Got a repair manual for your '88 LX? The 'main relay' is a combination relay to power the fuel pump, ECU, & fuel injectors. Since you don't have injectors, Honda probably did something slightly different for the carbed cars. Like maybe a normal-looking relay instead of a long one. The PGM-FI 'Main' relay is really just 2 or 3 relays combined into the same case.