Engine/Transmission (1998.5 - 2002) Low Lift Pump Pressure - Contaminated tank?

[craigS]

I just put a fuel pressure gauge on my '99. It is reading after the filter on the filter housing. Just put a new filter in it. Also put in a new lift pump. The problem is that when first started after the truck has sat for a while, the pressure only rises to about 7-8 psi and then slowly falls to zero over a minute or two. If restarted immediately, the pressure stays at zero. If I wait 15 minutes or so the pressure will start at 7 or 8 again and drop. Now I'm thinking that there is a restriction at the pickup in the tank. Naturally the tank is full, now. Any thing else I should consider before dropping this tank to look for debris?