It's the "master relay" located under the dash. It clicks when you turn the key and you hear the fuel pump pressurize. Part no is usually RZ-XXXX and you can get em at the Honda dealer.
It should be under the dash and takes 5 mins to swap out, matushita RZ-XXXX it is called the "main relay" which does both the fuel pump and ignition. Assuming this is fuel injected. Just replaced mine in my 86 Si and it fixed problems with the pump not coming on all the time when starting. $70 from the dealer.