Case IH 3106 (F-5571-15) - ECU – Engine Control Unit (ECU): Fuel pressure relief valve reached maximum allowed opening count.

In common rail diesel systems, a mechanical Pressure Relief Valve (PRV) is integrated into the high-pressure fuel rail. It acts as a safety mechanism, opening to bleed off fuel if excessive rail pressure occurs. The Engine Control Unit (ECU) monitors sudden drops in rail pressure that indicate the PRV has popped open. If the ECU counts that the PRV has opened 50 times, it triggers this fault code. Once the valve has opened this many times, its internal spring is weakened, and it will no longer hold the correct rail pressure.

• VESTRUM CVX
• Puma Series Tractors
• 240 Series Axial-Flow Combines
• Farmall 40, 45, and 50 Tractors
• 9900 Sugar Cane Harvesters

1. 1

   Check for Air Ingress / Inlet Restrictions: Use a test line constructed with clear tubing at the inlet of the high-pressure pump to observe for air bubbles in the system while running.

2. 2

   Test Low-Pressure Supply: Verify that the vacuum between the inlet of the low-pressure pump and the fuel tank does not exceed 127 mm (5 inches) of Hg.

3. 3

   Test High-Pressure Supply: Fuel supply pressures between the fuel filter and the inlet to the high-pressure pump should be a minimum of 5 bar (72 psi) with the engine loaded or unloaded.

4. 4

   Check Related Faults: Look for active codes related to the Fuel Metering Unit (e.g., 3107, 3108) or the Rail Pressure Sensor (e.g., 3110, 3111, 3112), as a failure in these components is usually what causes the rail pressure to spike and blow the relief valve.

1. 1

   Preparation

   Clean the entire fuel rail and surrounding area thoroughly. Extreme cleanliness is required, as microscopic contamination can destroy common rail components.

2. 2

   Relieve Pressure

   Ensure the engine is off and the high-pressure fuel system has completely depressurized before opening any lines.

3. 3

   Remove the PRV

   Disconnect the return line from the Pressure Relief Valve on the fuel rail, then unthread the old valve from the rail.

4. 4

   Install the New PRV

   Thread the new pressure relief valve into the fuel rail and torque to OEM specifications. Reattach the return line.

5. 5

   Prime the System

   Always use fresh, filtered fuel when priming the system. It is highly recommended to replace the fuel filters at this time.

6. 6

   Reset the ECU Counter

   Using a diagnostic tool (such as the Case IH EST or Bosch ESI[truck]), clear the fault codes and perform the "Fuel Pressure Relief Valve Maintenance" reset to clear the ECU's opening counter back to zero.

7. 7

   Test Run

   Start the engine and apply a load (e.g., using hydraulics over relief or a dynamometer). Monitor the actual rail pressure versus the commanded rail pressure to ensure the system stabilizes and the new valve does not pop.