The Electronic Control Module (ECM) monitors the generator's output power in order to accurately control the air/fuel ratio. The ECM uses an output from one of the following sources in order to monitor the generator's output power:
- Electronic Modular Control Panel II+ (EMCP II+)
- Programmable Logic Controller (PLC)
- Wattmeter
The PLC and the wattmeter are also called power sensors.
The following probable causes apply if the generator is equipped with the EMCP II+:
- There is an incorrect calibration value for the AC Transformer Box + (ATB+).
- A potential transformer in the ATB+ is faulty.
- A current transformer in the ATB+ is faulty.
- The ATB+ is faulty.
- There is an incorrect value for one or more of the parameters for the fuel.
- There is an incorrect value for one or more of the "Power Monitoring" parameters.
The following probable causes apply if the generator is equipped with a power sensor:
- There is a faulty potential transformer for the power sensor.
- There is a faulty current transformer for the power sensor.
- The power sensor is faulty.
- There is a problem with the wiring between the power sensor and the ECM.
- There is an incorrect value for one or more of the parameters for the fuel.
- The offset voltage at the input to the ECM from the power sensor is too high.
- There is an incorrect value for one or more of the "Power Monitoring" parameters.
Read the rest of this procedure before you adjust the "Power Monitoring" parameters.
Generators that are Equipped with EMCP II+
Verify that the transformers and the ATB+ are operating correctly. Refer to the appropriate service literature for the EMCP II+.
Verify that the values for the "Air/Fuel Ratio Control" configuration parameters are correct. Refer to Troubleshooting, "Electronic Control System Parameters".
Verify that the values for the "Power Monitoring" configuration parameters are correct. Refer to Troubleshooting, "Electronic Control System Parameters".
Generators that are Equipped with a Power Sensor
Verify that the transformers for the power sensor are operating correctly. Refer to the service literature for the power sensor.
Verify that the power sensor is operating correctly. Refer to the service literature for the power sensor.
Verify that the values for the "Air/Fuel Ratio Control" configuration parameters are correct. Refer to Troubleshooting, "Electronic Control System Parameters".
Check the wiring between the power sensor and the ECM for corrosion and for pinch points. Refer to Troubleshooting, "Inspecting Electrical Connectors".
The ECM must receive an accurate voltage from the power sensor. If the voltage is not accurate, the ECM may not accurately control the air/fuel ratio. When the generator's output is zero, the voltage from the power sensor must be less than 0.01 VDC. This voltage is called the offset voltage.
Use the following procedure in order to determine if the offset voltage is too high. Perform this procedure before you adjust the "Power Monitoring" parameters.
Note: This measurement must be taken at the ECM P1 connector. The engine must be stopped.
- If the engine is running, stop the engine.
- Insert 7X-1710 Multimeter Probes into terminals P1-19 and P1-25. Connect a digital voltmeter to the probes. The polarity of the connections is not important.
- Verify that the probes are making good contact with the terminals inside the connector. Measure the DC voltage at the terminals.
The voltage is acceptable if the voltage is less than ±0.01 VDC.
If the voltage is less than ±0.01 VDC, the values for the "Power Monitoring" parameters may be incorrect. Refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters".
If the voltage is greater than ±0.01 VDC, the circuit between the power sensor and the ECM must be calibrated. Refer to Troubleshooting, "Generator Output Power Sensor - Calibration".