The 6.4 Ford Powerstroke engine’s low-pressure fuel system uses a Horizontal Fuel Conditioning Module (HFCM) to pump fuel from the tank to the engine. The normal operating pressure is 3-8 psi. On the 6.4 applications, a Schrader valve test port is provided on the fuel cooler assembly.

The HFCM is mounted to the driver’s side frame rail, and pumps fuel from the tank to the 4-micron secondary fuel filter that’s mounted atop the engine beside the oil filter assembly. After passing through the secondary filter, the low-pressure fuel enters the mechanical High Pressure Fuel Pump. The PCM uses the HPFP’s two control valves to control fuel entering the high-pressure system. The remaining fuel is directed to the fuel cooler. The cooled fuel will then be directed back to the secondary fuel filter and lastly to the HFCM.

 In addition to a filter and an electric fuel pump, the HFCM contains a Diesel Thermal Recirculating Valve (DTRM). The DTRM determines the flow direction of the low-pressure fuel returning from the secondary filter housing. If the fuel being drawn from the fuel tank is cooler than a specified temperature, the return fuel from the secondary filter will be directed back to the engine. If the fuel from the tank is not too cold, the return fuel will be directed back to the fuel tank.

 POWER TIP: The PCM cannot monitor the flow of fuel volume supplied from the HFCM to the high-pressure pump. Restricted fuel filters (or anything else that may limit the flow of low-pressure fuel to the high-pressure pump) can cause catastrophic pump failure, which may result in debris in the fuel rails and injectors.

 The HFCM also contains the Water In Fuel (WIF) sensor that illuminates a light on the dash prompting the driver to open the water drain on the module. Ford recommends draining the water out of the HFCM at regular intervals and when the WIF lamp is on. The WATER IN FUEL light will come on when app