Massey Ferguson 520336.31 – Engine Control Unit (ECU): Fuel Rail Pressure High. Engine Safety Shutdown Active.

This code indicates that the fuel pressure within the common rail has exceeded the maximum safe operating limit. To prevent catastrophic failure of the high-pressure fuel system components (such as the injectors, fuel rail, or high-pressure lines) and to prevent severe engine damage, the system triggers a forced safety shutdown of the engine.

• 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
• MF 5700 series
• MF 7700 series

1. 1

   Connect a diagnostic service tool and monitor live fuel rail pressure with the engine off. If the pressure reads extremely high while the engine is off, this indicates the Rail Pressure Sensor or its wiring is faulty.

2. 2

   Inspect the wiring harness and connectors for the Fuel Rail Pressure Sensor and the Fuel Metering Valve (Suction Control Valve) on the high-pressure pump. Look for shorts to voltage or ground, which can cause false sensor readings or force the metering valve wide open.

3. 3

   Check the fuel return lines from the fuel rail and the high-pressure pump back to the fuel tank. Kinks, blockages, or restrictions in the return lines can cause fuel pressure to spike rapidly.

4. 4

   If the wiring and return lines are clear, the issue is likely mechanical. Check for a stuck-open Fuel Metering Valve (SCV) on the high-pressure pump (which over-pressurizes the rail) or a failed Pressure Relief Valve (PRV) on the rail (which fails to vent excess pressure).

1. 1

   Depressurize and Prep

   Disconnect the negative (-) battery cable. Thoroughly clean the area around the high-pressure fuel pump and the fuel rail to prevent any dirt or debris from entering the open fuel system.

2. 2

   Replace the Faulty Component

   If the Rail Pressure Sensor is faulty: Disconnect the electrical connector, unscrew the sensor from the rail, and install the new sensor. Torque to OEM specifications. If the Fuel Metering Valve (SCV) is sticking: Locate the valve on the low-pressure side of the high-pressure pump. Disconnect the electrical connector, remove the mounting fasteners, and carefully extract the valve. Lubricate the O-rings on the new valve with clean diesel fuel and install it. If the Pressure Relief Valve is faulty: Remove the return line from the valve on the fuel rail, unscrew the valve, and install the replacement.

3. 3

   Reassemble and Bleed

   Reconnect the battery. Bleed the low-pressure fuel system using the hand primer pump located on the pre-filter bracket until resistance is felt.

4. 4

   Clear and Test

   Connect the diagnostic tool, clear the 520336.31 fault code, and start the engine. Monitor the live rail pressure to ensure it tracks the ECU's requested target pressure without spiking.