23 gallon gas tank wiring question

[Heus33]

I have the 23 gallon tank put in by the previous owner, but I’m confused on the wiring. I have a carburetor. There’s only one wire coming out of the sending unit, a small black wire which I’m assuming just goes to ground.

But I also have what looks like the old sending unit wire laying here. see photo attached.

Do I need this old sending unit wire? If not, how do I get the fuel gauge to work?

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[Bitch'nBronco]

The one wire is a negative sender wire to the gauge, it doesn't get a positive unless there is a fuel pump. I'm not sure what that connector is, my 23 gallon tank took a ring terminal to a post with a nut.

 

[Heus33]

I found the actual sending unit plug.

So this brings up two questions now

1. What is that first wire for?
2. How do I connect the stock sending unit plugged to the new sending unit? It just has one post with the ground wire coming off of it.


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[Heus33]

I found this which seems to suggest to cut off the old plug and wire it in.

https://classicbroncos.com/24galtank.shtml

 

[Heus33]

Does the yellow wire from the stock wiring get cut and connected to the middle post on the sending unit?

Is there an additional ground wire needed?

 

[Oldtimer]

Looking at photos in Jon's product review, I would connect yellow (might be orange) wire from the
stock harness to the center terminal on sender mounting plate AND run a ground wire (black) from
one of the perimeter screws for mounting plate to a ground point on frame.

 

[Heus33]

Looking at photos in Jon's product review, I would connect yellow (might be orange) wire from the
stock harness to the center terminal on sender mounting plate AND run a ground wire (black) from
one of the perimeter screws for mounting plate to a ground point on frame.

View attachment 940821
View attachment 940822

This is my thought as well. But what happens to the ground wire on the stock harness? Perhaps I just need to test it and see where we end up.

 

[Oldtimer]

The ground wire in stock harness in my 68 Bronco goes a foot or so and is attached to frame with a screw.
In fact it is the only stock ground wire between body and frame in the Bronco.

 

[Heus33]

The ground wire in stock harness in my 68 Bronco goes a foot or so and is attached to frame with a screw.
In fact it is the only stock ground wire between body and frame in the Bronco.

Got it! I connected the orange wire from the stock sending unit to the post on the new sending unit, then used the stock ground wire and connected that to one of the screws that held down the sending unit.

Thanks for your help!