87 Suburban electrical (IGN) problem

[mrwhite2you]

Also posed in the 73-91 Chevrolet and GMC suburbans group... as I thought about it, this is probably relevant to anyone with an 87... Apologies in advance for the cross-post.

I recently purchased an 87 suburban in fairly good condition (texas truck). When I was looking at it, the fellow I bought it from commented that he had hooked up a Sunpro tach on it, and when he hooked it up, there was a loose wire under the dash that if bumped, would cause the truck to stumble and/or die. Well, he was right, over the weekend I was picking up a couch and hit a bump in the road, and started getting a stumble. When I pulled over and started fiddling with it, she died and wouldn't restart.

After sticking my head under the dash by the fuse panel, I found what I thought to be the culprit. There was a red wire with a crimp connector (not spade, but the one that has 2 prongs) loosely stuck in the fuse block. I played around with it and if wiggled in just the right spot, the truck would run. Now this wire is stuck in to what appears to be where a fuse would go, so when I got home I went to replace this with a fuse, but it would not go in as there is a plastic tab between the two terminals. I believe this connector is above the 20Amp ignition circuit, and below two individual wires in plastic retainers.

I have a few theories as to what is happening. first, the two terminals that I am looking at are two seperate circuits to be used for accessory connections, and one of the connections does not work. Therefore, connecting the two together completes the circuit. Or, perhaps there is a circuit breaker that is supposed to be connected there, that the previous owner removed to install this tach, and did a real mickey mouse job on it. And thirdly (long shot) this wire being connected is actually completing the circuit to the HEI allowing the truck to run.

To throw one more wrench into the system... this truck was purchased from Houston area, and has a Ravelco (sp) anti-theft unit on it, where you must insert a specific key to get the vehicle to start. This unit has been (supposedly) disabled, but I am beginning to wonder if perhaps the wiring has just been rigged behind the scenes.

When I got the truck, I didn't receive the owners manual with it, and the Haynes manual that I have does not prove to have any helpful information. I am going to try to get into our local library this weekend, but was hoping someone would be able to provide either a photo/schematic of the fuse box under the dash, and/or a wiring diagram so I can attempt to dig into this. Also, any suggestions would be greatly appreciated.

Thanks!
-Mike