Unknown Ground Wire Location

[Torq_Shep]

I have a disconnected ring terminal that looks like a fat ground wire near the ignition coil on my truck. Does anyone know what I am supposed to have this connected to? I am assuming it is an engine ground but I really have no idea. 

 

[pizzaman09]

First I'd confirm it's ground by checking against the battery negative terminal.

 

Does it look like it's supposed to reach the common ground near the dipstick?

[Torq_Shep]

5 hours ago, pizzaman09 said:

First I'd confirm it's ground by checking against the battery negative terminal.

 

Does it look like it's supposed to reach the common ground near the dipstick?

It does not have continuity to ground but when I found it, it was physically touching the engine block. It is definitely not long enough to reach the common ground next to the dipstick but it appears to be coming out of the same bundle of wires that the ignition coil trigger is connected to. 

[Gojira94]

OPSU have a wire on it? Looks eerily

similar and in about the right place…

[gogmorgo]

Might be one going to the alternator? Otherwise not a lot in that spot to connect to.

My ‘91 4.0 has the oil pressure sending unit wire in loom with the starter trigger wire and it’s not a ring terminal. 
I don’t see anything that looks exactly like that on mine. I do have a ring terminal on what looks to be an alternator ground bolted down to a coil mount stud but it’s thicker than that one looks, 6awg maybe, roughly the same diameter as a spark plug wire.

The field wires off the alt are roughly that size, although normally they’re encapsulated in that plastic block that holds all the alt wires, unless that’s gone missing.

For me that bundle has the ignition coil wires, a/c clutch, alt, and starter trigger and oil pressure that run way further back past the oil filter. Only ones with ring terminals are the two alternator field wires, black and green, and then the big alternator ground, all of which have the black plastic block holding them together, and I think you’d have charging problems or a Code 41 if any of them were disconnected.

[Torq_Shep]

5 hours ago, gogmorgo said:

Might be one going to the alternator? Otherwise not a lot in that spot to connect to.

My ‘91 4.0 has the oil pressure sending unit wire in loom with the starter trigger wire and it’s not a ring terminal. 
I don’t see anything that looks exactly like that on mine. I do have a ring terminal on what looks to be an alternator ground bolted down to a coil mount stud but it’s thicker than that one looks, 6awg maybe, roughly the same diameter as a spark plug wire.

The field wires off the alt are roughly that size, although normally they’re encapsulated in that plastic block that holds all the alt wires, unless that’s gone missing.

For me that bundle has the ignition coil wires, a/c clutch, alt, and starter trigger and oil pressure that run way further back past the oil filter. Only ones with ring terminals are the two alternator field wires, black and green, and then the big alternator ground, all of which have the black plastic block holding them together, and I think you’d have charging problems or a Code 41 if any of them were disconnected.

I will look closer. The big one that is connected to the coil pack bolt is present but this one is close enough to the alternator that it could be an alternator ground. I think it is has an aftermarket alternator on it so maybe that wire wasn't needed? 

 

As far as charging, it seems to do alright, sometimes I am closer to 13.5 than to 14 if I am running all of the fans but other than that it is right in line. 

[Torq_Shep]

I looked everywhere, everything seems connected and I am not having any electrical issues that I think could be linked to this... Maybe I will figure it out someday but I am just not going to worry about it. 

 

It is definitely not OPSU or primary ground to block for certain. It could be something to do with the coil or a leftover from the alternator.