New Holland ENG 329 – Engine Controller (ECM / Engine ECU): CAPS Pump has an overpumping failure.

Triggers when the engine control module detects that the fuel pressure in the injection pump is not changing in accordance with operating conditions (speed and power demands), or it detects an internal overpumping condition. It is often accompanied by engine surging, loss of power, or stalling.

• TG255
• TG285
• TJ275
• TJ325
• MX240
• MX255
• MX270
• MX285
• STX275
• STX325

1. 1

   Check for aerated fuel or air leaks by inspecting the fuel lift pump and ensuring mounting bolts are tight.

2. 2

   Inspect fuel supply hoses from the tank for kinks or collapsing under vacuum.

3. 3

   Check tank venting by loosening the fuel cap when running rough; a rush of air indicates a vacuum pulling on the tank.

4. 4

   Inspect the lift pump intake screen for debris and replace all primary and secondary fuel filters.

5. 5

   Verify ECM software is updated to the latest revision to prevent false pump codes.

1. 1

   Preparation

   Disconnect the battery. Thoroughly clean the engine area around the CAPS pump to prevent dirt from entering the open fuel lines.

2. 2

   Removal

   Disconnect the fuel supply and return lines. Disconnect all electrical connectors to the pump, paying special attention to the Transient Suppressor pigtail.

3. 3

   Dismount

   Remove the mounting hardware and carefully extract the heavy CAPS pump from the gear housing.

4. 4

   Transient Suppressor Replacement

   You must replace the Transient Suppressor when installing a new CAPS pump. This component protects the pump's electronics by ensuring a clean signal from the ECM. Reusing an old suppressor can cause premature failure of the new pump.

5. 5

   Installation

   Mount the new/remanufactured CAPS pump. Torque mounting bolts to OEM spec.

6. 6

   Reconnection

   Reattach all fuel lines and plug in the new Transient Suppressor and ECM harnesses.

7. 7

   Bleeding

   Prime and bleed the fuel system to ensure absolutely no air is trapped in the lines before cranking.

8. 8

   Testing

   Reconnect the battery, start the engine, and verify that the ENG 329 code is cleared and the engine no longer surges under load.