Massey Ferguson 157.2 – Engine Control Unit (ECU): Fuel Rail Pressure Is Not As Expected During Startup Or Shutdown

The engine's common rail fuel system is failing to reach or maintain the target fuel pressure commanded by the controller during the engine's startup cranking phase or the shutdown sequence. This typically indicates a loss of pressure (fuel starvation, bypassing relief valve, or worn high-pressure pump) or a skewed reading from a faulty sensor.

• 4710
• 7724S
• 5712SL
• Interim Tier 4 (2012-2015)
• 7722
• 7722S
• 7615
• 5613
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7616
• 7618
• 5608
• 4708
• 7619
• 7626
• 7726S
• 7624
• 4707
• 4709
• 5711SL
• 7614
• 7718S
• 5610
• 7620
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 5612
• 7622
• 7720
• Tier 4 (2015-2021)
• 5611
• 7715S
• 5609
• 7724

1. 1

   Check Fuel Filters: Restricted or clogged fuel filters are the most common cause of pressure drops. Verify the condition of the filter media.

2. 2

   Test the Fuel Rail Pressure Sensor: A skewed sensor reading can trigger this code even if actual mechanical pressure is fine. Check the sensor's KOEO (Key On Engine Off) readings using a diagnostic tool to see if it is reporting an impossible baseline pressure.

3. 3

   Inspect the Fuel Pressure Relief Valve: The relief valve on the common rail prevents over-pressure. If it fails or sticks open, it will bypass fuel back to the tank prematurely, preventing the rail from building adequate pressure during startup.

4. 4

   Evaluate the High-Pressure Fuel Pump: Check for internal wear in the high-pressure pump, which may prevent it from generating sufficient pressure at low cranking RPMs.

1. 1

   Replace Fuel Filters

   Start by replacing the primary and secondary fuel filters. Prime the system with fresh, clean fuel to eliminate restriction or contamination as the root cause.

2. 2

   Relieve System Pressure

   If further repair is needed, ensure the engine is off and the high-pressure fuel system has fully depressurized before opening any lines.

3. 3

   Replace the Pressure Relief Valve (if bypassing)

   If diagnostics point to a loss of pressure at the rail, remove the old pressure relief valve from the common rail. Install the new valve, ensuring extreme cleanliness, as microscopic contamination can destroy common rail components.

4. 4

   Replace the Fuel Rail Pressure Sensor (if skewed)

   If the sensor is reporting incorrectly, disconnect the electrical harness, unthread the sensor from the rail, and install the replacement sensor.

5. 5

   Prime and Test

   Bleed the fuel system of any air. Start the engine and monitor the actual vs. commanded fuel rail pressure via a diagnostic tool during startup and shutdown to verify the code is cleared.