Harness hookup

[jackyl9999]

Im getting in the final stages of my swap, I have got my harness on, and am in the process of hooking everything to start it for the first time. I have a couple of dumb questions. I would rather this be successful than end in a fire.


Where is the best place to wire in the Keyed 12v and Constant 12v hookups on my reworked harness?


How does the ignition key connect with the starter? Is it thru the Keyed 12v wire and the cpu?

Dumb questions I know, but I have no idea what I am doing on electrical setups.

[ls1nova71]

The key on 12v to the ignition relay should be hooked up to the wire that originally went to the coil. At the bulkhead you would need to find that wire and change the wire to a regular tsince the original is probably a resistance wire. The constant hots can be hooked directly to the battery, or junction block usually on the fender. This is assuming your new fuse block is under the hood. If youre keeping it inside, you can hook the ignition to the back of the ignition switch itself, there should be constant hots there too.

The starter stays the same as your original engine, purple wire from ignition switch to the neutral safety switch and then to the starter.

[jackyl9999]

My truck has a Painless wiring harness. It used a HEI distributor in the old engine. Would the key wire go to the old distributor hookup?

[ls1nova71]

Yes, that is the wire that stays hot while cranking.

[aknovaman]

FYi. Jack if the engine runs bad, check for obd codes then verify all the PCM wires are in the correct pcm connector position. I have repaired 4 of the painless harnesses with pins in wrong positions.

[jackyl9999]

My chassis harness is a painless. The engine harness is a reworked OE.

[aknovaman]

Thank God for that.

I work with 4 different street rod shops building harnesses and tuning EFI. Early on they used painless, but no more EFI harnesses from them. Same with Street and performance. too many bad apples.

[jackyl9999]

Another question. Does this pigtail coming off my positive battery terminal have any use?

If not do you just cut it off and wrap in tape?

[ls1nova71]

It went to the original under hood fuse box, if you are getting your power for it somewhere else then you dont need it.

[jackyl9999]

Thanks for the answers guys. Got it running last night. Fired right up.

[jackyl9999]

My harness has a relay for the fan, but it has no wire for the power supply. I have a jeep electric fan. It uses a purple and a black wire. What would be the best way to wire this fan to my ECM/harness?

[Hart_Rod]

Originally Posted by jackyl9999

My harness has a relay for the fan, but it has no wire for the power supply. I have a jeep electric fan. It uses a purple and a black wire. What would be the best way to wire this fan to my ECM/harness?

Your picture isn't very clear. If your harness has a fan relay, one of the 4 wires should be an output from the relay that you should connect to the purple wire on your fan and the black wire from the fan should go to ground.