Case IH 3804 – Engine Control Unit (ECU): Fuel Metering Unit : Threshold of the battery under voltage for switching to start with MeUn procedure

During the engine cranking/starting procedure, the system voltage dropped below the minimum threshold required to properly operate the Fuel Metering Unit (MeUn). If the battery voltage drops too low while the starter is engaged, the ECU cannot accurately control the valve to regulate fuel pressure.

• Case IH and New Holland agricultural equipment equipped with FPT Tier 3 and Tier 4a engines
• NEF engine series

1. 1

   Battery Load Test: Test the batteries to ensure they have sufficient cold cranking amps (CCA) and are not dropping below ~9.5V - 10V during cranking.

2. 2

   Voltage Drop Test: Monitor the voltage directly at the ECU power supply pins and the Fuel Metering Unit connector while cranking the engine.

3. 3

   Inspect Cables and Grounds: Check the battery terminals, crossover cables, and main chassis/engine block grounds for corrosion, looseness, or fraying.

4. 4

   Starter Motor Draw Test: A failing starter motor can draw excessive amperage, dragging the entire system voltage down below the ECU's operating threshold.

5. 5

   Wiring Harness Inspection: Inspect the wiring harness between the ECU and the Fuel Metering Unit for chafing or poor pin fitment that could cause high resistance.

1. 1

   Disconnect Power

   Disconnect the negative battery cables.

2. 2

   Clean Connections

   Remove, clean, and tighten all battery terminals and main ground connections to the chassis and engine block.

3. 3

   Replace Battery/Starter

   If the battery failed the load test, replace it. If the starter motor is drawing excessive current and causing the voltage drop, replace the starter.

4. 4

   Repair Wiring

   Repair any damaged wiring or replace corroded connectors in the ECU power supply or Fuel Metering Unit circuit.

5. 5

   Replace Fuel Metering Unit

   If the electrical supply system (batteries, starter, cables) is verified to be in perfect condition, the solenoid coil inside the Fuel Metering Unit may be internally shorting and causing a localized voltage drop. In this case, replace the Fuel Metering Unit on the high-pressure fuel pump.

6. 6

   Clear Codes

   Use the CNH Electronic Service Tool (EST) to clear the inactive fault codes. Crank the engine to verify the code does not return.