Case IH F-519744-15 - ECU – Engine Control Unit (ECU / ECM): Fuel rail pressure has exceeded maximum negative deviation limits

The Engine Control Unit (ECU) has commanded the Fuel Metering Unit (MeUn) to a 0-delivery state (100% Pulse Width Modulation), expecting the fuel rail pressure to drop. However, the pressure in the common rail remains too high. This indicates that fuel is either still entering the high-pressure rail (due to a stuck open metering unit or electrical short) or the fuel is unable to return to the tank (due to a clogged return line).

• MAGNUM AFS Connect
• 240 Series Axial-Flow Combines
• Magnum Series (MX210, MX230, MX255, MX285)
• Farmall Series (40, 45, 50)
• Austoft 9900 Sugarcane Harvesters

1. 1

   Check for accompanying codes, specifically code 3106 (DTC 1145) indicating the Fuel pressure relief valve reached maximum allowed opening count. Resolve these first.

2. 2

   Verify the tractor's battery power supply has not been connected to an external power supply, which can cause voltage irregularities. Disconnect and retest if applicable.

3. 3

   Inspect the low-pressure fuel tubes to ensure the return line from the high-pressure pump to the fuel tank is free and not clogged.

4. 4

   Test the Metering Unit (MeUn) to check if it is physically closing when commanded to 100% PWM. A unit stuck in the open position will cause this fault.

5. 5

   Inspect the electrical wiring harness to the Fuel Metering Unit for shorts to ground or open circuits.

1. 1

   Clear low-pressure return lines

   If diagnostic checks reveal a clogged low-pressure return line, clear the blockage or replace the collapsed/clogged fuel line to allow fuel to return to the tank.

2. 2

   Replace Fuel Metering Unit

   If the return lines are clear but the metering unit is stuck open or failing electrically, replace the Fuel Metering Unit (FCA) on the high-pressure fuel pump.

3. 3

   Replace Pressure Relief Valve (PRV)

   If the rail pressure spiked high enough to trigger the PRV, or if code 3106 (DTC 1145) is present, the PRV has likely been compromised and must be replaced.

4. 4

   Reset PRV counter

   If the PRV is replaced, you must use the Case IH Electronic Service Tool (EST) to perform a PRV counter reset.

5. 5

   Clear codes and test operation

   Clear all inactive fault codes using the EST and run the engine to verify that rail pressure responds correctly to ECU commands without exceeding deviation limits.