New Holland ENG 3910 – Engine Control Unit (ECU): Fuel metering unit: Error check for loose contact between metering unit and ECU

The Engine Control Unit (ECU) has detected an intermittent open circuit or loose connection in the wiring harness that controls the Fuel Metering Unit (MeUn / MPROP valve). A loose contact here can lead to severe fuel pressure oscillations, erratic engine behavior, or stalling.

• T6
• T7
• T8
• T9
• L-Series
• L220
• W50C
• W60C
• W70C
• W80C
• CR
• CX Elevation

1. 1

   Connect the Electronic Service Tool (EST) to verify that fault code 3910 is currently active.

2. 2

   Remove the electrical connector at the Fuel Metering Unit (located on the high-pressure fuel pump) and the corresponding connector at the Engine ECU.

3. 3

   Inspect all connector pins to ensure they are not bent, pushed back into the housing, or corroded.

4. 4

   Trace the wiring harness between the fuel metering unit and the ECU. Look for chafing, pinch points, or heat damage that could cause an intermittent open circuit.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent electrical shorts while working on the ECU wiring.

2. 2

   Repair Wiring/Connectors

   If the diagnostic checks reveal damaged wiring, splice and repair the harness using weather-sealed connectors. If the connector pins are corroded, clean them with electrical contact cleaner. If the connector's locking tab is broken (a common cause of "loose contact" vibrations), replace the pigtail connector.

3. 3

   Secure Connections

   Reconnect the harness to the Fuel Metering Unit and the ECU, ensuring the connectors click firmly into place and are locked.

4. 4

   Component Replacement (If Necessary)

   If the wiring and connectors test perfectly but the code persists, the internal solenoid coil of the Fuel Metering Unit itself may be failing intermittently. In this case, remove the mounting screws holding the metering unit to the high-pressure pump and install a new unit.

5. 5

   Clear Codes and Test

   Reconnect the battery, use the diagnostic service tool to clear the fault codes, and run the engine to verify that fuel pressure is stable and the code does not return.