Fuel Coagulation

It is, or should be common practice for technicians to drain the fuel water separator during regular services. We have discovered that some drain valves have failed to allow fuel and water to drain and in some cases the valves leaked from the vent at the top of the valve instead. We have once again discovered that water is reacting with the fuel, or something in the fuel, creating a whitish, greasy substance that builds up in the collection bowl. This substance does not flow and cannot be removed by draining the water separator. Below is a close up image of a water collection chamber in a HFCM from a 2009 Super Duty truck with a 6.4L PSD engine. The red arrow is showing the water sensor.

The result is reduced water collection capacity, blocked water drain valve ports, continuous water in fuel (WIF) warning light illumination and possibly an inoperative WIF light due to contamination of the WIF sensor. In a worst case scenario these conditions could allow water to pass to the engine fuel system causing driveability concerns, damage to the fuel injection system and even catastrophic engine failure. If you encounter a 2008 or newer Super Duty truck with a 6.4L engine that has a fuel water separator drain issue or a repeat WIF light concern it might be a good idea to remove the fuel conditioning module (HFCM) manifold to inspect the collection bowl for this substance and clean it out. Be aware that the rubber HFCM manifold gasket may have swollen or stretched and cannot be re-used. It is important to note that fuel samples from the affected trucks we have seen appeared to be clean ULSD but were not analyzed by a laboratory.

If you are going to service the water separator you need to remove the manifold cover and the rubber gasket usually swells or sticks causing it to stretch. Whether the water in fuel sensor is actually fouled or just needs a light cleaning, removing it usually damages it preventing it from locking in place and sealing properly. Use these part numbers as needed:

• 8C3Z-9276-A - Gasket and Hardware Kit
• 8C3Z-9C264-A - Water In Fuel Sensor

As for cleaning out the water collection chamber it is best to begin by simply scooping out as much as you can with a finger, wooden dowel or a small screwdriver with a rag. Combustion chamber cleaner can be helpful in breaking down residual paraffin or Brakleen has proven effective as well. Finish up with compressed air and reassemble with a new gasket, bolts and sensor as required.