Ground wires ?

[Layne02]

Hi everyone, I am putting wiring back on motor after rebuild, I labeled most everything but did find what looks like two wire tied together that have a ground eyelet terminal but I am not sure if thats what they are. They are off of the group of wites that go to starter but more at top of motor , like they may ground to maybe rear bolt on intake. Anybody know the wires I am talking about? I dont see what else they could be.

 

[jetman]

Likely a ground. But could be something else.
I would get a multimeter and verify that said eyelet wire is connected to the balance of your known negative wiring. If in doubt, I think there is a wiring diagram w/ wire colours annotated somewhere on this site.

 

[Jarhead79]

Snap a pic that might help us

 

[chengny]

Is one wire tan and the other blk/wht? If so, they should be connected to a good ground point on the engine block/head.

Looking at the dwgs for your engine compartment, there is only one ring terminal with a two wire splice - that I can see. The wires are tan and blk/wht and the ring terminal is shown as grounded to the engine.

The tan lead is the reference ground from the O2 sensor.

The blk/wht is the 450 circuit. It is a common ground for a bunch of engine management components. For example: the EVRV solenoid, FPR, ESC, speed sensor, fuel module, etc. It is also the primary ground for the ECM itself.

Here is one page of the 450 circuit:

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So, if these are the wires you are asking about, don't forget to connect them to ground (especially the blk/wht 450) - or you won't go anywhere.

 

[Layne02]

One is black with white stripe, other is brown , kind of a darker brown than a tan

 

[chengny]

One is black with white stripe, other is brown , kind of a darker brown than a tan


I'm LMAO because I'm severely red/green color deficient - I can only reliably discern the colors blue and yellow. Everything else is pretty much a grayish beige color. Oh yeah, I can see black, white and silver.

Anyway, trust me - those are the wires that are discussed above. When I say blk/wht that means a black wire with a white tracer (or stripe as you say).

As far as the brown lead; when he was just a little wire living and in the GM assembly plant, he was probably a lighter tan color. But, after 30 years, he's going to look older. It's inevitable that living your entire life in an engine compartment is going to take it's toll.

Seriously, exposure to the elements under the hood (heat/grime/exhaust fumes etc.) will cause any wiring insulation to become darker over time. I bet if you traced the tan - now brown - lead back into the cab, where none of those elements are present, you'd find that it is still tan and clean.


If you want to be sure, unplug the harness connector from the ECM (pull the bigger of the two plugs). Find the 413 tan lead where it connects at row D pin 6. Connect your meter with one probe to a good ground and the other to the 413 tan pin at D-6. Set the meter to continuity (audible feature). Go into the engine compartment where the mystery double wire terminal is.

Touch the common ring terminal to a good clean spot on the engine. If the tan wire (the O2 reference leg ground) at D-6 is the same one that is connected to the ring terminal, the meter will beep when the ring terminal is grounded. If it doesn't beep, I'm wrong and you will have to keep looking.

 

[Layne02]

Ok great. I was already pretty sure they were ground but wanted to doible check. The eyelet has that kinda star pattern on it like a ground terminal has, plus theres nothing else back there to power . Thanks

 

[yevgenievich]

they are usually bolted to the back of the head