If it's an '02, it's a 7.3. Check the valley pan between the heads, most leaks are in this area, fill up the pan, and overflow coming off the back of the motor and down the side of the bellhousing. The most common leak is the fuel pump, located behind the filter housing and in front of the turbo, deep in the pan, not cheap, not easy to get to. Another common leak is the fuel filter vacuum sensor, on the side of the filter assembly, mine started leaking and I just jerked it off and plugged it with an 1/8" pipe plug, who needs it? Other than those two, check the filter and all the lines in that valley pan, a good place to start.
cfpinz