I have a 2004 f250 6.0L diesel w 150k mi, the WATER IN FUEL light keeps coming on. I have drained the HFCM twice and changed both fuel filters . The light will illuminate after a few minutes of engine running and stay on till engine turned off. The engine runs smooth with no problems or other instrument gauge problems. What's going on here ?

Do you have an under hood water drain valve that needs purging, located near the under hood fuel filter?