i've got the fuel sender out now and could immediately see why I was getting contaminated fuel even after draining the tank via the strainer and adding fresh diesel. The strainer/second tank compartment sits about 5/8" above the bottom of the tank. So if you have a fluid in the tank heavier than diesel it will sink to this lower portion of the tank and sit there. So, no matter why you do, if the drain the tank and add fresh fuel, that fuel will 'mix' with the crap on the bottom as the diesel sloshes around and contaminate the diesel. I assume it is designed this way to allow for a small quanity of water to sit in the tank and not get drawn into the fuel system. So, if I can clean out this pocket of crappy ****, I might be able to get a functional tank again. I'm thinking of sticky rags down thru the sender hole and mopping it up.
Here's a more radical and potentially dangerous solution--has anyone every shop vac'd a combination of diesel fuel/potassium hydroxide/whatever????
Ok--got a plan. I'll get a couple of gallon container with a lid. hook the shop vac suction into the lid extending just an inch or so into the container. Then, hook another line into the container extending down a few more inches but not to the bottom. With the lid tight, I should get suction from the second hose and any liquid sucked up should end up in the container and not in the shop vac.