Assembly, "Turbocharger - Install". Result: The turbochargers are OK. Proceed to Test Step 8.
8. 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, "Fuel Transfer Pump - Test". I. Replace the in-line fuel filter that is upstream of the primary fuel filter. J. Replace the primary and secondary fuel filters. K. Check the diesel fuel for contamination. Refer to Systems Operation, Testing, and Adjusting, "Fuel Quality - Test". L. Check for air in the fuel system. Refer to Systems Operation, Testing, and Adjusting, "Air in Fuel - Test". M. 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: Repair the fuel system or replace the fuel system components, as necessary. Result: The fuel supply is OK. Proceed to Test Step 9.

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Illustration 1	g03750256
Transfer Pump Inlet Regulator (TPIR) components (1) Transfer Pump Inlet Regulator (TPIR) (2) TPIR return port

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Illustration 2	g02355128
Minimum TPIR flow rate in a 12 VDC system

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Illustration 3	g02355130
Minimum TPIR flow rate in a 24 VDC system

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Table 2
Troubleshooting Test Steps	Values	Results
9. Transfer Pump Inlet Regulator (TPIR) Flow Test Refer to Illustration 1. A. Disconnect the TPIR return line from the drain port on the TPIR. Install a suitable blanking cap on the open port in the TPIR return line. B. Connect a temporary drain line to the drain port on the TPIR. C. Place the end of the temporary drain line into a suitable calibrated container. D. With the isolator switch in the ON position but the engine not running, use a suitable multimeter to measure the input voltage to the EFLP. Record the reading. E. With the isolator switch in the ON position but the engine not running, measure the fuel flow from the temporary drain line. F. Refer to Illustration 2 or 3for the minimum acceptable flow rate. G. Remove the temporary drain line from the drain port on the TPIR. Connect the TPIR return line to the TPIR.	TPIR flow rate	Result: The fuel flow is greater than the minimum limit. Proceed to Test Step 11. Result: The fuel flow is less than the minimum limit. Proceed to Test Step 10.

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Illustration 4	g02527498
Minimum EFLP flow rate in a 12 VDC system

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Illustration 5	g02527518
Minimum EFLP flow rate in a 24 VDC system

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Table 3
Troubleshooting Test Steps	Values	Results
10. EFLP Flow Test at the Primary Fuel Filter Inlet A. Make sure the keyswitch is in the OFF position. B. Disconnect the fuel inlet connection from the primary fuel filter head. C. Install a suitable blank on the fuel inlet port on the primary fuel filter head. D. Place the open end of the fuel inlet line in a suitable calibrated container. E. With the keyswitch in the ON position, measure the input voltage at the EFLP. Record the result. F. With the keyswitch in the ON position, measure the flow from the fuel inlet line. Record the result. G. Check the recorded voltage and fuel flow on the graph in Illustration 4 or 5.	EFLP flow	Result: The fuel flow is below the minimum value for the recorded voltage. Repair: Replace the EFLP. Refer to Disassembly and Assembly, "Fuel Priming Pump - Remove and Install ". Result: The fuel flow is above the minimum value for the recorded voltage. Proceed to Test Step 11.
11. Check the Return Fuel Lines A. Make sure that the TPIR return line is not blocked or kinked.. B. If the TPIR return line is clear, confirm that the Electric Fuel Lift Pump (EFLP) is operating. Make sure that fuel lines between the EFLP and the TPIR are not blocked or kinked.	Return lines	Result: The TPIR return line or the fuel lines between the EFLP and the TPIR are blocked or kinked. Repair: Clear or replace the blocked line. Result: The TPIR return line and the fuel lines between the EFLP and the TPIR are clear. Repair: Replace the EFLP. If the fault is still present, proceed to Test Step 12.
12. 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 13.

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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 4
Troubleshooting Test Steps	Values	Results
13. 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 12 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. Proceed to Test Step 14.
14. Individual Malfunctioning Cylinders A. With the engine speed at a fast idle, use the electronic service tool to perform the manual "Cylinder Cut Out Test". As each cylinder is cut out, listen for a change in the sound from the engine. When a cylinder is cut out, there should be a noticeable change in the sound of the engine. If a change in the sound of the engine is not noted, the isolated cylinder is not operating under normal conditions. If the isolation of a cylinder results in a change in the sound that is less noticeable, the cylinder may be operating below normal performance.	Cylinders	Result: The test indicates a faulty cylinder. Repair: Investigate the cause of the fault on any cylinder that is not operating. Investigate the cause of the fault on any cylinder that is operating below normal performance. Result: The test indicates that all cylinders are OK. Contact the Dealer Solutions Network (DSN).