Case IH 3808 – Engine Control Unit (ECU) / EDC: High pressure pump fuel delivery quantity at low idle is too high

The engine's control system is detecting that the high-pressure fuel pump is delivering more fuel volume than expected or commanded when the engine is operating at low idle. This is typically caused by a mechanical or electrical issue with the Fuel Metering Unit failing to regulate the fuel volume entering the high-pressure pump.

• Steiger T4B
• 240 Series Axial-Flow Combines (7230, 8230, 9230)
• Magnum series (7110, 310, 335)
• Puma series
• Maxxum series (115)
• Farmall series (75C, 115U)
• Skid Steers / Compact Track Loaders

1. 1

   Inspect primary and secondary fuel filters for clogs or heavy restrictions

2. 2

   Test the low-pressure fuel pump hydraulic circuit using a 0 to 11 Bar (0 to 160 PSI) gauge to verify supply pressure to the high-pressure pump

3. 3

   Inspect the high-pressure fuel lines and common rail for any external leakage

4. 4

   Perform an injector leak-off test to check for tightness and excessive return flow (leak-back)

5. 5

   Inspect the wiring harness and connector to the Fuel Metering Unit (FCA) on the high-pressure pump for shorts, corrosion, or open circuits

1. 1

   Relieve Fuel Pressure

   Ensure the engine is off and the high-pressure fuel system has completely depressurized before opening any lines.

2. 2

   Address Low-Pressure Issues

   If the fuel filters were clogged or the low-pressure lift pump failed the pressure test, replace the filters or the low-pressure pump first, prime the system, and retest.

3. 3

   Replace the Fuel Metering Unit

   Disconnect the electrical connector from the metering unit on the high-pressure pump. Remove the mounting screws and carefully extract the metering unit. Lubricate the O-rings on the new metering unit with clean diesel fuel and install it into the pump. Torque the fasteners to OEM spec.

4. 4

   High-Pressure Pump Replacement

   If replacing the metering unit does not resolve the issue, the high-pressure pump assembly itself has likely suffered internal wear (low efficiency) and must be replaced entirely.

5. 5

   Clear Codes and Relearn

   Use a diagnostic service tool to clear the 3808 (3C65) fault code. If the EDC or major fuel components were replaced, follow the appropriate service tool procedure to restore self-learning parameters. Run the engine at low idle to verify the code does not return.