I also had same problem I have 4000 watt amp and as soon as I wired it fuse got blown and I don’t know because we did pretty much secure wiring now the wiring kit I used for it was 1500 watt with 5plus gauge. So can someone suggest me which fuse size I should go with for 4000 watt amp and if the 5 gauge wiring is good enough for my setup .
wow. Ok. So I promise you I am trying to be polite when I say this:
Based on this little bit of information, stop touching your system, and take it to a shop. You don't have 'no basic electrical knowledge', it's worse than that, you have incorrect electrical information. Based on this, I think there are MOST LIKELY other aspects that are wrong, that will get overlooked, because you don't know what to look for, or have wrong information, and there is potential danger.
(I PROMISE YOU, I'm not trying to be rude saying that, just trying to help in what I think is the best way).
To answer your question. Stop. You can not use 4awg or 5awg on a 4,000 watt amp. Go read the manual, which should tell you what size, or what size fuse. You need a fuse that is at or more than what your 4,000watt amp needs, and you need a cable that is capable of more than the fuse.
There's too much going on here, that I'm not in the mood to write. That wire can't handle that amp. You need to learn a lot more, or take it to a shop.