I have a bare bones stock 16 valve 1990 honda civic lx. Ive noticed lately that on hot days 80 degrees plus that it will not start but turns over just fine. Any advice?

 

I've heard that one of major culprits of no starts is the main relay. consider either resoldering some of the joints or purchasing a replacement.

I believe that it you can hear the fuel pump priming, it will eliminate the main relay as your culprit.

do a google search on main relays on civics and you'll see a lot of chatter on it.

 

I was having this problem last summer and a buddy (former Honda mechanic) told me to try this:

Under the dash on the driver side, closest to the door, there is a BROWN connector. Unplug it and plug it back in. This worked fine for me several times. I'm not familiar with what this box is, but hopefully it helps.

Sorry, I know that isn't a very technical response, but it worked for me.

 

Consider going to the following website to find out the location of your main relay:

http://techauto.awardspace.com/civicrelay.html

Here they show you how to resolder the joints so that it will work.

http://techauto.awardspace.com/mainrelay.html

apparently they used some low quality solder when it was manufactured.

from the pictures of the first link, it is brown in color.

 

That plug goes into the main relay. The relay is mounted on the side of the car right above the lever that opens the hood. If poking around the main relay fixes it, you should remove the relay and resolder it, or replace it. Otherwise it still has the bad connections and its going to break down again.