gentlemen:

my truck (94 IDI non turbo) ran about 3.5 quarts low on oil. I never drive it and it sat and leaked for a while i guess. The engine began idling low, and would surge and hunt around for a while. after I added oil, its still doing this. Are these trucks' injectors driven off engine oil? Could low or dirty oil cause this issue? The truck was treated badly by the PO. Should I do an oil change?

Also, for oil changes, if I think the oil passages might have crud in em, is seafoaming the crank case before draining oil a good idea? or will it thin the viscosity and kill the injector pump?

Im willing to accept it might be the water seperator, as I also power washed the frame and a little around the engine bay (tried to miss the important bits) but I didn't know where to start and the oil only has 2k miles on it. maybe less

 

if its not power stroke it dont have a high pressure oil pump to drive the injectors
i would check or bypass the water fuel seperator that was my big problem after i tried to drain water from it it never sealed off after that.
but you preasure washed the under side so you could have ruptured a fuel line.look for a wet spot on the fuel line .