When you bench tested it, did you put power to both the large terminal and the small one? Each have their own job to supply power to. Our starters are a little different than the older ones.
When you apply power to the solenoid, the solenoid will do two things. 1, it closes the contacts to allow power to the armature/fields. and 2, it engages the bendix to the flywheel/flexplate.
'02 F-350 "Babe The Big Blue Truck" 4x4, Ext. Cab, 8' bed, SRW
DP-Tuner 80T, 160cc single shots, GTP38R turbo, Ceramic coated IH up-pipes, coolant filter, 6637, DIY exhaust brake, openair CCV, propane, SBC DD all ceramic clutch, ISSPRO EV boost/pyro/HPOP pres./rear end temp, 4" lift, traction bars, 255/70R22.5 tires, York air compressor, 16 flashy lights, 12 strobes, 12 switches on console, 9 switches on the dash, 7 two-way radios, 5 air horns, laptop, siren, 105 gal. in-bed fuel tank, Kennesaw Mountain front bumper
'86 H-D Sportster - 16" apes, custom paint, custom pipes to fishtails, single fire ignition, leather saddle bags on custom brackets, bagger fender, solo seat, home made luggage rack, all LED rear lights
'66 Bronco "Big Little Monster"