The seals (like any that sit and dry out) have problems. Pump needs to be FULL of oil (test fluid I would guess is ok, better than modern fuel for sure. Has to be ran through the pump (out injector ports).
Then spray with cosmoline, store in vacuum container. Best diy container I’ve seenIs the steel ammo can. Drill 2 holes, one for small vacuum gauge the other you add a schrader valve. Hook up your ac vacuum pump and bring it all the way down. Store on the shelf and check once or twice a year by glancing at the vacuum gauge.