"
There's alwaysvonly been the 2 wires"
I
think this refers to the quantity of red wires - not the total number of wires connected to the starter/solenoid assembly.
But somebody might have made some "upgrades" to the OEM wiring. The primary section of the start/charge wiring group on these trucks differs a bit from the earlier C/K versions:
Instead of the usual 4 leads connected like this:
1. One (1) large diameter black (from battery) - connected to the "B" terminal
2. Two (2) medium diameter reds (to alternator and system) - both together and also on the "B" terminal
3. One (1) purple (from ignition switch) connected at the "S" terminal
The 1990 V series has only 3 leads connected to the starter/solenoid assembly. It is basically the same set-up. The way they eliminated the 4th lead was simply by combining the two reds into one common wire that runs straight up to the firewall junction block. This common lead feeding the JB is protected by a fusible link. The feed from the JB to the ignition switch is also protected by a fusible link.
I only have the schematics to go by, so I can't see where the fusible links are physically located, but an FL is always inserted at a point in the circuit that is closest to the power supply. This protects the feed wire as well as the circuit. So it can be assumed that the FL is right down close to the "B" terminal on the starter.
On a 1990 V series truck, as factory - the connections at the S/S assembly are:
1. One (1) large diameter black (from battery) - connected at the "B" terminal
2. One medium diameter red (to firewall JB)- also connected at the "B" terminal
3. One small diameter purple (from ignition switch) connected at the "S"
So it is possible that - if somebody spliced the primary supply from the battery (black) and the feed to the JB (red) together - it would appear to be only one wire (a red one). Since the OP mentions that there is a fusible link visible on the battery feed that would make sense.
As for the other "red" wire, it might be that the actual color is the standard purple and it just has developed a "patina" over the years.
Having said all that, I have no idea why the starter motor isn't cranking.
There is nothing unusual about this starting circuit:
If the battery is fully charged and the cable to the "B" terminal is good (and the connections at both ends are tight/clean) - that takes care of power supply.
If the starter/solenoid is known good and bolted securely to the block - that covers the component
If there is 12VDC at the purple wire with the ignition switch in the "START" position - that proves the control circuit is okay.
The only remaining part of the starter motor circuit is the path back to the battery negative. That would be the ground cable that connects to negative post to the engine block.
If the headlights, etc (they have an independent ground circuit on the radiator support) are working and the purple lead to the solenoid shows 12VDC in START - take a good look at the main ground cable. As a test, just use a jumper cable. Clamp one end to the battery negative and the other to a good clean ground on the engine block and try cranking.
The start/charge wiring diagram for a 1990 V with a gas engine;
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