Car doesn't start in hot weather

I have a 1998 Honda Accord EX-V6 coupe. It has a peculiar tendency to not start if it’s been standing in the sun for a period of time longer than 3-4 hours. It will not start until it has cooled off in the shade for about 1 hour, then usually works without problems. This is becoming increasingly frequent. The car has a new battery and I just replaced the fuel pump. Occasionally, it doesn’t start for 15-20 minutes after a fill-up. What could this be?

PGM-FI relay under the top of the dash gets hot, and doesn’t work until the windows/doors are left open a few minuets for it to cool and begin working again. Go to Then, click on appropriate symptom.