Sounds like microorganisms and fungus growth, dead carcusses, and excessive amounts of umm by-products aka pooh..
Fuel treatments may kill or stop 'em, but does little to flush em away..
New Tank, new sender? If so, did you install a new Fuel Strainer (ACDelco TS 1012)?
Did you thoroughly flush the entire system when you replaced the fuel tank?
If not, possible you recontaminated the system ie quickly clogging the new incorrect gasoline sock.?.?
Ever run bio fuel or alternative fuels? If so, dont..
With engine running, there should be fuel pouring out of the WIF drain valve when opened. If not, typically indicates LP isnt working or is faulty..
Note your supposed to drain aprox a liter of fuel from the FFM every time you fill up, at least once a month. Thats how this system "strains" off free water that naturally collects in the tank.. This regular maint procedure isnt done on a regular basis if at all (not unless WIF lamp flashes ON) so its common to find a pile of crap in the bottom of the FFM housing.. If its been neglected for some time, the WIF drain port may be clogged full of it too..
Unrestricted return line is equally important..
A starving lift pump can quickly become damaged, even if its brand new.
Given how solidified that looks.. I would inspect the entire fuel supply ans return system for any more possible restrictions..
Last edited by HeavyChevy95; 11-16-2015 at 07:33 PM.