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Wiring LS for standalone

Chkn

What Knockers
Joined
May 19, 2020
Member Number
145
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Question for the brain trust.

Working on wiring the LS (GEN IV) in my FJ80. Should probably make a thread for it :homer: but.... How conservative are the OE ratings for the wiring systems on an LS engine? The reason I ask is because I need to find a power distribution block / fuse block to power the new drivetrain. When looking for DIY/pre-wired solutions there is not a whole lot that gives me the warm and fuzzies in the price point I want to pay. :lmao:

When viewing the factory wiring diagram there are ~4 different circuit types to run the Engine and Trans.

1. B+
feeds these fuses:​
  • TCM BATT + (10A)
  • ECM BATT + (10A)

2. Run/Crank Relay
feeds these fuses:​
  • Trans IG1 (15A)
  • ECM IGN (15A)

3. Powertrain Relay
feeds these fuses:​
  • Eng (15A)
  • O2-A (10A)
  • O2-B (10A)
  • Inj A (20A)
  • Inj B (20A)
  • ECM throttle (15A)

4. Fuel Pump Relay
feeds this fuse:​
  • Fuel Pump (20A)

Looking at the interwebs that is not amazon there are:
1703108301461.png

1703108344903.png


2 relays and 6 fuses which are rated below the factory diagram.

So I am leaning towards wiring a Bussmann RTMR to get the adequate number of relays / fuses with the correct ratings. Maybe I am overthinking this (like always) but would like some input from smarter people than me, or at least from people that haven't burned an LS swap to the ground.:flipoff2:
 
 
So I am leaning towards wiring a Bussmann RTMR to get the adequate number of relays / fuses with the correct ratings. Maybe I am overthinking this (like always) but would like some input from smarter people than me, or at least from people that haven't burned an LS swap to the ground.:flipoff2:
Aftermarket has it figured out.
You're overthinking it.
 
Aftermarket has it figured out.
You're overthinking it.
That’s what I wanted to hear 🤣. Still surprises me that GM was so conservative with the fuse/relay ratings.
 
Majority of aftermarket harnesses are 4 fuses and 2 relays...

My stock harness was done following LS1tech 4 fuses and 2 relays.

Nothing's burnt down and haven't blown a fuse...
 
I'd also wager the ones from MM and other shops come out of the same factory as the ones from ebay/amazon.

I'm going ebay harness which has the ebay fuse block. 8 billion people have used them for swaps, i'm sure it'll be fine for mine
 
I'd also wager the ones from MM and other shops come out of the same factory as the ones from ebay/amazon.

I'm going ebay harness which has the ebay fuse block. 8 billion people have used them for swaps, i'm sure it'll be fine for mine
I ended up getting the current performance one. It is good quality. If I remember I’ll get a picture of it when I get home.
 
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