Can't fire up. Buzzing from the relay, lamps blinkin- HELP

[Red]

"poorly maintained ae86's are PROBLEM cars... "
A poorly maintained *anything* is a problem car.

Meshin, I don't know what you've got but since there is an aftermarket air filter on it, I'm guessing the PO disconnected something and the fuse you are looking at is a "PO Special". Only the Gods know why it is there or what he connected those wires to. One thing you can be sure of, no car manufacturer will ever leave a fuse "hanging in space" that way. Every electrical code and standard on this planet calls for fuses to be secured to something, even if that means just a clip holding them to the trim. Maybe the PO put it in as an antitheft kill switch.

"Did anybody ever checked ground on ECU... with the body ground " Not me, I've never had any reason to do that. Cars are usually very poorly built compared to electronics, there will be some resistance across body points. Unless there has been water damage or another problem, the factory grounds usually are good enough.

"Did anybody have encouter blown Check engine light (the bulb) on the dashboard ?" Well sure, that's why every light on the dash is supposed to light up when you turn the key in any car. So you can tell if they are burned out, because sometimes they do.