New Holland ENG 3114 – Engine Control Module (ECM): Main Relay 1 (High Pressure Pump - power supply to the fuel metering unit) Short to Ground

The engine controller has detected that the electrical circuit supplying power (via Main Relay 1) to the fuel metering unit (also known as the MPROP, FCA, or fuel measurement solenoid valve) on the high-pressure fuel pump has shorted to ground. This prevents the fuel metering unit from properly regulating the fuel volume entering the high-pressure pump, which will cause engine derating, loss of power, or a no-start condition.

• T7.220
• T7.235
• T7.250
• T7.260
• T7.270
• T8 Series
• T6 Series (T6010 through T6070)
• Magnum 235-340 Series 4

1. 1

   Locate Main Relay 1 in the fuse/relay center and swap it with a known good relay of the same type to check if the short is internal to the relay.

2. 2

   Trace the wiring harness from Main Relay 1 and the ECM down to the fuel metering unit on the high-pressure fuel pump. Inspect for chafed insulation, melted wires, or pinch points touching the engine block or chassis.

3. 3

   Disconnect the electrical connector at the fuel metering unit and use a multimeter to check for continuity to ground on the power supply pin. If the short remains, the wiring harness is faulty. If the short disappears, the fuel metering unit has failed internally.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Address the Relay

   If diagnostic checks pointed to a faulty relay, replace Main Relay 1.

3. 3

   Repair Wiring

   If a short was found in the harness, open the wire loom, cut out the damaged section of the power supply wire, and solder/heat-shrink a new section of wire. Re-loom and secure the harness away from vibration points.

4. 4

   Replace the Fuel Metering Unit

   If internally shorted, clean the area around the Bosch CP3 high-pressure fuel pump thoroughly to prevent dirt from entering the fuel system. Remove the mounting screws holding the fuel metering unit to the pump. Carefully extract the unit (be mindful of the O-rings). Lubricate the O-rings on the new fuel metering unit with clean diesel fuel and install it into the pump. Torque the fasteners to OEM specifications.

5. 5

   Reassemble and Clear Codes

   Reconnect the electrical connector and the battery. Turn the key on, clear the inactive fault codes via the diagnostic menu or service tool, and start the engine to verify the repair.