I would trouble shoot the battery and starter first.
1. I would take jumper cables directly to the starter to see if it will engage. If not, check battery; try a known good battery. If battery good, pull starter and take to shop and have tested. Bad, buy new starter.
2. If that works, I'd take some power to the soloniod and see if it engages. If not, buy new solonoid.
3. If that works, start checking your ingition switch and wire back to same.
Hope this helps.
85 CJ7 4.0L/SM465/Dana300/AMC20/Dana30, MPFI,154K miles - 33" 12.5's Pro Comp MT's, one piece axles, Detroit Softlocker rear, Lock Rite front, Warn Hubs, 4.56 R&P, 4" BDS lift, Warn x8000i, Warn winch guard, Hi-Lift, Tuffy console, Four X Dr. rocker guards, Rock Hard sport cage, Kilby OBA with 1.75 gal tank and York 10.3cc compressor, Tube fenders by GenRight Offroad, Fabricated rear bumper and tire carrier.