87 Nissan SE-V6 Starter Problems

[craftsman don]

Hi Everyone,
I am a new member and I hope someone can help me with this problem I have been having with my 87 Nissan 4x4. I have checked the archives and I have seen several problems of this nature, but no solutions. The starter has been giving me problems for over a year and now it finally will not start at all, unless I drift it off. I have replaced the battery, ignition switch, starter (Auto Zone), and checked every relay and switch that I can think of. I have tried using a couple manuals (Haynes, other) to trouble shoot the wiring, but not enough detail. I am getting voltage to the large wire going to the solenoid (black/pink stripe) when I turn the switch, but nothing to the smaller wire (black/yellow stripe). The starter battery cable is fine. At first I thought Auto Zone sold me a dead starter, but he tested it in front of me, but could not explain why he connected power to the smaller wire going to the solenoid. I do not know what this smaller wire does, I do know it goes back to the ECU (and possible other areas but cannot find in schematic) and think maybe the ECU has some control over the starter system. Maybe the ECU is not allowing the starter to function because of another sensor or relay issue. Any help is greatly appreciated, even if someone could explain what this one wire does going to the solenoid, I have seen some posts call it a solenoid kicker.

thanks,
Craftsman Don