Case IH 3108 – Engine Controller (Engine ECU / ECM): Engine Controller High Pressure Pump Metering Unit Circuit - Short Circuit To Ground

The Engine Control Module (ECM) has detected a short circuit to ground on the circuit controlling the high-pressure fuel pump metering unit (also known as the Fuel Metering Unit or MPROP), or on 'Main Relay 1' which provides its power supply. This condition prevents the engine controller from properly regulating the amount of fuel entering the high-pressure pump, leading to engine malfunction, derating, or a no-start condition.

• Farmall
• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Magnum Series Tractors
• Steiger Series Tractors

1. 1

   Test Main Relay 1 (power supply relay for the high-pressure pump metering unit) for internal shorts or a stuck relay

2. 2

   Inspect the wiring harness running from the Engine Controller to the High-Pressure Pump Metering Unit for chafed insulation, pinched wires, or rubbing against the engine block or chassis

3. 3

   Disconnect the metering unit and the ECM to check connector pins for corrosion, moisture, or damage, and test signal and power wires for continuity to ground

4. 4

   Perform a resistance test on the metering unit solenoid to ensure the internal coil has not shorted to its own casing

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Replace Relay

   If Main Relay 1 failed the diagnostic check, replace the relay and clear the codes to see if the fault returns.

3. 3

   Repair Wiring

   If a short to ground is found in the harness, repair the damaged section of wiring using OEM-approved heat-shrink connectors, or replace the affected harness section. Route the harness away from high-heat or high-vibration areas.

4. 4

   Replace Metering Unit

   If the wiring and relay are intact but the metering unit solenoid is internally shorted, remove the mounting bolts securing the metering unit to the high-pressure fuel pump and install a new unit. Torque mounting bolts to OEM specifications (e.g., 8.0 N·m / 5.9 lb-ft for standard F-series engine fuel components).

5. 5

   Clear Codes and Test

   Reconnect the battery, use an electronic service tool (EST) to clear the inactive 3108 fault code, and run the engine to verify the repair.