G3512E Generator Set Engine Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the fuel metering valve. Also use this procedure if one of the diagnostic codes in Table 1 is active or easily repeated.

The fuel metering valve is an electronic gas valve that controls the flow of fuel to the engine. The valve works with the engine ECM in order to ensure the correct flow of gas in all conditions of engine operation.

The valve converts the command signal and the information into a valve position that directly corresponds to the desired gas flow. The position of the valve is compensated by these additional factors that are internal to the valve:

• A signal for absolute fuel pressure

• Differential pressure across the valve

• Fuel temperature sensors

Communications

The ECM sends the following information to the fuel metering valve via the CAN data link:

• Specific gravity of the fuel

• Specific Heat Ratio of the fuel

• Desired fuel flow rate

The fuel metering valve sends the following information to the ECM via the CAN data link:

• Position of the fuel valve

• Absolute fuel pressure

• Differential pressure across the valve

• Fuel temperature

If the ECM and the fuel metering valve cannot communicate via the CAN data link, a 1446-9 diagnostic code is activated. If the engine is running, the fuel metering valve will use the command signal from the PWM signal. The engine will continue to run. However, if the engine is not running and a 1446-9 diagnostic code becomes active, the ECM will not allow the engine to start.

PWM Signal

The ECM sends a command signal for the fuel flow via a PWM signal. If the PWM signal for the flow of fuel is interrupted, a 1446-8 diagnostic code will be activated. If the engine is running and using the PWM signal when the 1446-8 code is set the fuel metering valve will look to the CAN data link. If the signal is not available on the CAN data link the engine will shut down.

Note: If an open circuit is suspected in the circuit between the power supply and the powered component also inspect the power distribution box for the following conditions:

• Abrasion of the insulation on the wiring within the box

• Damage to the posts for the wiring to the circuit breakers

• Damage to the internal parts of the circuit breakers

Those conditions can contribute to the following difficulties with operation:

• Unstable engine performance

• Interruption of communication between the engine ECM, the fuel metering valve, the actuator for the compressor bypass, and the throttle actuator

• Intermittent loss of power to the ECM

• Intermittent diagnostic codes for conditions such as engine overspeed and lack of communication between electronic components

• Unexpected engine shutdown

Illustration 1	g02310774
Schematic for the components that are related to the fuel metering valve

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Set the engine control switch to the OFF/RESET position. Remove the electrical power from the engine.

2. Thoroughly inspect all connectors, wiring, and terminations for fuel metering valve circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect".
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   Illustration 2	g01767353
   Terminal connections at the P1 connector that are for the fuel metering valve (P1-34) CAN data link − (P1-42) CAN shield (P1-50) CAN data link + (P1-58) Fuel command (PWM) (P1-60) Return

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   Illustration 3	g02150201
   Terminal connections at the harness connector for the fuel metering valve (Terminal F) Keyswitch (Terminal K) Fuel command (PWM) (Terminal L) Return (Terminal T) CAN data link + (Terminal U) CAN data link − (Terminal V) CAN shield (Terminal W) +Battery (Terminal Y) Shield (Terminal Z) −Battery

3. Perform a 45 N (10 lb) pull test on each of the wires in the circuit for the fuel metering valve.

4. Check the torque of the allen head screws for each of the ECM connectors and of the engine interface connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

Expected Result:

All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.

Results:

• OK - The connectors, wiring, and fuses appear to be OK. Proceed to Test Step 2.

• Not OK - The connectors, wiring, circuit breakers, and fuses are not OK.

  Repair: Repair the problem. Replace parts, if necessary. Verify that the repair has eliminated the original problem.

  STOP

Test Step 2. Check for Diagnostic Codes

1. Connect the Caterpillar Electronic Technician (ET) to the service tool connector.

2. Restore the electrical power to the engine. Set the engine control switch to the STOP position.

3. Use the "Active Diagnostic" screen on Cat ET. Look for these codes:

   Note: Monitor the active diagnostic code and the logged diagnostic codes on Cat ET. Wait at least 30 seconds in order for diagnostic codes to become active.

   • 1446-8

   • 1446-9

   • 1446-12

   • 1446-13

   • 1447-12

Results:

• OK - There are no active diagnostic codes.

  Repair: The signal and the communication between the ECM and the fuel metering valve appear to be OK at this time. If one of these codes is logged, there may be an intermittent problem with one of the circuits. If there is a logged code, or an intermittent electrical problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for information that is related to troubleshooting intermittent electrical problems.

  STOP

• Active 1446-8 - The problem may be in the circuit for the PWM signal between the ECM and the fuel metering valve. Proceed to Test Step 3.

• Active 1446-9 - The engine ECM has detected a problem with the communication between the ECM and the fuel metering valve. There may be a problem with the power circuit for the valve, or there may be a problem with communications on the data link. Proceed to Test Step 4.

• Active 1446-12 - There is an active 1446-12 diagnostic code.

  Repair: The fuel metering valve has detected an internal malfunction. Replace the valve.

  STOP

• Active 1446-13 - There is an active 1446-13 diagnostic code.

  Repair: The fuel metering valve factory calibration is lost. Replace the valve.

  STOP

• Active 1447-12 - There is an active 1447-12 diagnostic code.

  Repair: There is a malfunction of the sensor module in the fuel metering valve. Replace the valve.

  STOP

Test Step 3. Check the PWM Circuit for the Fuel Command

1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

2. Disconnect the J1/P1 ECM connectors and the harness connector for the fuel metering valve.

3. Check for continuity between the points that are listed in Table 2. During each measurement, wiggle the wires in the harness in order to check for an intermittent problem. Be sure to wiggle the wires near each of the connectors.
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   Table 2

   Points to Check for Continuity
   Connector and Terminal	Connector and Terminal
   P1-58	Terminal K at the harness connector for the valve
   P1-60	Terminal L at the harness connector for the valve
   P1-58	ECM ground strap

Expected Result:

Both of the wires have continuity. Terminal P1-58 is not shorted to ground.

Results:

• OK - All of the measurements are within the specifications. The wiring appears to be OK.

  Repair: Perform the following procedure:

  1. Connect the J1/P1 ECM connectors. Connect the harness connector for the fuel metering valve.

  2. Restore the electrical power to the engine. Start the engine and run the engine. Check for an active 1446-8 code.

     If the code does not recur, the problem appears to be resolved. The original problem was probably caused by a poor electrical connection. Refer to Troubleshooting, "Electrical Connectors - Inspect" for information that is related to troubleshooting intermittent electrical problems.

  3. If the 1446-8 code remains active, there may be a problem with the ECM or with the fuel metering valve. Perform the following procedure:

  4. Temporarily install a new ECM. Refer to Troubleshooting, "ECM - Replace". If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the original ECM. Refer to Troubleshooting, "ECM - Replace". If the problem is not resolved with a new ECM, install the original ECM. Continue with this procedure.

  5. Temporarily install a new fuel metering valve. If the new fuel metering valve operates correctly, the problem is resolved. If the new fuel metering valve does not operate correctly, install the original fuel metering valve. Retest the system.

  STOP

• Not OK - At least one of the measurements is incorrect.

  Repair: There is a problem with the wiring between the ECM and the fuel metering valve. Repair the connector and/or the wire, when possible. Replace parts, if necessary.

  STOP

Test Step 4. Check for Electrical Power at the Fuel Metering Valve

1. Refer to Illustration 1. Measure the voltage for the fuel metering valve at the engine power distribution box.

   The battery voltage must be between 18 V and 32 V in order for the fuel metering valve to operate correctly. If a problem exists, correct the problem before you continue.

2. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

3. Disconnect the harness connector for the fuel metering valve.

4. Set the engine control to the STOP mode. Switch the 35 amp circuit breaker ON.

5. At the harness connector for the valve, measure the voltage at the following terminals:

   • F and Z (keyswitch power)

   • W and Z (battery power)

Results:

• OK - Both voltages at the harness connector are within 2 V of the voltage at the engine power distribution box. Proceed to Test Step 5

• Not OK - At least one of the voltages are not within 2 V of the voltage at the engine power distribution box.

  Repair: The fuel metering valve is not receiving the proper operating voltage. There is a problem in the harness or in a connector. Determine the cause of the excessive voltage drop. Perform the necessary repairs. Verify that the repair eliminates the original problem.

  STOP

Test Step 5. Check the Resistance of the CAN Data Link at the Harness Connector for the Fuel Metering Valve

Note: When the resistance measures between 114 Ohms and 126 Ohms, one of the resistors is not properly connected into the circuit.

1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

2. Disconnect the harness connector for the fuel metering valve.

3. Measure the resistance between terminals P24-T (CAN data link +) and P24-U (CAN data link -).

Results:

• OK - The resistance is between 57 and 63 Ohms. Proceed to Test Step 6

• Not OK - The resistance is not between 57 Ohms and 63 Ohms.

  Repair: Ensure that 2 termination resistors of the correct value are in place and properly connected to the circuit.

  Proceed to Test Step 6

Test Step 6. Check the Resistance of the CAN Data Link at the P1 ECM Connector

Note: Some devices will be spliced into the harness at different locations. Therefore also verify the correct resistance at the ECM. The ECM is the device the components are communicating with and the device that is presenting the code. Measure resistance at the ECM and check for continuity with the suspect device on the data link.

1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

2. Disconnect the ECM J1/P1 connectors.

3. Measure the resistance between terminals P1-50 (CAN data link +) and P1-34 (CAN data link -).

Results:

• OK - The resistance is between 57 and 63 Ohms. Proceed to Test Step 7

• Not OK - The resistance is not between 57 Ohms and 63 Ohms.

  Repair: Ensure that 2 termination resistors of the correct value are in place and properly connected to P1-50 and P1-34.

  Proceed to Test Step 7

Test Step 7. Check the Continuity of the Wiring Harness for the CAN Data Link

1. Use a multimeter to check for continuity between the points that are listed in Table 3.
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   Table 3

   Points to Check for Continuity
   Connector and Terminal	Connector and Terminal
   P1-34	P24-U
   P1-50	P24-T
   P1-34	Ground strap for the ECM
   P1-50	Ground strap for the ECM

Results:

• OK - There is continuity between the terminals of the connectors and there is no continuity between the terminals and the ground strap. Proceed to Test Step 8.

• Not OK - There is an open circuit between the terminals of the connectors or there is a short between the terminals and the ground strap.

  Repair: Perform the necessary repairs to the wiring and/or connectors. Replace parts, if necessary. Ensure that all of the seals are properly installed. Ensure that the connectors are properly engaged. Verify that the repair has eliminated the original problem.

  STOP

Test Step 8. Check the Harness for a Short Circuit

1. Measure the resistance between the points that are listed in Table 4. Be sure to wiggle the wires in the harnesses as you make each resistance measurement.
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   Table 4

   Resistance Measurements for the CAN Data Link
   Connector and Terminal	Terminal
   P1-50 (CAN data link +)	All of the other terminals on the P1 connector
   	ECM ground strap
   P1-34 (CAN data link -)	All of the other terminals on the P1 connector
   	ECM ground strap

Results:

• OK - Each check of the resistance indicates an open circuit. The harness is not shorted. Proceed to Test Step 9.

• Not OK - At least one check of the resistance indicates that there is continuity in the circuit.

  Repair: There is a short circuit in a harness. There may be a problem with a connector. Repair the wiring and/or the connector. Replace part, if necessary. Restore the wiring to the original configuration. Verify that the problem is resolved.

  STOP

Test Step 9. Determine if the ECM is the Problem

1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

2. Temporarily install a new ECM.

3. Connect the fuel metering valve.

4. Restore electrical power.

5. Check for proper operation.

Results:

• OK - The new ECM resolved the problem.

  Repair: If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the original ECM. Refer to Troubleshooting, "ECM - Replace"

  STOP

• Not OK - The new ECM did not resolve the problem. Proceed to Test Step 10

Test Step 10. Determine if the Fuel Metering Valve is the Problem

1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

2. Temporarily install a new fuel metering valve.

3. Restore electrical power.

4. Check for proper operation.

Results:

• OK - The new valve resolved the problem.

  Repair: Permanently install the new fuel metering valve.

  STOP

• Not OK - The problem is not resolved.

  Repair: Retest the system.

  STOP