i recently bought a 94 7.3l idi f350. The people I bought it from said it was losing fuel pressure. The manual fuel pump had gone bad so I replaced it along with the lines, the IPR valve and put new gaskets on the banjo bolt. Tried to start it yesterday and it ran for 5 minutes and died. I put a gauge on the Schrader valve and when it first goes to crank the pressure goes up to 40 then drops to around 25 and slowly goes down. I can not find any fuel leaking anywhere but am losing fuel pressure somewhere. I was thinking maybe the Schrader valve needs to be replaced? It unscrewed relatively easily. I also cleaned both screens connected to the fuel pressure regulator, changed the fuel filter, oil filter and new oil. Any advice would be greatly appreciated. Thanks