New Holland ENG 559 – Engine ECM: Front fueling actuator underfueling

Fuel rail pressure is lower than the pressure commanded by the engine computer (typically a difference of 1450 psi or more below the commanded pressure).

• T8000 series
• TJ Series
• T9 Series
• T9000 Series
• CR9090
• CX8080 Elevation
• CX8090 Elevation
• Magnum series
• Steiger series
• MX/TG series

1. 1

   Verify that you have an unrestricted fuel supply from the tank to the pump (a clogged filter is the most common cause of underfueling).

2. 2

   Check the low-pressure fuel lines for leaks that could allow air to enter the system.

3. 3

   Inspect injector tube seals (on early HPCR engines, injector connector tubes can lose their seal, causing a massive loss of rail pressure).

4. 4

   Inspect the wiring harness and the connector at the fuel pump actuator for chafing, corrosion, or loose pins.

1. 1

   Replace Fuel Filters

   Start by replacing both the primary and secondary fuel filters. Prime the fuel system to ensure all air is bled out. Run the engine to see if the code clears (the engine may need to idle for about a minute for the active fault to transition to inactive).

2. 2

   Re-torque Injector Tubes

   If the filters do not fix the issue, remove the valve cover and re-torque the high-pressure injector connector tubes to factory specifications to eliminate internal pressure leaks.

3. 3

   Replace the Fuel Pump Actuator

   If pressure is still below the commanded threshold: Clean the area around the high-pressure fuel pump to prevent debris from entering the system. Disconnect the electrical connector at the fuel pump actuator (typically features green and yellow control wires). Remove the mounting screws holding the actuator to the fuel pump. Carefully pull the actuator out of the pump housing. Lubricate the O-rings on the new actuator with clean diesel fuel. Insert the new actuator into the pump, install the mounting screws, and torque them to OEM specifications. Reconnect the wiring harness.

4. 4

   Clear Codes

   Cycle the key, start the engine, and allow it to idle to verify that the target rail pressure is met and the ENG 559 code remains inactive.