Engine Bay Wiring

[firebane]

So I'm trying to wrap my head around the wiring under the hood of my truck and have look at a few wiring diagrams but nothing is making sense. I think I have a general idea of how the wiring is supposed to be but what is in the truck doesn't jive. I don't know squat about previous history of my truck so I'm trying to ensure that while I'm doing the work that I am I can put it back together better.

So here is what I think I understand and where I will need some clarification. My truck is currently a 1974 with a 350 under the hood.

1) (-) of battery to alternator bracket
2) (+) of battery to starter
3) Red wire from back of alternator to (+) on battery
4) Purple wire from igition to starter

Am I missing anything? How does power get to the junction block under the hood of the truck? It looks like that comes from the starter?

How many wires are supposed to be attached to the starter?

I'm sure I'll have more questions but for now that is it.

 

[scottybaccus]

You are seeing it right. That's not exactly best practice these days, but it's how it was done.

Take note of how many ground wires you find connecting the major metal parts. They should connect: core support to frame, cab to engine, frame to engine, battery (-) to frame, (-) to engine (you mentioned the alternator bracket), etc... There are more, bed to frame, fuel tank to frame, cab to frame...

The ground plane is really important. Without wires connecting all these things, the negative side of most every circuit is going through paint, rust, rubber mounts, etc. Now factor in that everything moves.. Grounds should be the first thing checked with any electrical problems.

 

[firebane]

Yeah I know about the grounds and such and that will be next.

But I'm still curious on how the junction block gets power? From the battery? Starter? it has to get it from somewhere?

Should there be any fusible links anywhere?

 

[robert8096]

Most of the time the junction block gets power from where the battery wire connects to the starter. Wire from the large lug on the starter to one side of junction block. This should be a wire with a built-in fuseable link

 

[firebane]

Most of the time the junction block gets power from where the battery wire connects to the starter. Wire from the large lug on the starter to one side of junction block. This should be a wire with a built-in fuseable link

AH! I am 99% sure that wire is missing LOL.

 

[Quadrajet Power]

You have the main power cable that goes from the battery to the starter. The main engine wiring harness should have a heavy wire that is on the main starter terminal with the battery cable, and that feeds to your main fuse block. It should have a fusable link just a few inches from the starter.

 

[firebane]

You have the main power cable that goes from the battery to the starter. The main engine wiring harness should have a heavy wire that is on the main starter terminal with the battery cable, and that feeds to your main fuse block. It should have a fusable link just a few inches from the starter.

Starter should have 3 wires from what I understand.. 1 to the (+) on the battery, 1 with a fusibile link to the junction block and another with a fusible link to the bat terminal on the alternator.

My truck.. had zero of these I love POs

 

[Quadrajet Power]

I changed my cars up so they only have one wire at the starter, and I use a remote solenoid. Alternator feeds a junction block on the firewall. From there, it goes to battery and the main line to fuse block also connects.

There are some options, so somebody may have done something like that.