Wiring help needed

[Blake_H]

Well, I have finally progressed to the point of putting the truck back together. I now only have the wiring left to do. But, I have run into a problem. My ecm and harness for the new 8.1 are great. It's labeled and I have no questions there. But on the harness for the old 454, that's where I'm having a heck of a time. I can't figure out what wires I need to use, and which ones to cap and hide. I have spent many hours searching through build threads to see if I could find the answers, but with no success. I didn't think this would be this difficult.

This is my original engine harness from my 1986 crew cab, 2wd truck.


Hard to tell in the photo, but it is hammered. The truck started life as a California smog truck with the massive spaghetti of vacuum lines. It did not have electronic spark control on it.



I have the GM 10-30 Series 1986 Light Duty Truck Wiring Diagrams number ST-330-86 WD and I have a Chiltons Full Size Trucks 1980-87 Repair Manual #28622. In the GM manual I have 2 choices. One is the light duty V8 truck diagram and the second is a heavy duty V8 truck diagram. Neither of which match up to my fuse block connector/harness that came from the truck. My harness has to many wires to match the heavy duty, and not enough to match the light duty.


Both 1986 diagrams in the Chiltons manual show an engine control module and the wiring coming from it. Neither apply to my harness, I think, since I don't have an original ecm. So, I gave up on my original and retrieved a harness that I had gotten from a truck at the local 'you do all the work' yard from the garage and started to look at it.


This came from a 1986 3/4 heavy duty truck. It had all the smog stuff on it as well, and is in much better shape than the original harness. But, none of the diagrams from either book match it as well. Also, this harness has a few more wires to it than my original, so I'm not sure it will work.

Some questions that I have.
What do I do with the alternator? On the original truck I had a wire from the battery to it and a wire to the starter all on a post on the back. Then there was a connector with 2 wires in it. My new alternator doesn't have that, it just has the post. I am thinking that the battery/starter wires stay, but what about the connector? Is that for the gauge in the cluster? If it is, how do I integrate that with the new alternator?

Oil pressure is handled with the tan wire from truck to tan wire that plugs into a sensor in back of the manifold, on the block. Correct?

Water temp comes from the ecm to the green wire that was on the driver's side cylinder head. Correct?

I figured out which wire was for the sending unit, pink'ish/orange wire that I traced back to the tanks and got that handled. That really is the only one I have figured out.

So, that leaves me with all the rest, and I have no idea what to do. I am so lost on this, and could really use some help.