Starter wiring options

[BJedi76]

1986 GMC Sierra Classic 1500 SWB 4x4

There seems to be two distinct methods for starter wiring. I cannot find anything to tell me why there is a difference. Whether it was a year thing or model are they just changed methods at a certain point.

One involves the red 4g power wire from the battery positive to the starter and a fusible linked 10g to the junction box on the firewall from the starter.

The other has a black 4g power wire Coming from the positive battery terminal along the passenger side fender well & then across the firewall to the junction box and another black 4g wire from the junction box down to the starter. But I don’t understand where the fusible link comes in on that system.

is the junction box a fuse?

which system is better?

Any educated or practical opinions would be greatly appreciated.

 

[BJedi76]

And on the second system, why is the battery power wire, black?

 

[82sbshortbed]

Mines the first example you gave. 82 short bed BBC 454.

 

[eskimomann209]

I pulled mine right off the starter to the battery. No fuse.
YOLO

 

[eskimomann209]

And on the second system, why is the battery power wire, black?

Cuz not all power wires are red!
Lesson learned early or late and hard for some.
Had a buddy ground a “black” wire once. couldn’t figure why his truck wouldn’t run.

 

[BJedi76]

I guess you just add fusible links powering the alternator & ignition switch.

has anyone had any experience with both of these types of wiring & understand why it was changed. Or when?

Was it simply an attempt to get the power wire more insulated from the exhaust manifold?

manuals are getting hard to come by for these things. All I can find is a Haynes.

 

[AKguy]

The colored diagrams found on Ebay from Texas based sellers are amazing. Another great source for manuals is Faxonautoliterature.com I have the set of original parts books and reproduction assembly manuals from them. I have my nose in them a lot.

 

[75gmck25]

The first example is what I’ve seen on all squarebody trucks. The 2nd wiring scheme was used on the newer GMT400 trucks. I’m using something similar to the newer setup on my ‘75 because the junction with multiple terminals provides a convenient power point on that side of the truck.

The junction I got at the pick and pull had several power wires on it and they each have a fusible link. I just spliced onto those wires to fuse my power feeds.

Bruce

 

[dsteelejr]

1986 GMC Sierra Classic 1500 SWB 4x4

There seems to be two distinct methods for starter wiring. I cannot find anything to tell me why there is a difference. Whether it was a year thing or model are they just changed methods at a certain point.

One involves the red 4g power wire from the battery positive to the starter and a fusible linked 10g to the junction box on the firewall from the starter.

The other has a black 4g power wire Coming from the positive battery terminal along the passenger side fender well & then across the firewall to the junction box and another black 4g wire from the junction box down to the starter. But I don’t understand where the fusible link comes in on that system.

is the junction box a fuse?

which system is better?

Any educated or practical opinions would be greatly appreciated.

Going off the wiring diagram I don't see a black wire coming off the starter to as primary power along the firewall. The 32 BLK is a 2 AWG black wire coming off the positive battery terminal going to the starter. Then you have two red wires coming off that same starter post.

1 RED-2 is a 16 AWG red wire and the other wire coming off the starter, 2 RED-2, is a 14 AWG red wire. They are "Feed, Battery - Unfused" circuits. 2 RED-2 splices and continues to the junction block to supply direct battery power to anything tied into the junction block.

Those unfused primary power wires should have fusible links. Fusible links should be 4 AWG sizes smaller than the circuit they are protecting. For example, to protect a 10 AWG wire you would use a 14 AWG fusible link.

If you haven't looked already, the wiring diagram for your truck is available in the reference library.

https://www.gmsquarebody.com/threads/1973-1991-wiring-manuals.14498/

You must be registered for see images attach

 

[Bextreme04]

1986 GMC Sierra Classic 1500 SWB 4x4

There seems to be two distinct methods for starter wiring. I cannot find anything to tell me why there is a difference. Whether it was a year thing or model are they just changed methods at a certain point.

One involves the red 4g power wire from the battery positive to the starter and a fusible linked 10g to the junction box on the firewall from the starter.

The other has a black 4g power wire Coming from the positive battery terminal along the passenger side fender well & then across the firewall to the junction box and another black 4g wire from the junction box down to the starter. But I don’t understand where the fusible link comes in on that system.

is the junction box a fuse?

which system is better?

Any educated or practical opinions would be greatly appreciated.

I have never seen a system like the second one you described... It doesn't make any sense. The 1997 K2500 Suburban I got as a donor also had option 1 with a direct 4g wire from the battery to the starter. It had a direct 10g wire from the alternator to the starter with a fusible link and a 8g wire from Battery 1 across the top of the radiator to the engine fuse block. I'll be using that wiring setup with my L-29 swap. The second option sounds like someone was having a wiring problem and half-assed it to fix their issue instead of fixing it right.