i have a 1991 accord lx 4dr and it wont start sometimes.
always starts when its cold out but just on sunny afternoons it doesnt
sometimes i wait 5 minutes and try it again and itll start but sometimes i wait and it still doesnt start and it ruins my whole day

any help?

 

Before you try to start the car, turn the key to the II position and try to listen for the fuel pump to turn on for ~2 seconds in the middle of the clicks.

It is a faint whirling/buzzing sound that will come from the back seat area. Listen at the gas cap (w/ cap removed) and have someone else turn the key for you.

If you do not hear the pump prime when your car is not starting, then replace or repair the main fuel relay.

See for how to repair: http://www.techautorepairs.com/mainrelay.html
See for the location: http://www.techautorepairs.com/mainrelaydefine.html

 

Especially if it happens with a very hot interior.

So it doesn't start. You sit for 5 minutes with the doors or windows open & the interior cools down, then it starts. Sound like the situation you have?