1984 Blazer Starter problem.
 

Hi guys, I got a 1984 Blazer with a 350 Cid and automatic transmission. No ECM. (THM400 2WD)

The Blazer was basically jerryrigged from the previous owner, and I'm trying to restore as much as the wiring and proper function as I can. I got the head lights and the other lights working properly, the switch for the wipers and high beams quit working after I repaired the headlights, (I believe I know the problem there, wiring from the back lights running along the frame, I dissembled a "pack" of twisted together wires, Lt green and white wires and I have to pair them up with the correct ones.)

The problem I'm having is with so many diagrams that show different configurations, my starter will stick the gear out and spin the flywheel for less than a second. It won't continously spin it long enough for the engine to crank. I had the ignition power coming from the battery (fused @ 30 amps) and I'm not understanding what I could be missing. I haven't applied direct power to the starter to get it to turn in the vehicle, but I bench tested the starter and it stayed engaged for as long as I had power and ground with a jumper for the S terminal.

I appreciate any and all help!
TB

Jury-rigged electrical system...
... I think we had that before.

I would go and look which of the wiring diagrams is the closest match to what your truck is equipped with.
Even identify it from your option-codes and the vehicle chassis number.
Try to find the "full" service and electrical & diagnostic manuals. Rockauto usually has them on print or DVD.

From there I'd start measuring resistances and voltage drops to make sure a specific part of the wiring is sound.
Also check from the fuse box onwards. We have seen fuse holders bend under load and loose contact, relais can do the same.

Check all the wire connectors for the copper strands being copper-red and not black. The resistance of copper which has oxidized is far greater than normal.
Depending on the overall condition of the wiring a complete replacement may be required.
That said, the next I would check is all the grounding straps, including those on the aft door (if equipped) and the main leads from the battery to the starter, alternator and battery ground.