New starter, still won't start!

[Hawk24]

So I was driving my explorer a few days ago, pulled up at home and parked it. A little while later I went to go start wiring up my new sound system, 4 new speakers, sub, amp, the whole lot. got the speakers in fine and they sound great. Started running the wires for the amp and had the power wire for the amp hooked up to the battery but ran outta daylight then, so I packed everything up, reconnected the negative battery cable, went to go start it and nothing. All my interior electronics work like normal, I've checked all the fuses, and just nothing. Starter solenoid clicks like it should, battery is good, tested both by a parts store and myself with a multimeter, i got 12.54v. So I assumed that by dumb coincidence the starter died on me at the same time I started to hook up the sound system, as my explorer is over 209k and the starter looked in bad shape. I pulled it, had it tested at a parts store and was told it was toast. Bought a new one today, got it in there, and the exact same symptoms persist. I'm confident that the starter did or would need replacing soon because of the kind of shape it was in (rusty, very gunked up, one to one and a half inch long crack in it), however it still won't start. Is it possible I don't have the starter gear lined up with the flexplate correctly or something? Help!?

 

[Hawk24]

Update

Got the starter back in and replaced the fender mounted solenoid. It starts when i jump the solenoid, so I have an electrical issue somewhere between the key and the starter solenoid. Other symptoms: no headlights, turn signals(won't even turn on in the dash, try to turn them on and absolutely nothing happens), or power windows. Tips on where to start looking?

 

[explorerbob1]

I had a similar issue in my 97. Wound up being my neutral safety switch. Considering the stereo install, try wiggling your shifter lever? Assuming it's an automatic that is. Good luck!

 

[Hawk24]

Replaced the ignition switch and still nothing.

I was thinking neutral safety switch but that wouldn't explain the headlights, turn signals, interior lights, tachometer (recently discovered that doesn't work either) all not working as well. I did try wiggling around the shift lever and i even had the key push all the way as if i were trying to start it with my foot on the break and I worked it through all the gears up and down. Nothing happened. I did find a big yellow relay near the ignition switch and I can't figure out what it goes to. Thinking it could potentially be the culprit cause it looks important.

 

[Stumpy33]

Hawk24 . Did you resolve your problems above? And did you find out what the big yellow relay is for??