So after a week goes by of my Fc not wanting to crank I replaced the main fuse, and go a new battery. Well my old battery tested fine and after my buddy messed with the main fuse it started up for 2 days no issue now it won’t start up at all. Any ideas?

 

Another not when pop starting it with old fuse it would misfire. Since I got a new fuse if I were to pop start it will it run normal with the strong connection?

 

Pop starting it?

 

Sounds like you need to get involved with the electrical system and check or replace you’re power and ground wires. They can be old with too high of a resistance.

A multimeter will become your new friend.

 

Dr Knight is correct. I'd bet money that your battery cables are failing. The Ground Cable is notorious for this, as it corrodes from the middle terminal (body) outward, making all sorts of gremlins pop up. This is because it is the "spine" of the electrical system that every circuit runs through to obtain their ground connection to the Battery Negative Terminal.

Also, unless the fuse(s) in question are blown, replacing it wouldn't make a difference. There is only one time I've experienced an exception to this. It was a Scosche "100 amp" fuse from the ricer aisle at Walmart and didn't actually blow. There was a thread of the connection still holding it together after it saw 100 amps (Starter on manual trans). So I took it as a lesson to get the proper parts for a battery relocation and never looked back.

Power to the starter does NOT go through any of the fuses. Only the Start Signal from the Ignition Switch does. Can't recall the fuse rating offhand, but it's 10A on the Eunos Cosmo. Pretty sure it's about the same here.

 

I agree with checking the main ground cable by the battery. I would also clean up the other grounds in the engine bay (Link Below). One thing to look into is the signal wire that goes to the starter. I had that connector come loose after driving and the car wouldn't crank.

FC Grounds