New Holland 3808 – ECU: Fuel Quantity Not Plausible At Low Idle

The Engine Control Unit (ECU) has detected that the amount of fuel being supplied by the high-pressure pump is not plausible or logical for the engine's current state of low idle. This indicates a discrepancy between the expected fuel quantity and the actual fuel quantity being delivered, suggesting a significant problem with fuel pressure regulation or delivery within the fuel system.

• C232
• C332
• T8.380

1. 1

   Check fuel quality for water, debris, or signs of gelling in cold weather that could clog filters and injectors

2. 2

   Inspect fuel filters, as a clogged filter is a primary and common cause for this fault

3. 3

   Inspect fuel lines and connections for visible leaks in the high and low-pressure circuits, or cracked/loose lines allowing air to enter the system

4. 4

   Bleed the fuel system according to the manufacturer's procedure if air is suspected in the lines (e.g., after a filter change or due to a leak)

5. 5

   Check for other fault codes (e.g., fuel rail pressure sensor) which could indicate an electrical issue rather than a mechanical one

6. 6

   Test fuel rail pressure at idle using a diagnostic scan tool and compare it to the commanded pressure (verify with a mechanical gauge if necessary)

7. 7

   Inspect injectors for tightness and leaks, and perform an injector return flow (leak-off) test to check for internal wear

8. 8

   Evaluate the high-pressure fuel pump's output volume to determine if it has low efficiency due to internal wear

9. 9

   Check for ECU issues, particularly on C-series loaders where service bulletins suggest potential malfunctions

1. 1

   Disconnect battery

   Disconnect the negative battery cable to prevent accidental starting or electrical issues before beginning repairs.

2. 2

   Replace fuel filters

   Locate and replace all engine fuel filters (primary and secondary). Pre-fill the new filters with clean diesel to aid in priming the system.

3. 3

   Prime the fuel system

   Prime the fuel system to remove all air. This may involve operating a manual priming pump or cycling the key, depending on the specific machine.

4. 4

   Clear codes and re-test

   Clear the fault codes with a scan tool and start the engine. Let it run at low idle to see if the fault code returns.

5. 5

   Perform advanced diagnostics

   If the code persists, proceed with fuel pressure testing and injector return flow tests to isolate faulty components.

6. 6

   Replace faulty components

   Replace any injectors found to have excessive return flow. If the high-pressure fuel pump is diagnosed as inefficient, replace the pump assembly.

7. 7

   Final system check

   After any component replacement, properly prime the system, clear fault codes, and perform a final test run to ensure the issue is resolved.