87 specific (tbi) wiring questions

[BowTieJockey]

I think I have gotten all of my wiring and vacuums lines figured out on this truck. When the po took it apart he didn't cut anything but he didn't mark anything either. I can't figure it where this one wire goes. I do t have the stick motor so I don't have anything to go off of. I have a 92 blazer motor in it now. And can't figure out this one wire. It's on the drivers side and comes out of the harness an out 6 inches from the bulkhead connector. I have a feeling that it's for a temp sensor in the head. There is a two wire sensor there from the 92 blazer but I have no clue what the wire is there for. Can any of you guys help me. I can't seem to find this wire on any of our carbureted trucks so I assume it's a tbi only thing.

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[Georgeb]

That looks like the temp sensor wire for the guage. It would connect to a sensor in the head between cylinder 1 and cylinder 3 exhaust ports on the left head.

 

[chengny]

From what is visible in the images that is certainly the sensing lead for the dash mounted coolant temperature indicator.

A couple of things give it away:

1. That is the only dark green wire in that area

2. It has that characteristic bent/twisted shape that comes from years of laying on the hot cylinder head

3. The connector on the end is the type that clips on to the sender in the perpendicular plane. That application (temp sender lead) is the only place I have ever seen it used. The sensing lead for a high coolant temperature idiot light is the normal (i.e. parallel to the sender body) kind.

Some pictures to assure you:

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I got to ask though, how are monitoring your coolant temp?

 

[BowTieJockey]

Not even done building the truck so there is no coolant even in it right now. I've only ran it long enough to time it. I will most likely run an aftermarket one too so I can monitor it better but I want the factory to work like it's intended to.

I thought that's what it was for but I wasn't sure. I knew that the fuel injection trucks usually had two (one for ecm and the other for the gauge).ill head to the parts store tomorrow after work. Thank you so much for the help.

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