Why would a 1989 Honda Prelude not start when warm?

Answer 1

Just my two cents but... it's possibly the same "main relay" problem which plagues many of the Hondas around that time-frame. Hot weather non-starting is usually caused by a faulty main relay. A new relay fixed my '90 Civic. Good luck. The main relay is what sends power to the fuel pump and ignition. If it's faulty, the engine will crank and crank but won't fire. I believe the main relay is typically under the dash on the driver's side. Note that it's inside the car, so it's the interior temperature that causes this problem. As a temporary solution if you're stranded somewhere, simply air out the car as best as possible and it should start again. The solder joints connecting the relay to its little circuit board crack, and in high temperatures will pull apart so the relay loses contact and can't function. One option is to replace the relay with a new one, but that will run you $70 or so. (!) A simple alternative is to just resolder the pins. Re-melt the solder on EVERY pin even if they don't look bad to the naked eye. Pop it back in and you're good as new.