@roger,
a missing gas cap will **** up your vapor recovery but it shouldnt have any effect on starting an Old 240.
They were carburated werent they?? so there was no need for any pressurizing the fuel system for the gf injection system like some of the hybrids.
Uhh, Just looked up and saw that there were some 240 "D's" (diesels) in 88-93 . Do you hve a diesel? If so, thats easy to fix, first, get a fillup can of fresh diesel, the just run a SMALL(,1 pint) bottle of methyl alcohol into the fuel line to clean out the water.