Starter relay replacement

Replaced the starter relay on my son's '84 Ranger (2wd, 2.8 V6, manual trans) with one I picked up at Autozone. Thought I was careful to put all of the wires back in the positions they were before but was a bit thrown off by the new relay having 4 posts vs. the original three. Truck started fine several times with no issues. I go to work, my son starts his truck, and now the starter solenoid will not disengage when the truck starts (necessitating the removal of the positive battery terminal from the battery to break the circuit).

I'm feeling like a bit of a dumbass right now. Looked in my Chilton's manual for the truck and it shows only the most basic of diagrams to the circuit. I have two fused links (one orange 16 ga., and one red 18 ga.) on the same post as the positive lead, a black wire (about 18 ga) and the black lead to the starter on the other post (the post closest to the cab), and a push-on red lead on the left front post (the post is much smaller than the two copper posts). The small post on the right front of the relay is empty. Have I mis-wired something? I'm including a pic of the new relay from the bottom so everyone can see the posts as they are configured. The two small posts on the front of the relay each have the letters S and I stamped above them, left to right. Any help would be appreciated. I want to get my son's truck back on the road so I can have my Expedition back again! Thanks in advance, ---rick:confused: