New Holland ENG 3305 – Engine Control Unit (ECU) / Electronic Diesel Control (EDC): Fuel Metering Unit: Minimum Common Rail Pressure Exceeded

This fault indicates a low fuel pressure condition. The engine control system detects that the actual fuel pressure in the common rail has dropped below the minimum acceptable threshold compared to the target pressure commanded by the ECU. The Fuel Metering Unit (also known as the M-PROP or ZME valve) is commanded to increase fuel volume to the high-pressure pump, but the system is unable to achieve or maintain the required rail pressure.

• L220
• L225
• L230
• SR175
• T5
• T7
• T8
• T9
• W190B

1. 1

   Verify there is adequate fuel in the tank and inspect/replace the primary and secondary fuel filters (including the water separator).

2. 2

   Test the low-pressure lift pump to ensure it is delivering adequate fuel pressure (typically around 5.0 bar) to the inlet of the high-pressure pump.

3. 3

   Inspect the wiring harness and connector to the Fuel Metering Unit for loose contacts, corrosion, or short circuits. Measure the electrical resistance of the coil (expected: 2.6 to 3.15 Ω at 20°C).

4. 4

   Check the mechanical Pressure Relief Valve (PRV) on the fuel rail. Disconnect the return pipe; if fuel flows out during cranking or running, the valve is stuck open.

5. 5

   Perform an injector shut-off/leak-off test to ensure an injector is not stuck open and returning excessive fuel to the tank.

1. 1

   Prepare machine

   Park the machine on a level surface, turn the key OFF, and disconnect the battery.

2. 2

   Clean pump area

   Thoroughly clean the exterior of the high-pressure fuel pump (Bosch CP3) and the surrounding area to prevent dirt from entering the fuel system.

3. 3

   Disconnect harness

   Disconnect the electrical harness connector from the Fuel Metering Unit.

4. 4

   Remove mounting screws

   Remove the mounting screws securing the unit to the high-pressure pump body.

5. 5

   Remove unit

   Carefully pull the Fuel Metering Unit out of the pump housing.

6. 6

   Lubricate O-rings

   Lubricate the O-rings on the new Fuel Metering Unit with clean diesel fuel.

7. 7

   Install new unit

   Insert the new unit into the pump and tighten the mounting screws to the OEM torque specification.

8. 8

   Reconnect harness

   Reconnect the electrical harness.

9. 9

   Prime fuel system

   Reconnect the battery and prime the fuel system to purge any trapped air.

10. 10

    Clear codes and verify

    Start the engine and use the CNH Electronic Service Tool (EST) to clear the fault code and verify that the actual rail pressure now matches the target pressure at idle and under load.