Sig Sauer

I have a 99 Xj and over the last month or so at random times it would have a hard time starting as if the starter was about to go but would start up on the second or so key turn. Then last night I could not get it started. When I turn the key to the first position I loose all power inside the jeep like the interior lights. If I try and crank it nothing will happen, not even a click of of the starter and all power is still out. When I return my key back and to take it out the interior lights will come back on. Here is where it gets even more strange, if I just put the key in the ignition (not turn it at all) and I press the brake pedal, all power is cut to the interior lights.

Here is what I have done.

Check the battery, its good
Checked the fuses under the hood, they are all good (except 2 small fuses only read 8 or so volts but they are not blown)
Checked the power cable leaving the fuse block, its good
Checked the power cable where it attaches to the starter, 3 volts with the key in the ignition and only clicked over once. This has confused me even more as I am under the impression that the cable departing the fuse block is a direct run to the starter.
Tried to jump the starter but my starter solenoid does not have three posts, the ignition is a type of single wire harness so screw driver does not work.
Tried using a external ignition that I use for my dune buggy with one connection to the battery and the other on the ignition wire with the key in the on position and nothing.

I have considered the NSS, maybe starter relay... but the power being cut to the whole jeep when I turn the key one click or press the brake pedal has me stumped. Can someone recommend what I should test so I can figure this out? I can post pictures of these reading tomorrow morning if you all would like me to, just let me know what readings to take and in what position the key should be in. Thank you all for your help.

OldTires

Check your ground wires. Do a google search for your year jeep and ground wires. Find them, check them and clean them. Do that first.

IJM

Yup, ground wires, but it may also be the battery clamps and cables. My positive battery cable and/or clamp is failing and produces simular symptoms.

tjwalker

Grounds can be the root cause of many electrical gremlins. Refreshing grounds is NEVER a bad idea, and the investment of your time in this procedure is always well worth it!

You can't tell much of anything by looking at ground connections!! You must remove, scrape, clean until shiny the cable/wire ends and whatever they bolt to. Be sure to remove all paint from any ground connections.

Start with the one on the back corner of the head, and where it attaches to the firewall, as it deteriorates over time and is an area that makes it susceptible to damage. Best to replace that woven cable with a #4 or #2 gauge cable. You can attach the one end to the intake manifold if you would like.

Next go over to the engine dipstick tube stud. Remove the nut and clean the wire ends and scrape the block until shiny at the stud. Reattach tightly.

If you are so inclined, add at least a #6 cable from the negative terminal of your battery to one of the bolts on your radiator support.