C7.1 Engines For Caterpillar Built Machines Caterpillar

Probable Causes

• Diagnostic codes

• Visible faults

• Air intake and exhaust system

• Speed/timing sensor

• Fuel system

• Glow plugs

• Low compression (cylinder pressure)

Recommended Actions

Diagnostic Codes

Use one of the following methods to check for active diagnostic codes:

• The electronic service tool

• The display on the control panel

Electronic Service Tool

1. Connect the electronic service tool to the diagnostic connector.

2. Check for active diagnostic codes on the electronic service tool.

3. Investigate any active codes before continuing with this procedure. Refer to Troubleshooting, "Troubleshootingwith a Diagnostic Code".

4. Attempt to start the engine. If the engine will not start, proceed to "Visible Faults".

Display on the Control Panel

1. Check the display on the control panel for active diagnostic codes.

2. Troubleshoot any active codes before continuing with this procedure. Refer to Troubleshooting, "Troubleshootingwith a Diagnostic Code".

3. Attempt to start the engine. If the engine will not start, proceed to "Visible Faults".

Visible Faults

1. Visually inspect the engine for the following faults:

   • Missing components

   • Damaged components

   • Damaged electrical cables or loose electrical cables

   • Oil leaks

   • Fuel leaks

2. Check the following items:

   • If the Aftertreatment Regeneration Device (ARD) is operating at a higher frequency than normal, there may be a faulty cylinder in the engine. Refer to "Low Compression (Cylinder Pressure)".

   • Check for the correct level of fuel, oil, and coolant.

   • Ensure that the fuel supply valve (if equipped) is in the OPEN position.

   • If the ambient temperature is below 0 °C (32 °F), use the correct specification of engine oil and oil for the machine.

   • Check that the battery voltage is correct.

   • Use the electronic service tool to check the average cranking speed of the engine. If the cranking speed is less than 150 rpm, investigate the cause of the low cranking speed.

   • Make sure that all fuel filters are correctly installed.

   • Drain any water from the primary fuel filter/water separator.

3. Rectify any faults that are found during the visual checks.

4. Attempt to start the engine. If the engine will not start, proceed to "Air Intake and Exhaust System".

Air Intake and Exhaust System

1. Ensure that the air filter is clean and serviceable.

2. Check the air intake and exhaust systems for the following defects:

   • Blockages

   • Restrictions

   • Damage to lines or hoses

3. Repair any defects before attempting to restart the engine.

4. Attempt to start the engine. If the engine will not start, proceed to "Speed/timing Sensors".

Speed/timing Sensors

1. Disconnect the connector from the primary speed/timing sensor.

2. Attempt to start the engine.

3. If the engine starts, check for a fault in the circuit for the primary speed/timing sensor. Refer to Troubleshooting, "Engine Speed/Timing Sensor Circuit - Test".

4. If the engine does not start, inspect the timing ring on the crankshaft for misalignment.

5. If necessary, repair the timing ring. Refer to Disassembly and Assembly, "Crankshaft Timing Ring - Remove and Install".

6. Connect the electronic service tool to the diagnostic connector.

7. Check that the desired fuel rail pressure is at least 25 MPa (3625 psi) when the engine is cranking.

8. If the desired fuel rail pressure is less than 25 MPa (3625 psi), perform the following procedure:

   1. Use the electronic service tool to check the signal from the secondary speed/timing sensor when the engine is cranking.

   2. If the signal from the secondary speed/timing sensor is 0 rpm, investigate the secondary speed/timing sensor. Refer to Troubleshooting, "Engine Speed/Timing Sensor Circuit - Test".

   3. If a fault is identified in the circuit for the secondary speed/timing sensor, repair the fault and then attempt to start the engine. If the engine will not start, proceed to "Fuel System".

   4. If the signal from the secondary speed/timing sensor is greater than 0 rpm and the engine will not start, proceed to "Fuel System".

Fuel System

1. If the temperature is below 0 °C (32 °F), check for solidified fuel (wax).

2. Check for fuel supply lines that are restricted.

3. Check that the low-pressure fuel lines are correctly installed.

4. Replace the in-line fuel strainer that is installed upstream of the Electric Fuel Lift Pump (EFLP).

5. Check that the EFLP is operating. If the EFLP is suspect, refer to Troubleshooting, "Fuel Pump Relay Circuit - Test".

6. Check the diesel fuel for contamination. Refer to Systems Operation, Testing, and Adjusting, "Fuel Quality - Test".

7. Check for air in the fuel system. Refer to Systems Operation, Testing, and Adjusting, "Air in Fuel - Test".

8. Ensure that the fuel system has been primed. Refer to Systems Operation, Testing, and Adjusting, "Fuel System - Prime".

9. Attempt to start the engine. If the engine will not start, continue with this procedure.

10. Replace the primary fuel filter and the secondary fuel filter. Refer to the Operation and Maintenance Manual, "Fuel System Primary Filter (Water Separator) Element - Replace".

11. Turn the keyswitch to the OFF position and then disconnect the electrical connector from the EFLP.

12. With the keyswitch in the ON position, measure the voltage at the harness connector for the EFLP. The voltage must be between 20 VDC and 28 VDC. If the voltage is below 20 VDC, investigate the cause. Refer to Troubleshooting, "Fuel Pump Relay Circuit - Test".

13. Turn the keyswitch to the OFF position and then reconnect the electrical connector to the EFLP.

14. If a repair has been performed to rectify a low supply voltage to the EFLP, attempt to start the engine. If the engine does not start, continue with this procedure.

    Note: Before performing the following fuel system tests, the engine must be stopped 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.

15. Use the following procedure to check the flow from the Transfer Pump Inlet Regulator (TPIR):
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    Illustration 1	g02522678
    Locations in the low-pressure fuel system (1) Fuel return line to the secondary fuel filter (2) Secondary fuel filter base (3) Transfer Pump Inlet Regulator (TPIR) (4) TPIR return port

    1. Disconnect the TPIR return line from the drain port (4) on the TPIR (3). Install a suitable blanking cap on the open port in the TPIR return line

    2. Connect a temporary drain line to the drain port on the TPIR.

    3. Place the end of the temporary drain line into a suitable calibrated container.

    4. With the keyswitch in the ON position but the engine not running, use a suitable multimeter to measure the input voltage to the EFLP. Record the reading.

    5. With the keyswitch in the ON position but the engine not running, measure the fuel flow from the temporary drain line. Refer to Illustration 2 for the minimum acceptable flow rate.
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       Illustration 2	g02522799
       Minimum TPIR flow rate

    6. Remove the temporary drain line from the drain port on the TPIR. Connect the TPIR return line to the TPIR.

    7. If the fuel flow in Step 15.e is greater than the minimum limit, proceed to Step 18.

    8. If the fuel flow in Step 15.e is below the minimum limit, continue with this procedure.

16. Use the following procedure to check the fuel flow through the return pressure relief valve in the secondary fuel filter base:

    1. Disconnect the return line (1) from the secondary fuel filter base and install a blank on the line. Install a temporary line and a calibrated container to the filter base.

    2. With the keyswitch in the ON position, measure fuel flow from the temporary line.

    3. If the fuel flow is more than 300 mL/min (10.2 oz/min), replace the secondary fuel filter base. Refer to Disassembly and Assembly, "Fuel Filter Base - Remove and Install (Twin Secondary Fuel Filter)".

    4. Remove the temporary line and reconnect the return line.

17. If the secondary fuel filter base has been replaced, attempt to start the engine. If the engine does not start, use the following procedure to check the fuel flow from the EFLP:

    1. Disconnect the fuel inlet from the primary fuel filter. Place the open end of the disconnected line into a calibrated container.

    2. With the keyswitch in the ON position, measure the flow from the fuel line. Refer to Illustration 3 for the minimum acceptable fuel flow.
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       Illustration 3	g02523082
       Minimum EFLP flow rate

    3. If the fuel flow is more than 5% below the acceptable limit, replace the EFLP.

    4. If the fuel flow is more than 5% above the acceptable limit, contact the Technical Communicator at a Cat dealer.

18. Use the electronic service tool to check the absolute fuel rail pressure when the engine is cranking at a minimum speed of 150 rpm.

19. If the measurements taken in the previous steps are acceptable and the engine does not start, continue with the procedure.

20. If the absolute fuel rail pressure is less than 25 MPa (3625 psi), perform the following procedure:

    1. Check that the inlet pressure at the fuel injection pump is greater than 50 kPa (7.25 psi). If the inlet pressure is less than 50 kPa (7.25 psi), repeat the diagnostic process from "Fuel System".

    2. Check for fuel leaks in the high-pressure fuel system. Rectify any fuel leaks and then recheck the pressure in the fuel rail. If the fuel rail pressure is greater than 25 MPa (3625 psi), proceed to test step 21.

    3. Perform a solenoid test on the fuel injection pump. Refer to Troubleshooting, "Solenoid Valve - Test".

    4. If any service has been performed as a result of Step 20.c, attempt to start the engine. If the engine will not start, repeat the diagnostic process from "Diagnostic Codes".

    5. Check the Pressure Limiting Valve (PLV) in the fuel rail for leakage. If the PLV is leaking, replace the valve and recheck the pressure in the fuel rail.

    6. If the PLV in the fuel rail is not leaking, check for fuel in the engine oil system. If fuel is suspected in the oil system, take an engine oil sample for analysis. Refer to the Operation and Maintenance Manual, "Engine Oil Sample - Obtain". If the analysis confirms that there is fuel in the engine oil system, investigate the cause.

    7. If fuel is not found in the oil system, proceed to Test Step 21.

21. If the absolute fuel rail pressure is greater than 25 MPa (3625 psi), perform the following procedure:

    1. Use the electronic service tool to make sure that the status of the electronic unit injectors is not "Disabled". If the injectors are disabled but the injectors have not been intentionally disabled with the electronic service tool, proceed to test step 21.d.

    2. If the electronic unit injectors are not disabled, use the electronic service tool to perform an injector solenoid test. Refer to Troubleshooting, "Injector Solenoid Circuit - Test".

    3. If any service has been performed as a result of Step 21.b, attempt to start the engine. If the engine will not start, proceed to "Glow Plugs".

    4. Make sure that the latest flash file for the application is installed in the ECM. Refer to Troubleshooting, "Flash Programming".

    5. Contact the technical communicator at a Cat dealer.

       Note: This consultation can greatly reduce the repair time.

    6. If the Technical Communicator recommends the use of a test ECM, install a test ECM. Refer to Troubleshooting, "Replacing the ECM".

    7. Attempt to start the engine. If the engine will not start, install the original ECM and then proceed to Test Step 21.j.

    8. If the engine starts normally, reconnect the suspect ECM and then verify that the fault returns when the suspect ECM is installed.

    9. If the engine will not start with the suspect ECM, replace the ECM. Check that the engine starts normally. If the engine starts normally, no further testing is required.

    10. Check the timing of the high-pressure fuel pump. Refer to Systems Operation, Testing, and Adjusting, "Fuel Injection Timing - Check".

    11. If the timing of the high-pressure fuel pump required adjustment and the engine will not start, proceed to "Glow Plugs".

    12. If the timing of the high-pressure fuel pump was correct, replace the high-pressure fuel pump. If the engine will not start, proceed to "Glow Plugs".

Glow Plugs

Note: Faulty glow plugs will only affect engine starting when the ambient temperature is between 5° C (41° F) and −25° C (−13° F).

1. Check the operation of the glow plugs. Refer to Troubleshooting, "Glow Plug Starting Aid - Test".

2. If necessary, replace any faulty glow plugs. Refer to Disassembly and Assembly, "Glow Plug - Remove and Install".

3. Attempt to start the engine. If the engine will not start, proceed to "Low Compression (Cylinder Pressure)".

Low Compression (Cylinder Pressure)

1. Perform a compression test. Refer to Systems Operation, Testing, and Adjusting, "Compression - Test".

2. If low compression is noted on any cylinders, investigate the cause and rectify the cause.

   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

3. Perform all necessary repairs.

4. Ensure that the repairs have eliminated the fault.

5. If the fault is still present, contact the technical communicator at the Cat dealer.