1990 Accord starts when cold, but difficult to start when warm. Example: Go to store, come out car won't start. Starter turns engine over. If I wait 5-10 minutes car will start. This is an intermittant problem (not everytime).

 

On About.com they mention the Main Relay as being the most likely culprit.

 

Where is the main relay located?

 

If you do a search on "main relay" in this forum or on google you will found tons of info.

 

The main relay is located under the drivers side dash board near the steering colume. Comes off with a 10MM socket. If you lay on your back and look up under the drivers side dash you will see a good sized gray box with a pretty big plug on it. That is the main relay. They are very comin to go bad.
Also may want ot check the dist. cap and rotor, coil and ignitor. These are comon parts to go bad as well.
Hope this helps.

 

How do I get the main relay out. This appears to be a BIG problem. Thanks.

 

I did remove a good sized grey relay,but, it was the cruise control relay. Oops! The smaller grey box with large brown plug is way up there.

 

My friend had a 91 accord that suffered from the same symptoms. It had a difficult time starting during warm days? We switched main relays...he used my 6th gen accord main relay, and he had no problems ever since.

The main relays look alike, but the 91 accord had a thicker plastic piece covering/protecting the unit. Thus, keeping the heat within.

I don't know if the 90 and 91 accord are the same, but try to use the main relay from a 6th gen accord.