2004 Western Star w/460 Mercedes turns over but no start

A few weeks back, I shut my 2004 Western Star off. When I restarted it, it ran very rough at idle and had ZERO throttle response. I opened the drain on my davco (spelling?) filter for 2 seconds and it cleared right up. Put around 1,500 miles on the truck and sure enough it did it AGAIN! This time I decided to do a complete fuel filter change. Fired it up and it ran the same, rough idle and zero throttle response. Hooked up handheld scanner to read check engine code. It registered the throttle position all the way from 0-100%, so that tells me the throttle sensor should be good. I tried putting air thru the fuel tank, cracked the lines. Now it won’t start at all. I even used the 1 gallon pump spray bottle with diesel to try to prime it thru the primer fitting. Still nothing. I could hear fuel leaking back into the fuel tank constantly while I was trying to prime it, so I replaced the fuel check valve. Still nothing. Won’t fire, won’t even smoke when it cranks. I’m at a loss. Any help is greatly appreciated. I’m not a mechanic by any means, so please forgive some of my terminology. I just want my truck fixed!

 

Thank you! I’ll give that a try