Take a fuel pressure reading then call me in the morning.A fuel pump can become weak before giving out all together.Not the same car but A Mercedes 190e common issue ,I dont know if thats why they started installing 2 pumps on their setups after 1985 but Ive owned a few to find out how this can become an overlooked issue.Do this if your check list starts to dwindle down .I believe a diagnostic cost from a shop is just one hr of labor ,this would be well worth the cost for the fact they might catch other items that might leave you stranded paying for a tow, older cars are great as long as their not on back of a tow truck for simple small shi% .Does a Buick have a flux capasitor?