Took my truck to the dealer on monday because it was running a little rough, and the check engine light came on. It took them three days to diagnose the problem as excessive water in fuel. They estimate cost to repair between 5 - 10,000 dollars. They are not sure, because they have never seen corrosion this bad, and are not sure how deep they will have to penetrate to get it all out. They informed me that this would not be covered under warranty. Truck is 2004 with 20,000 miles, exactly 1 year old. I had utility body installed right after I bought it, and my suspicions immediately pointed to that. I suggested to the dealer, that maybe the tank was punctured or otherwise violated during the installation of the truck body. I suggested they do a pressure test on the tank to see if it was air tight. The mechanic agreed that that was a great idea. They called the next day, and said they had figured it out. According to the dealer, diesel fuel tanks vent to the atmosphere through vent holes at the top of the tank. Regular gas tanks vent to the filler tube in a closed system so the voc's are contained. So obviously a pressure test wouldn't work on a diesel tank. The theory they are presenting to me is: When the new truck body was installed, the gap between the cab, and the bed was increased by 3 inches. This exposed the top of the fuel tank, that has a depressed area in the center, to the weather, and hose water when washing. They say the vents are in this depressed area, which would then act as a funnel to channel water directly into the fuel tank. Does this make sense? If the modification to the truck caused the problem, then the utility bed manufacturer should be liable. However, if Dodge put open vent holes at the low point of a plastic tank, isn't that poor design? Who do I blame? (besides myself for just draining the water out of the fuel filter every week, and not wondering why).