Technical Service Bulletins

Water in Diesel

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Water in Diesel

Some 1999-2010 Ford F-350 trucks equipped with a 6.4L, 6.0L or 7.3L diesel engine and a 40-gallon fuel tank located behind the rear axle may exhibit water in the fuel tank. This is due to snow and ice accumulation around the mushroom vent cap melting and being pulled into the tank through the mushroom cap.

Typically one to two ounces of water will get into the tank and will be caught by the horizontal fuel conditioning module (HFCM). Symptoms for this issue are WIF light on (water in fuel). The FCM/HFCM acts as a primary fuel filter/water separator which removes both water and impurities from the fuel. The engine-mounted fuel filter and the FCM/HFCM filter should be changed at the recommended service interval. According to Ford, this is not applicable to rain, road splash or incomplete chassis cabs sitting in storage. The vent will only ingest water if the vent is surrounded by ice or snow.

1. Remove the existing mushroom cap installed on the vent port of the fuel tank and discard.

2. Install the hose end of the new vent line assembly onto the vent port and secure with a constant tension clamp.

3. Route the new vent line assembly forward, on top of the tank, to the number 5 crossmember and under the fuel lines.

4. Secure the end of the new vent line assembly to the crossmember with the supplied strap, at the large circular hole in the middle of the vehicle.

5. Install the new mushroom cap at the end of the vent line. The cap must be positioned horizontally to prevent water from collecting in the new cap.

The new vent kit is available as P/N 5C3Z-9S327-A.

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