Mystery wire help...

Finally putting the tbi on my '87, and am changing the harness with one I know is good. The ecm1 fuse blew the last time it was running, and not knowing the cause, I'm changing the harness, injectors, ECM and other pieces with known good ones from a near identical parts truck i had.

First, I was wanting to know what this wire is, and where it goes, as the connector was missing off of it on my old harness Attachment 3382


Another question, the ground connector that comes out of the right rear of the harness, how important is it? In changing harnesses I realized my old harness did not have this ground anymore, only parts of the wires were left and it was not hooked up. Just wondering if this could have been the cause of some of my previous problems.

I have ordered the moates auto prom and the g2 adaptor - should be here by next week. Just wondering if there are modified bins for a 400 small block that would be a good staring point for tuning. I'm running a 406ci sbc, 8.5:1 c/r and stock cam afaik. Th400 trans, 3.73 gears.

Thanks guys, this has got to be the best tuning site on he web!!!

The connector looks like it goes to the oil pressure sender unit that would be at the rear of the engine. The sender is a switch that supplies the ground side for the oil pressure dash light. Not sure exactly where the ground wire connects, but I see them on the rear of the cylinder heads, bellhousing bolts, and intake bolts.

Thanks. My old harness didn't have the factory connector on it.

Ok, here's another. Coming out of the left side of the harness, a long red wire with a fusible link in it. Roughly a 14ga wire I'd say...

Thinking it goes to the alternator? But on my truck the alternator goes right to the positive cable on the battery. Just tape it off and ignore it?

Thanks.

Sure it does not go to the power distribution block on firewall? See if it comes from starter?

I think there is a junction block on the right side of the firewall as seen from the drivers seat. Should be a plastic cover over it.

If my Suburban wasn't buried in snow I'd look for you... pretty packed in as it has not been moved since the snow falls...

I've got the one that goes to he started hooked up. This wire seems way too long to go to the power distribution block, otherwise that's where I'd've put it... If I stretch it out straight it reaches to the radiator... That's why I thing maybe it went to the alternator...

Hope to have it at least crudely running tomorrow... See how it goes. Thanks for all the help guys, this site is the greatest!

Well, just looked back at some pictures I took of the parts truck before it disassembled it and it isn't the alternator wire ...
But it did have a lot of unusual wires... So not sure what it is/was. Will tape it up and ignore it for now... See if I remember what it was.

Dual batterey wire? Brake controller wire? Trailer power wire?

If it's that big a power wire you should know what the other end is hooked too?

Aha!!! Dual battery wire... The parts truck had dual batteries! That must be what it is.