New Holland 3171 – EDC: Fuel Rail System Pressure Too Low

The pressure in the common rail fuel system has dropped below the minimum required level for proper engine operation. This condition can lead to a range of engine performance issues, including loss of power, rough running, difficulty starting, or complete engine shutdown. In some instances, the engine may enter a "limp mode" to prevent damage. The fault is a critical warning that points to a problem in either the low-pressure or high-pressure side of the fuel delivery system.

• T4
• T5
• T6000
• T8000
• T9000
• TG
• TS110A
• TS125A
• TS135A
• TL-A
• Farmall
• B100B
• B110B
• B115B
• Axial-Flow
• Patriot
• TK4
• T5000

1. 1

   Verify Active Fault: Turn the ignition to the 'RUN' position and use a diagnostic tool to check if the fault code 3171 is currently active. Note down all fault codes, the number of occurrences, and the engine hours of the last occurrence before clearing them.

2. 2

   Check Fuel Quality and Level: Ensure the fuel tank is not empty and inspect the fuel for contaminants such as water, dirt, or algae.

3. 3

   Inspect Fuel Filters: Check the primary and secondary fuel filters for clogging or discoloration. Look for water in the fuel-water separator bowl.

4. 4

   Bleed the Fuel System: If air is suspected in the fuel lines, which can cause sputtering or failure to start, bleed the system according to the procedure in the operator's manual.

5. 5

   Inspect for Leaks: Carefully inspect the low-pressure fuel lines for any signs of leaks, which could introduce air into the system. Also, check the high-pressure side, including injector lines and the pressure relief valve, for any visible leaks.

6. 6

   Listen for Fuel Pump Operation: When the key is turned, listen for the sound of the electric lift pump to ensure it is running.

1. 1

   Clear Fault Codes and Re-evaluate

   After noting all active faults, clear the codes and operate the machine to see if fault 3171 returns. If it does not, the issue may have been intermittent. If it does, proceed to the next step.

2. 2

   Test the Rail Pressure Sensor

   Disconnect the electrical connector from the rail pressure sensor. With the ignition off, use a multimeter to measure the resistance between pins 1 and 2 on the sensor itself. A reading of approximately 45k Ω is expected. If the reading is incorrect, the sensor is likely faulty and should be replaced.

3. 3

   Check Wiring and Connections

   Inspect the pins on the rail pressure sensor connector and the corresponding connector on the engine controller (Connector C or EDC7) for damage, corrosion, or pins that are not fully seated. With both connectors disconnected, check for continuity in the wiring harness between the sensor connector and the engine controller connector. Specifically, check the circuit from pin 1 of the sensor connector to pin 12 of Connector C, and from pin 2 of the sensor connector to pin 14 of Connector C. Repair any open or shorted wires.

4. 4

   Measure Fuel Pump Pressure

   If the sensor and wiring are confirmed to be good, the issue may lie with the fuel pumps. Use a pressure gauge to test the output of the low-pressure lift pump to ensure it is delivering adequate pressure to the high-pressure pump. If low-pressure supply is adequate, further diagnostics on the high-pressure pump may be necessary. This can include checking the pump's output under load and measuring the fuel return volume from the injectors, as excessive return can indicate internal leakage.

5. 5

   Replace Components

   Based on the diagnostic findings, replace the faulty component, which could be the fuel filters, rail pressure sensor, or a fuel pump. After replacement, clear the fault codes and run the machine to confirm the repair has resolved the issue.