New Holland 3139 – ECU: Metering Unit Signal Range Check - Signal Too High

The Engine Control Unit (ECU) has detected a voltage from the fuel metering unit (also known as the Fuel Control Actuator or MPROP) that is above the specified maximum range. This indicates an issue with the signal being sent from the metering unit, most commonly caused by the control circuit being shorted to a power source in the wiring harness, or an internal failure within the metering unit itself. This fault affects the proper operation of the high-pressure fuel system and can lead to hard starting, no-start conditions, engine surging, or reduced power.

• T7000 series
• T7030
• T7040
• T7050
• T7060
• T8 series
• T8.xxx

1. 1

   Visually inspect the wiring harness and electrical connector at the fuel metering unit on the high-pressure pump for chafed or melted wires, corrosion in the connector pins, or a loose connection.

2. 2

   Ensure the battery is fully charged and that all main power and ground connections to the chassis and ECU are clean and tight to rule out unstable voltage.

3. 3

   With the key on, check for a constant 12-volt supply at the appropriate pin on the metering unit's electrical connector.

4. 4

   Disconnect the harness from the fuel metering unit solenoid and measure the resistance across the two pins of the unit itself. Normal resistance is approximately 2.6 to 3.2 Ohms; an open circuit (infinite resistance) or out-of-range reading indicates a faulty solenoid coil.

5. 5

   Use a diagnostic tool (like New Holland EST) to monitor desired versus actual fuel rail pressure. Observe the metering unit command signal (often as a percentage or duty cycle) to verify if the feedback voltage is stuck at a maximum value.

1. 1

   Safety First

   Release any residual pressure from the fuel system. Disconnect the negative battery terminal to prevent accidental short circuits.

2. 2

   Clean the Area

   Thoroughly clean the area around the high-pressure pump and the fuel metering unit to prevent contaminants from entering the fuel system.

3. 3

   Disconnect

   Unplug the electrical connector from the metering unit.

4. 4

   Remove the Old Unit

   Carefully remove the two or three mounting bolts and gently extract the unit from the high-pressure pump. Be prepared for a small amount of fuel spillage.

5. 5

   Install the New Unit

   Ensure the mounting surface on the pump is clean. Lightly lubricate the O-rings on the new metering unit with clean diesel fuel or a suitable assembly lubricant. Carefully insert the new unit and tighten the mounting bolts to the manufacturer's specified torque.

6. 6

   Reconnect

   Reattach the electrical connector and the negative battery terminal.

7. 7

   Bleed the Fuel System

   If the system requires it, bleed any air that may have entered the low-pressure side of the fuel system according to the machine's operator manual.

8. 8

   Clear Codes and Test

   Use a diagnostic tool to clear the 3139 fault code. Start the engine and let it run, checking for any fuel leaks. Monitor the fuel rail pressure with the diagnostic tool to ensure it is now regulating correctly.