Case IH 19718 – Engine Control Module (ECM) / EDC: Maximum negative rail pressure deviation with metering unit on lower limit is exceeded (second stage)

Actual fuel rail pressure is significantly higher than the desired target pressure. The ECM commands the fuel metering unit to its absolute lower limit to bring pressure down, but pressure remains excessively high.

• Tier 4b
• Magnum 235
• Magnum 275
• Magnum 340
• Steiger Series
• Quadtrac Series
• Puma Series
• Optum Series
• 580 Super N Loader
• 621C Loader

1. 1

   Inspect the wiring harness and connectors for the fuel metering unit and the fuel rail pressure sensor for a short to ground, short to battery, or open circuit.

2. 2

   Check the low-pressure side of the fuel system. Ensure the pressure before the gear pump is not excessively high (check the pressure relief valve) and verify that fuel return lines to the tank are not restricted, kinked, or clogged.

3. 3

   Use an Electronic Service Tool (EST) to monitor the actual vs. desired rail pressure. If the pressure reads extremely high even when the engine is off, the rail pressure sensor is likely skewed or shorted.

1. 1

   Connect Diagnostic Tool

   Connect the Case IH Electronic Service Tool (EST) to read all active and stored engine (EDC) faults. Look for accompanying electrical faults (e.g., 3108 Metering Unit Short Circuit) which will pinpoint a wiring issue.

2. 2

   Test the Metering Unit

   If no wiring faults are present, the metering unit is likely mechanically stuck open. Remove and replace the fuel metering unit (M-PROP) on the high-pressure pump.

3. 3

   Test the Rail Pressure Sensor

   If replacing the metering unit does not resolve the overpressure condition, test the voltage at the rail pressure sensor. If the sensor is outputting a voltage that correlates to a high pressure when actual mechanical pressure is normal, replace the fuel rail pressure sensor.

4. 4

   Clear and Verify

   Use the EST to clear the fault codes from the ECM memory. Run the engine and monitor the rail pressure setpoint versus the actual rail pressure to ensure they match and the deviation is resolved.

5. 5

   ECM Replacement (Last Resort)

   If all wiring, the metering unit, and the pressure sensor test perfectly but the fault persists, the EDC/ECM may have an internal hardware defect and require replacement.