Case IH 3305 (F-519745-17) - ECU – Engine Control Unit (ECU): Fuel rail pressure has dropped below the minimum limit in controlled mode.

The engine's control system has detected that the actual fuel pressure in the common rail is lower than the target pressure requested by the system. This typically points to fuel starvation, a restriction in the low-pressure supply, a failing high-pressure pump component, or a faulty pressure sensor.

• VESTRUM CVX
• Magnum Tractors 235, 250, 280, 310, 340, 380 (Series 4)
• Steiger Tractors
• Puma Tractors 165, 180, 195, 210, 225 CVX
• Farmall Tractors 115U
• 721F Wheel Loaders
• 821F Wheel Loaders
• 921F Wheel Loaders
• Skid Steers / CTLs

1. 1

   Verify Fuel Level: Ensure the tank is not empty or critically low, which can introduce air into the system.

2. 2

   Check Low-Pressure Vacuum: Measure the vacuum between the inlet of the low-pressure pump and the fuel tank. It should not exceed 127 mm (5 inches) of Hg. High vacuum indicates a clogged tank vent, collapsed line, or blocked suction tube.

3. 3

   Check Low-Pressure Supply: Measure the fuel supply pressure between the fuel filter and the inlet to the high-pressure pump. It must be a minimum of 5 bar (72 psi) with the engine loaded or unloaded.

4. 4

   Inspect Fuel Filters: Check the primary and secondary fuel filters for severe clogging, gelling, or water contamination.

5. 5

   Test the Fuel Rail Pressure Sensor: Verify that the sensor is outputting plausible voltage signals to the ECU and is not shorted or skewed.

6. 6

   Inspect for Leaks: Check the high-pressure fuel lines, injector tubes, and the pressure relief valve for bypass leaks.

1. 1

   Resolve Supply Restrictions

   If the low-pressure supply is below 5 bar (72 psi), replace the primary and secondary fuel filters. Bleed the fuel system completely to remove any trapped air.

2. 2

   Test Run

   Clear the fault codes and run the machine under load. If code 3305 does not return, the issue was a restricted filter.

3. 3

   Replace the Fuel Metering Unit (SCV)

   If the low-pressure supply is adequate but the rail pressure still drops below the target limit, the Fuel Metering Unit (also known as the Suction Control Valve or MeUn) on the high-pressure pump is likely sticking or failing to command enough fuel flow. Remove and replace the metering unit.

4. 4

   Replace the Fuel Rail Pressure Sensor

   If diagnostic tests show the sensor's electrical signal is erratic or implausible (often accompanied by codes 3306 or 3310), depressurize the fuel system and replace the fuel rail pressure sensor.

5. 5

   Final Verification

   Clear all ECU fault codes using a diagnostic tool. Perform a test drive under heavy load to ensure the actual rail pressure matches the desired rail pressure without dropping below the minimum threshold.