one voltmeter test would have saved all that work and grief.
do you have a voltmeter, dvm,dmm, dso, or gmm?
any even a $3 harbor fright meter?
no need to guess ever again.
its all here.
Engine-will-not-crank-over
keep an open mind and use the meter to show the real problem.
see the last photo. see the meter?
if you cant get full power to the starter , it will never start, correctly and reliably.
My first guesse (you asked)
is the battery cable on top of the starter (ground main from batterY) is not bolted securely to the top mount of the starter.
2nd guess. (bad with out data)
bad battery cables. (internal corrosion)
i bet the car will start by wiggling the battery cables or the start key line is bad.
3rd guess.
bad PNP tranny switch , wiggle that. wiggle that shifter ! while cranking attempted.
#1 test are:
hot wire the starter solenoid , if it starts then the starter key line is bad.
if not , then starter power is bad.
left field , mangled flywheel ring gear.
but the voltage test will fail due to overload on starter.
__________________
http://www.kick-fix.com/
IS YOUR CHECK ENGINE LAMP ON ? running.
96 Tracker, 5sp, 2Dr,4w,d OE stock.Fed48+No A/C ,No Cruise. +MPG gauge , live dash fuel pressure , oil pressure and voltage gauges. + fur lined gimbals beer holder with IV drip mod.