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Success! I've learned way more about the 1991 Ford E-250 fuel system then I ever wanted to know. This particular rig was built with 2 fuel tanks and a fuel injected 351 Windsor V8. Each fuel tank has an internal lift pump. These pump into a mechanical fuel reservoir. 2 feed lines in and 2 return lines back. There is a feed and return line going out to the engine. Between the reservoir and engine is a 3rd pump which is a high pressure pump. 3 fuel pumps, Yippee! On my rig because it sat for so long the fuel solidified in the high pressure pump and it became stuck. I soaked the pump internals with K100 fuel treatment and it freed up after a day or so. The reservoir was a puzzle. It is really a mechanical switch that allows each tack to feed the engine. There was no mention of this in the manuals I have. I don't have the factory manual. Maybe its in there. Anyway I found a video on youtube posted by a farmer in Idaho which had all the info I had been seeking. Thank you, thank you! The switching mechanism seems to be operated by pressure moving a diaphragm up and down to accommodate which ever tank is pumping. sitting for years full of fuel didn't do it any good. I disassembled it and flushed it with K100 and lubed it with WD-40 until it moved up and down freely, reassembled it, primed it, and reinstalled it. I couldn't find a definitive answer as to wether or not there should be a filter element in the bottom reservoir cup. There is small lettering stenciled on the cup stating not to remove cup. (it unscrews from the main body) I had to take it apart to clean out the bad fuel in it. There was no element in it but when I referenced the Ford p/n it showed an element so I bought and installed one. There is another factory inline filter next to the high pressure pump so I think this is redundant. While I had the reservoir/switch removed I powered up the system by turning on the ignition switch to see if I could get the lift pumps in the fuel tanks to push fuel out of the lines. Nothing. This made me a bit nervous as I didn't want to drop the tanks unless I absolutely had to empty them and resurrect the lift pumps. I had dumped 5 gallons of fresh gas and some conditioner into each tank hopes that that would do the trick. When I turned on the ignition I could hear the hi pressure pump cycle on for about 10 seconds then shut off. But nothing out of either lift pump. Bummer! I thought maybe because it's a closed high pressure system it wouldn't cycle unless everything was assembled in place. I reassembled everything with the reservoir primed and tried to start it. It cranked for about 15-20 seconds, then caught and fired right up. I ran it for about 30 minutes and it was nice and smooth. No leaks. It smoke for about 10 minutes then cleared up. I'm real happy. I need to install the drive shaft, mount 4 new tires, change the fluids and shake it down. What I learned from this is that Ford used several different fuel systems on these chassis, some mechanical and some electronic. There sure isn't much information on any of them out there unless you really look.
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