Car will start but stay running

Whenever my car is just idling in park or just sitting still for very long you can smell strong gas smell today after about 15 minutes of idling in park I shut if off and now it will start but then dies It acts like it’s not getting gas

Never a good thing. You may have a failure in the fuel line, based on your description. The gas has to be going somewhere. Does it leave a puddle? If so stop trying to start it, don’t smoke around the car and have it towed to a mechanic!

Smelling gas is an indication it IS getting gas, not IS NOT getting gas. Issue is its getting too much gas so maybe you have a fuel pressure regulator ruptured or something or a leak in a line. But check pressure and the regulator.

The gas odor problem needs to be corrected asap b/c it is a safety issue. There’s another possibility for the starts ok but immediately dies problem though. If you buick uses a conventional distributor and the types of ignition system that uses a resistance wire to power the coil. With that configuration during cranking only, the resistance wire path is shorted out by a non-resistance wire. So if the resistance wire path is open circuit, it will crank and seem to start, but as soon as you turn the key from start back to run, it will die.