Case IH F-5571-10 - ECU – Engine Control Unit (ECU): Fuel pressure relief valve is forced to open, perform pressure shock

Fuel pressure within the high-pressure common rail exceeded safe operating parameters, forcing the mechanical Pressure Relief Valve (PRV) to pop open to protect the fuel system from catastrophic over-pressure damage.

• MAGNUM AFS Connect
• 240 Series Combines
• Austoft 9900 Sugarcane Harvesters
• Magnum series tractors
• Maxxum series tractors
• Farmall series tractors

1. 1

   Check the Rail Pressure Sensor and its wiring harness connections for shorts, high resistance, or intermittent signals that could cause the ECU to command maximum fuel pressure.

2. 2

   Check the Fuel Metering Unit (M-PROP) on the high-pressure pump and its wiring harness for sticking or electrical faults causing runaway rail pressure.

3. 3

   Check the Pressure Relief Valve (PRV) for tightness and verify its opening pressure to determine if the valve has weakened over time and is opening prematurely.

4. 4

   Check for general rail system failures, looking for blockages or return line restrictions that could artificially inflate rail pressure.

1. 1

   Perform a Pressure Shock

   Initiate the automated diagnostic routine via the Case IH Electronic Service Tool (EST) to spike the rail pressure and attempt to reseat the mechanical relief valve and clear the fault state.

2. 2

   Evaluate the Valve

   If the pressure shock successfully reseats the valve and rail pressure normalizes, clear the code and test run the machine. If the code immediately returns or the valve fails to hold pressure, the PRV is permanently compromised and must be replaced.

3. 3

   Replace the PRV (if necessary)

   Thoroughly clean the fuel rail area before removal, as microscopic contamination can destroy common rail components. Remove the faulty pressure relief valve from the fuel rail, install the new valve, and torque to OEM specifications.

4. 4

   Address Root Causes

   If the PRV was forced open by a genuine over-pressure event (rather than a weak valve spring), replace the faulty Rail Pressure Sensor or Fuel Metering Unit identified during the diagnostic checks.

5. 5

   Clear Codes

   Use the diagnostic tool to clear the F-5571-10 code and verify normal operation under load.