Honda Repair: 1991 Honda Acoord EX Sedan, honda acoord, hot weather


Question
Lately i have had trouble with the car not wanting to start when the weather gets warm. It will always start in the morning and operates normally as long as its reasonably cool outside. Sometimes between noon and 4:00 when its the hottest the car will just turn over but will not start. If you wait until the weather cools down the car will start up and be fine until the weather gets warm again. It doesnt seem to be influenced by the temp of the engine since it usually happens after my daughter has left it sitting at school all day and the engine is cool when the problem arises. The car is in the Chicago area and i am located in California so im trying to help her get it repaired via long distance. I know the problem she's experiencing because when i had the car in my possesion last fall it happened to me a couple of times, and when i would go to start troubleshooting it the car would start and be fine. As the weather got colder the problem went away but she has started to experience it again since the weather is warming up there. The car has approx 230,000 miles on it.   The water pump and timing belt were changed per schedule.  The fuel pump is the original but the filter has been changed. The car is completely stock.  Thanks for any help.

Answer
This is common problem.
I can almost guarantee you the culprit is the Main Relay.
It powers the fuel pump, as well as the ECM and rest of the PGM-FI system. It is located under the dash on the left side. It will be hard to find if you don't know where to look. It's hidden behind the Cruise Control Unit, and has a brown connector and a grey case. The wires are pretty good size. They aren't fun to replace if you've never done one, but the local Honda dealer or shop can do it pretty fast.
The only other common hot weather item is the Igniter, which is inside the distributor, but go for the relay first.

Good luck!