Massey Ferguson 157.21 – Engine ECU: Fuel Rail Pressure Is Not As Expected During Startup Or Shutdown

The engine control system has detected that the fuel rail is failing to achieve or maintain the minimum expected pressure threshold when the engine is cranking to start or cycling down during shutdown (Rail pressure raw value is below minimum offset).

• 4710
• 5713SL
• 5712SL
• 4707
• 5711SL
• 4709
• T4
• 5710SL
• 4708
• T4 (2015-2021)
• 5608-5613
• 5710SL-5713SL
• 6612-6616
• 6712-6718S
• 7614-7626
• 7714-7726S
• 8650-8690
• 8727-8740

1. 1

   Check battery voltage and perform a load test, as low voltage during cranking can cause the ECU to misread sensors or disable power stages

2. 2

   Inspect the high-pressure common rail, injector lines, and fittings for any physical fuel leaks

3. 3

   Check the low-pressure fuel system by ensuring the lift pump is operating correctly and fuel filters are not restricted

4. 4

   Disconnect the fuel rail pressure sensor and inspect the wiring harness and connector for corrosion, backed-out pins, moisture, continuity, or shorts

1. 1

   Secure the Machine

   Turn off the tractor, remove the key, and ensure the battery is fully charged.

2. 2

   Resolve Supply Issues

   If diagnostic checks revealed clogged filters or a failing lift pump, replace the filters and bleed the low-pressure fuel system.

3. 3

   Replace the Sensor

   If no physical leaks are found, supply pressure is adequate, and the wiring is intact, the fuel rail pressure sensor has likely failed internally (reading below the minimum offset).

4. 4

   Depressurize

   Ensure the high-pressure fuel system is completely depressurized before opening any lines.

5. 5

   Swap the Sensor

   Unplug the electrical connector, unthread the old fuel rail pressure sensor from the common rail, and install the new OEM sensor. Torque to the manufacturer's specification.

6. 6

   Bleed the System

   Bleed the fuel system to remove any trapped air introduced during the repair.

7. 7

   Clear Codes

   Connect a diagnostic tool (such as the AGCO WinEEM3/EEM4 Service Tool) to the diagnostic port, clear the active 00157.21 / SPN 157 FMI 21 fault code, and run the engine to verify that rail pressure is now within the expected parameters during startup and shutdown.