my 1990 prelude si at times is hard to start in hot weather. It turns over but won't start, after several minutes it will finally start. Seems to happen when gas tank is full or near full. Releasing the gas cap helps it to start sooner.

 

bad fuel pump possibly? I would remove the fuel line to the fuel rail and verify that it is getting decent fuel flow when you turn on the ignition

 

i would check the fuel pressure at the fuel rail. a new in tank fuel pump runs about 100 bucks. good luck

 

check the main relay. usually when a main relay goes bad. it is usually hard to start on a hot day.