C7.1 Engines and Generator Sets Caterpillar

Power Is Intermittently Low or Power Cutout Is Intermittent

Usage:

C7.1 770

Note: Use this procedure only if the engine does not stop completely.

Probable Causes

Diagnostic codes
Electrical connectors
ECM connection
Intake manifold pressure
Fuel supply
Transfer Pump Inlet Regulator (TPIR) flow
Transfer Pump Inlet Regulator (TPIR) return
Electric Fuel Lift Pump (EFLP) flow
Return fuel lines

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.

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Table 1
Troubleshooting Test Steps	Values	Results
1. Diagnostic Codes A. Establish communication between the electronic service tool and the Electronic Control Module (ECM). Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Download the Warranty Report and the Product Status Report with Histograms before performing any troubleshooting or clearing any diagnostic codes. Note: The downloaded information will be required by the Dealer Solutions Network (DSN) if troubleshooting assistance is needed. C. Use the electronic service tool to check for active or logged codes.	Diagnostic codes	Result: There are active or logged codes. Repair: Troubleshoot any codes before continuing with this procedure. Result: There are no active or logged codes. Proceed to Test Step 2.
2. Electrical Connectors A. Check all electrical connectors for damage. Refer to Troubleshooting, "Electrical Connectors - Inspect". Make sure that all the connector seals are in place and that the connectors have been correctly installed.	Electrical connectors	Result: An electrical connector is damaged. Repair: Repair the electrical connector or replace the electrical connector. Result: A connector seal is displaced or missing or an electrical connector is not correctly installed. Repair: Repair the electrical connector or replace the electrical connector. Result: All electrical connectors are OK. Proceed to Test Step 3.
3. ECM Connection A. Check that the P2/J2 connector is correctly installed. Note: If a fault is suspected with the ECM power or ground connections, refer to Troubleshooting, "Electrical Power Supply - Test".	ECM connection	Result: An ECM connector is not correctly installed. Repair: Repair the electrical connector or replace the electrical connector. Result: Both ECM connectors are correctly installed. Proceed to Test Step 4.
4. Intake Manifold Pressure A. Use the electronic service tool to verify the intake manifold pressure. Turn the start switch to the ON position. The intake manifold pressure must read 0 ± 0.5 kPa (0 ± 0.07 psi).	Intake manifold	Result: The intake manifold pressure does not read 0 ± 0.5 kPa (0 ± 0.07 psi). Repair: Refer to Troubleshooting, "Intake Manifold Air Pressure Is Low". Result: The intake manifold pressure reads 0 ± 0.5 kPa (0 ± 0.07 psi). Proceed to Test Step 5.
5. 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 correctly. 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 6.

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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

Before performing the following fuel system tests, the engine must be run for a minimum of 30 minutes.

Note: When performing the following fuel system tests, the Electric Fuel Lift Pump (EFLP) will only operate for 2 minutes unless the engine is running. If necessary, cycle the keyswitch to reactivate the pump.

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Table 2
Troubleshooting Test Steps	Values	Results
6. 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 8. Result: The fuel flow is less than the minimum limit. Proceed to Test Step 7.
7. Transfer Pump Inlet Regulator (TPIR) Return Test A. Make sure that the TPIR return line is not blocked or kinked. B. Check that the Electric Fuel Lift Pump (EFLP) is operating correctly. C. Make sure that the fuel lines between the EFLP and the TPIR are not blocked or kinked.	TPIR return	Result: A fuel line is blocked or kinked. Repair: Clear the fuel line or replace the fuel line. Result: The EFLP is not operating correctly. Repair: Refer to Troubleshooting, "Relay - Test". Result: All fuel lines are OK and the EFLP appears to be operating correctly. Proceed to Test Step 8.

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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
8. 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 9.
9. 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, contact the Dealer Solutions Network (DSN).