stalling problem

have a 1987 buick century 2.5l tbi
it runs great then you cut it off and it won't start for nothing,
it will also stall out and won;t crank back up,
if you spray starting fluid in it it will start and sometimes it will keep running and other times it wont- help please
have tuned it up-changed fuel pump-fuel filters-fuel pump is working, you can here it-changed the fuel relay--what else should i be looking at?????????