Massey Ferguson 520307.31 – Engine ECU: Fuel Rail Pressure High

The engine's control system has detected that the fuel pressure inside the common rail has exceeded the maximum measurable limit or maximum safe offset. This triggers an over-pressure protection mode, resulting in forced power degradation, torque limitation, or a forced engine shutdown to protect the injectors and high-pressure fuel lines.

• 4710
• 7724S
• 5712SL
• 7722S
• 7722
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 4708
• 7726S
• 4707
• 4709
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 5710 SL
• 5711 SL
• 5712 SL
• 5713 SL
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• 2604H
• 2605H
• 2606H
• 2607H
• 2635

1. 1

   Safety Warning: High-pressure diesel fuel can penetrate the skin and cause severe or fatal injuries. Never loosen fittings while the engine is running or immediately after shutdown. Wait for the pressure to bleed off.

2. 2

   Diagnostic Tool Monitoring: Connect the AGCO EDT (Electronic Diagnostic Tool) or WinEEM4 software. Monitor the real-time fuel rail pressure. If the sensor reads maximum pressure (e.g., 200 MPa) while the engine is off, the sensor is internally shorted.

3. 3

   Sensor Voltage Test: The rail pressure sensor operates on a 5 Vdc reference supply from the ECU. Back-probe the sensor: at 0 MPa (engine off, pressure relieved), the output voltage should be approximately 0.5V. If it outputs ~4.5V constantly, the sensor or wiring is faulty.

4. 4

   Wiring Harness Inspection: Check the wiring harness between the Engine ECU and the rail pressure sensor for a short circuit to power, which will cause a falsely high reading.

5. 5

   Fuel Return Line Check: Inspect the fuel return (overflow) lines from the common rail and injectors back to the fuel tank. A physical blockage or kink in the return line prevents excess fuel from escaping, causing actual rail pressure to spike.

6. 6

   Pressure Limiting Valve (PRV) Check: Verify if this valve has failed closed or if the high-pressure pump regulator is stuck open.

1. 1

   Disconnect Power

   Disconnect the negative (-) battery cable to prevent accidental electrical shorts and to disable the electric fuel feed pump.

2. 2

   Clean the Area

   Thoroughly clean the area around the common rail and the fuel pressure sensor to prevent dirt from contaminating the high-pressure fuel system.

3. 3

   Remove the Sensor

   Disconnect the electrical connector from the fuel rail pressure sensor. Carefully unscrew the sensor from the common rail. Have a shop rag ready to catch residual diesel fuel.

4. 4

   Install New Components

   Thread the new fuel rail pressure sensor into the common rail and tighten it to the manufacturer's specified torque. Reconnect the electrical harness. (Note: If the PRV was found to be the mechanical cause of the over-pressure, replace it as well. PRV tightening torque is typically 100 Nm).

5. 5

   Bleed the Fuel System

   Open the bleeding plug on the pre-filter bracket. Attach a transparent hose to the plug hole and route it into a container. Pump the hand pump on top of the pre-filter bracket until fuel flows without any air bubbles. Close the bleeding plug.

6. 6

   Clear Codes

   Reconnect the negative battery cable. Use the AGCO diagnostic tool to clear the 520307.31 fault code.

7. 7

   Test Run

   Start the engine and monitor the live fuel rail pressure data to ensure it stays within normal operating parameters.