3412, 3412C, and 3412E Generator Set Engines Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the circuit for the fuel control solenoid or if one of the diagnostic codes in Table 1 is active or easily repeated.

The Electronic Control Module (ECM) contains the logic and the outputs for control of starting the engine and stopping the engine. Some of the logic for starting the engine and for stopping the engine is customer programmable. The logic responds to inputs from the following components: engine control switch, emergency stop switch and other inputs.

The ECM outputs a signal to the fuel control solenoid in order to control the fuel shutoff valve. To enable fuel flow to the engine, the fuel control solenoid must be energized. The fuel control solenoid may be controlled by the ECM or by the customer's equipment. Use this procedure to troubleshoot either configuration.

The most likely cause of a diagnostic code is a poor electrical connection or a problem in a wiring harness. The next likely cause may be a problem with the fuel control solenoid. The least likely cause is a problem with the ECM.

The following information describes the system's operation when the fuel shutoff valve is controlled by the ECM:

The ECM sends an output signal to the fuel control solenoid that controls the operation of the fuel shutoff valve. This output is energize-to-run. During the crank cycle, when the engine speed exceeds 50 rpm, the ECM provides a voltage of +Battery to the output for the fuel control solenoid. The solenoid becomes energized. This initiates fuel flow to the engine. The ECM removes the voltage from this output in order to stop the engine. The fuel control solenoid becomes de-energized. This stops the fuel flow.

Illustration 1	g01627351

Illustration 2	g01635794
(22) Fuel shutoff solenoid (33) Solenoid ground

Test Step 1. Inspect the Electrical Connectors and the Wiring Harness

1. Remove electrical power from the ECM.

2. Thoroughly inspect the P5/J5 connector for the fuel shutoff solenoid. Inspect the ECM J14/P14 connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the fuel shutoff solenoid.

4. Check the allen head screw on the ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

• OK - The connectors and wiring are OK. Proceed to Test Step 2.

• Not OK - There is a problem with the connectors and/or the wiring.

  Repair: Repair the wiring and connectors or replace the wiring or the connectors. Ensure that all of the seals are properly connected. Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check the Engine Start-up

1. Turn the engine control switch to the ON position. The engine should remain in the OFF position.

   Note: The solenoid should make an audible sound when the solenoid is first energized.

2. Attempt to start the engine.

Expected Result:

The engine will start and the engine will run.

Results:

• OK - The engine will start and the engine will run. Proceed to Test Step 3.

• NOT OK - The engine will not start and the engine will not run. Proceed to Test Step 4.

Test Step 3. Check the Engine Shutdown

1. Turn the engine control switch to the OFF position.

Expected Result:

The engine should shut down.

Results:

• OK - The engine shuts down.

  Repair: The fuel shutoff solenoid is working properly. Refer to Troubleshooting, "Electrical Connectors - Inspect" for a intermittent problem.

  STOP

• NOT OK - The engine does not shut down.

  Repair: Check the linkage for binding. Also, check the plunger for the fuel shutoff solenoid for binding.

  STOP

Test Step 4. Override the Shutoff Solenoid with the Manual Shutoff Lever

1. Rotate the manual shutoff lever in a clockwise direction. This will override the shutoff solenoid.

2. Turn the engine control switch to the ON position.

3. Attempt to start the engine while the manual shutoff lever is held in the clockwise position.

Expected Result:

The engine should start and the engine should run while the lever is held in the clockwise position.

Results:

• OK - The engine starts and the engine runs while the manual shutoff lever is held in the clockwise position. Proceed to Test Step 5.

• NOT OK - The engine will not start. The fuel shutoff valve is not the problem.

  Repair: The fuel shutoff valve is not the problem. Refer to Troubleshooting, "Engine Cranks but Does Not Start" for more troubleshooting information.

  STOP

Test Step 5. Check the Solenoid Coil for Shorts or Opens.

1. Disconnect J5/P5 connector.

2. Measure the resistance from connector J5-A to connector J5-B.

3. Measure the resistance from connector J5-A and engine ground.

Expected Result:

The resistance from connector J5-A to connector J5-B is between 0.8 and 2.0 Ohms. The resistance from connector J5-A and engine ground is greater than 20,000 Ohms.

Results:

• OK - The resistance from connector J5-A to connector J5-B is between 0.8 and 2.0 Ohms. The resistance from connector J5-A and engine ground is greater than 20,000 Ohms. Proceed to Test Step 6.

• NOT OK - The resistance from connector J5-A to connector J5-B is not between 0.8 and 2.0 Ohms or the resistance from connector J5-A and engine ground is less than 20,000 Ohms.

  Repair: The fuel shutoff solenoid is faulty. Replace the fuel shutoff solenoid.

  STOP

Test Step 6. Check for Shorts in the Harness

1. Turn the engine control switch to the OFF position.

2. Disconnect connector J14/P14 and disconnect connector J5/P5.

3. Measure the resistance between connector pins P5-A and P5-B.

4. Measure the resistance between connector pin P5-A and engine ground.

5. Measure the resistance between connector pin P5-B and engine ground.

Expected Result:

The resistance reading is more than 20,000 Ohms for each measurement.

Results:

• OK - The resistance reading is more than 20,000 Ohms for each measurement. Proceed to Test Step 7.

• Not OK - The resistance reading is less than 20,000 Ohms for any measurement.

  Repair: There is an open circuit in the engine harness or the customer supplied wiring. Repair the harness or replace the harness. as required.

  STOP

Test Step 7. Check Resistance through the Harness

1. Attach Deutsch terminals to a wire at each end.

2. Attach the wire to P5-A and P5-B. This will short the wires to the solenoid.

3. Measure the resistance between P14-33 and P14-22.

Expected Result:

The resistance is less than 10 Ohms.

Results:

• OK - The resistance is less than 10 Ohms. Proceed to Test Step 8.

• NOT OK - The resistance is more than 10 Ohms.

  Repair: There is an open circuit in the engine harness or the customer supplied wiring. Repair the harness or replace the harness.

  STOP

Test Step 8. Check for Solenoid Voltage at the ECM

1. Reconnect all connectors.

2. Measure the voltage between P14-33 and P14-22 while the engine is cranking.

Expected Result:

The voltage rises over 4 VDC while the engine is cranking. The voltage is between 2.5 and 1.5 VDC within five seconds of the engine starting.

Results:

• OK - The voltage rises over 4 VDC while the engine is cranking. The voltage is between 2.5 and 1.5 VDC within 5 seconds of the engine starting. Proceed to Test Step 9.

• NOT OK - The voltage does not rise over 4 VDC while the engine is cranking. The voltage is not between 2.5 and 1.5 VDC within 5 seconds of the engine starting.

  Repair: Check the ECM for proper supply voltage. Refer to Troubleshooting, "Electrical Power Supply - Test". If the voltage to the ECM is correct, replace the ECM.

  STOP

Test Step 9. Check for Voltage at the Shutoff Solenoid

1. Rotate the manual shutoff lever in the clockwise direction.

2. Measure the voltage between J5-A and J5-B while the engine is cranking.

Expected Result:

The voltage rises over 4 VDC while the engine is cranking. The voltage is between 2.5 and 1.5 VDC within five seconds of the engine starting .

Results:

• OK - The voltage rises over 4 VDC while the engine is cranking. The voltage is between 2.5 and 1.5 VDC within five seconds of the engine starting .

  Repair: Check the linkage and the plunger for binding.

  STOP

• NOT OK - The voltage does not rise over 4 VDC while the engine is cranking. The voltage is not between 2.5 and 1.5 VDC within five seconds of the engine starting .

  Repair: The voltage is correct at the ECM but not at the solenoid. The problem is in the harness.

  STOP