I do not know what the 30 terminal is but there is two ways to burn out a relay one to much holding voltage ( as maybe a regulator , diode, whole alternator over charging , I would think though this would show up elsewhere too.) or to many amps being ran thru the relay on the load side, I would think this is the most likely, so figure out what 30 controls and disconnect it and put a amp meter in series in the circuit and see what it is pulling amp wise. Look for bad wiring shorting to ground and if you were to get lucky disconnect the fuel relay and see if that is involved.
