Case IH 3807 – Engine ECU: Fuel Metering Unit : maximum negative rail pressure deviation with metering unit on lower limit is exceeded (second stage)

This code indicates a severe under-pressure condition in the high-pressure common rail (HPCR) fuel system. The engine is demanding a specific fuel rail pressure, but the actual pressure has dropped too low. In response, the Engine ECU commands the Fuel Metering Unit to its lower limit to maximize fuel flow. Because the system still cannot reach the target pressure even at maximum commanded flow, this second stage fault is triggered.

• Tractors
• Combines
• Windrowers
• Skid Steers

1. 1

   Check low-pressure fuel supply (minimum 5 bar / 72 psi with engine loaded or unloaded).

2. 2

   Check for air in the fuel system by installing a clear tubing test line at the injection pump inlet and observing for bubbles.

3. 3

   Inspect primary and secondary fuel filters for heavy restrictions or clogging.

4. 4

   Test the Fuel Metering Unit (FCA/M-PROP) by unplugging it during a hard start condition to see if the engine starts (defaults to max pressure).

5. 5

   Check the Pressure Relief Valve (PRV) on the fuel rail to see if it has failed or is popping open prematurely.

6. 6

   Check injector return flow for leaking hollow check balls bleeding off rail pressure.

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