Case IH 3910 – Engine Control Unit (ECU): Fuel metering unit intermittent electrical connection failure

The Engine Control Unit detects an open circuit, high resistance, or an intermittent drop in voltage communicating with the fuel metering unit (an electronic PWM controlled solenoid located at the inlet of the high-pressure fuel pump).

• skid steer
• Skid Steer Loaders (SR175, SV250, TR320)
• Compact Track Loaders
• 240 Series Axial-Flow Combines
• Puma series tractors
• Steiger series tractors
• Farmall series (40-45-50 with CVT)
• Sugar Cane Harvesters (A8000, A8800)

1. 1

   Check for concurrent fault codes (e.g., 3735, 3301, 3911, 3912) using the Electronic Service Tool (EST) and diagnose those first.

2. 2

   Verify that the tractor's battery power supply has not been connected to an external power supply (like a booster); disconnect if applicable and test.

3. 3

   Inspect the wiring harness between the ECU and the fuel metering unit for chafing, breaks, or heat damage.

4. 4

   Disconnect the harness at the metering unit and the ECU to check for bent, pushed-back, or corroded pins.

1. 1

   Turn the starter switch to the "OFF" position and disconnect the battery to prevent electrical spikes.

2. 2

   Locate the Fuel Metering Unit, which is mounted directly to the inlet of the high-pressure fuel pump (typically a Bosch CP3 or CP4 pump).

3. 3

   Disconnect the electrical connector at the metering unit. Clean the contacts thoroughly with electrical contact cleaner and ensure the weather seal is intact.

4. 4

   Perform a continuity test on the two wires running from the metering unit connector back to the Engine ECU.

   If resistance is high or continuity drops when wiggling the harness, repair or replace the damaged section of the wiring harness.

5. 5

   If the wiring harness and connectors test perfectly, the internal solenoid of the Fuel Metering Unit has likely failed. Remove the mounting bolts for the metering unit and extract it from the high-pressure pump.

6. 6

   Lubricate the O-rings on the new Fuel Metering Unit with clean diesel fuel and install it into the pump. Torque the mounting bolts to OEM specifications.

7. 7

   Reconnect the battery, turn the key to the "ON" position, and use the EST to clear the fault codes. Start the engine and verify that code 3910 does not return.