contact cleaning?

It's all described in the FSM, Engine Fuel chapter.

BUT, I just remembered the one situation where the pump will run with the key at On in the 1978 model.  If the oil pressure switch is disconnected.  That creates the "Open" condition shown in the table.  It's a flaw in the design, but many 78 owners use it as a trick to turn their pump on..  So you either have the wrong oil pressure sender or yours is broken, if that's the cause for the pump running.

Anyway, it still sounds like your rail is leaking down, whatever the reason.  I think that the CSV portion of the rail might not refill as fast as the rail itself, because it's on a branch.  drive your car, park it, the pressure drops and the CSV dries out because it's hot.  Turn the key on, the pump runs and you get pressure, but there's a bubble at the end of the CSV line.  So, basically like having no CSV.

Get your pressure to hold overnight and it will probably start normally.