I felt unusually smart when confronted with a Civic DX that refused to start when hot and I concluded that the Main Relay was likely the culprit--a diagnosis supported in retrospect by the eleven pages of hits one gets by giving Google "1990 Honda Civic Main Relay."

So I bought one, and now I feel unusually stupid because I simply cannot find the relay in the car itself!

I checked the whole area around the fuse block thoroughly and then the surrounding area equally thoroughly. I even looked at great length under the hood, though I would guess that it has to be inside the passenger compartment.

Pride swallowed, I have registered so I can ask: Anybody know where my nice new relay goes?

 

The main relay is located inside the car on the driver's side. Look above to the left of the hood release lever.

 

There are also other relays etc on the BACK of the fuse pannel inside the car by your hood release 9 atleast on my accord i assume its the same on our 91 civics).

 

The relay is stamped "Mitsuba" and is usually brown in color. Says a website I recently viewed hope it helps.