What's the problem on dad's truck?
It's sucking air into the fuel system somewhere. At first I thought it was the fuel pickup in the tank as all the 99 to 2003 F series Diesels have an issue with the plastic pickup deteriorating around 200,000 miles. So I pulled the bed, it's quicker and easier the dropping the tank. Replaced the pickup even though it didn't look bad and took apart the sending unit to clean the filter screens. Found a little trash in them, but no real issues. I also replaced the transfer pump on the frame rail and that didn't make any difference, still getting air bubbles in the fuel filter bowel. So now I will have to break each fuel line quick connection and replace the O-rings in each joint. I'm at wits end on figuring this one out.