6.4 Liter Fuel System Failure
The 6.4-liter fuel system has been especially sensitive to contamination do the close tolerances of both the high-pressure fuel pump and the injectors.
The best way to avoid fuel system issues is to properly maintain fuel filters and drain intervals on the HFCM-lower fuel filter water drain cock. Ford recommends draining the water separator every 30 days of use regardless of the status of the WIF warning (water-in-fuel, warning).
Fuel system components use diesel fuel as a lubricant and coolant. Any contamination such as water which passes through the high-pressure pump and injectors will cause rapid damage to them. Low fuel volume or lack of fuel to the high-pressure pump will cause galling and seizure of pump components. In the early stages of high-pressure pump failure, particles of metal from the high-pressure pump will contaminate the pressure regulator and make their way into the injectors. These particles will cause rapid wear of the injectors leading to an over-fueling condition and complete injector failure. Over-fueling can lead to catastrophic failure of pistons which will essentially melt and destroy the engine in much the same way as accumulated oil in the CAC system. Water in the fuel system can also cause rust to form on the non-stainless steel and iron parts such as internals on the high-pressure pump and fuel rails.