No thoughts needed. Replace all three now! OK so I guess that qualifies as a thought…
In the first picture showing the black cable on the left side of the starter relay, it really looks like a fairly new cable, but it also looks completely compromised.
Is it just the angle of the camera or the lighting, or is it actually swollen where it curves?
Swollen cables are bad juju all around.
And please please please make the two positive cables RED and the negative cable BLACK!
Please please please.
Don’t scrimp at this point either and get at least 4-gauge cables. I prefer 2-ga.
Doesn’t matter why, I just think a little overkill is a good thing at this corner of the engine compartment.
What is the large red cable with all the tape around it? Is that the engine ground? And is it as hacked as it looks?
I know a lot of people mix up one color or the other over the years, but to have the colors actually reversed from what they were supposed to be is an accident waiting to happen.
Not necessarily by you, but by any unsuspecting helper or mechanic that’s working on the engine at some point.
Even if it this point, they had nothing to do with your problem, they look so far gone that this is something that I would have to say needs to be replaced.
I agree that you don’t replace parts with new ones these days without verifying that the old one is bad. But a battery cable that looks as bad as yours needs to be replaced.
So, if possible, get a reasonably short (and red!) 2-gauge positive battery cable to go to the left side of the starter relay.
A reasonably sized 2-ga starter cable from the right side of the relay down to the starter.
And a reasonably sized (and black!) 2-gauge negative battery cable to reach the engine.
And by reasonably sized, I mean, as short as possible to keep the length reasonable, but as long as it is needed to be able to keep them, tucked out of the way of items, they shouldn’t be near. Such as exhaust, manifolds, spinning fans, sharp edges, etc.