1998 Kia Sportage hard to start

Re. . Quires long crankingh time and 1/4 throttle togetrunning. Only oner cylinder sounds ki like it fires during cranking BUT once it gets going it idles fine and has normal power, which has always been weak anyway. Has new plugs, no oil in plug holes, compression is normal and timing belt has been changed and definitely timed correctly. Obviously a spark problem because sprating stasrting ether into the plenum has absolutely no effect on starting. We smell thge ether come out the exhaust. This problem was preceded by three cycles of overheating after radiator hose slipped off. Then we used a vacuum system to refill the cooling system, which cured the overheating.