Case IH 3928 – Engine Control Unit (ECU) / EDC (Electronic Diesel Control): Fuel pressure control Metering unit: Exceeding of a maximum peak pressure at empty fuel tank

This code indicates that the fuel rail pressure has exceeded the maximum allowable peak pressure limit, and the system has detected that this occurred while the fuel tank was empty (or extremely low). Running the tank dry introduces air into the fuel system, which can cause erratic pressure spikes, cavitation, and loss of control over the fuel metering unit (MeUn).

• tractors
• combines
• sprayers
• Patriot series

1. 1

   Verify the physical fuel level in the tank. The code is specifically triggered by an empty tank condition.

2. 2

   Install a test line constructed with clear tubing at the inlet of the high-pressure fuel pump. Run the engine loaded and unloaded to observe for air bubbles. A steady stream indicates an air leak.

3. 3

   Connect a pressure gauge between the fuel filter and the high-pressure pump. The pressure should be a minimum of 5 bar (72 psi) with the engine loaded or unloaded. If pressure drops below 0.276 bar (4.0 psi) during tests, there is a restriction.

4. 4

   Check the fuel pre-filter, main fuel filters, and Voss O-ring fittings for clogs or leaks.

5. 5

   Inspect the bottom/sidewalls of the fuel tank for debris that could be restricting the pickup tube.

1. 1

   Refuel and Bleed

   If the tank was run empty, fill the fuel tank and properly bleed the low-pressure and high-pressure fuel systems to purge all trapped air.

2. 2

   Clear and Retest

   Clear the fault code from the EDC using the EASy diagnostic tool. Run the machine under load to see if the code returns. If the code was simply caused by the operator running out of fuel, this will resolve the issue.

3. 3

   Resolve Restrictions/Leaks

   If the clear-line test showed air ingress or low supply pressure, replace the clogged fuel filters, replace leaking Voss O-rings, or clean the fuel tank as required.

4. 4

   Replace the Metering Unit

   If the low-pressure supply is solid (5 bar / 72 psi minimum), no air is in the system, and the code persists, the Fuel Metering Unit (MPROP) on the high-pressure pump has likely failed or become mechanically stuck due to lack of lubrication from running dry. Remove the defective metering unit from the Bosch CP3 pump and install a new one.

5. 5

   Final Verification

   Clear the codes again and test the machine under a hydrostatic stall or dynamometer load to ensure rail pressure tracks the setpoint without spiking.