Fuel sending unit ground wire

Just bought a sending unit replacement. 1967 225 V6 original. Everything lines up correctly, 6 screws, but this unit has a ground wire. The original did not. There is a center post/bolt on the top where the wire to the gauge connects. So that is obvious and goes there. When I touch the ground wire to this post the gauge reads past full. When I put the ground to one of the screws it reads empty. No instructions with this unit. Where should the ground wire connect? It should read about half since the tank is currently half full. I hope someone has done this before and can guide me. The gauge is a replacement from a few years ago and was working fine until recently.
Thank you for your help.

Peter

 

I bought my jeep as a complete rebuild and it has a new sending unit. I looked and there is a ground wire to the frame on mine. It is attached to the seat frame bolt. Hope this helps.

 

The ground wire is added by the aftermarket supplier of the sender unit. There is no ground wire on the original application. If you are using a steel tank, the sender grounds through contact with the tank, and you don't need the ground wire. If you are using a plastic aftermarket replacement tank, you need the ground wire to bridge from the sender to the body or frame of the Jeep.

Don't arbitrarily ground the sender wire. Instead take your new sender and connect the sender wire to the post and the ground wire to the Jeep body or frame, outside of the gas tank. Now the gas gauge should move up and down as you change the float position.

 

Tim, Thank you for the direction. I have the original steel tank. Because of this, should I just remove the ground wire entirely? There is a seal that goes between the ring of the sender and the tank that is made of cork. Might this not be allowing the proper ground? Maybe I should remove the seal and have it be metal on metal?? I don' see where else the sender would make contact with the metal tank?

Thank you,

Peter

 

Or....the ground wire is there because of the cork seal and should be used. If that is the case, can I ground to one of the 6 screws that hold down the sender to the tank? Or does that need to attach to a non tank area body screw?
Thank you,

Peter

 

Peter,
Here's what I would do...
The sender unit should make connection to the tank through the 6 screws, cork gasket or not. You need the cork gasket to prevent sloshing gasoline from leaking around the sender. Connect the sender ground wire to one of the screws for extra contact insurance.

Now fab up a second ground wire running from one of the sender screws to the bolt anchoring the tank mounting strap to the floor. This will insure a ground connection from the sender to the body. The tank should be insulated off the floor with some foam or rubber strips between the floor and the tank bottom to prevent squeaks and allow air space so any water can dry out in there.

Don

 

Great idea. I can even reach with the existing ground wire to a factory carpet snap bracket for the rear carpet right behind the driver seat that should be a solid ground. And running a second from the tank to the floor sounds like a good additional ground.
Thank you and I think this should do it.

Peter

 

Make sure that wherever you attach the ground that that point is clean, bare metal.

 

Originally the sender did not use a ground wire as Tim stated because the original installation of the tank was grounded by the steel fuel lines clamped to the frame and the return line (if used) at the engine. As mods were made by the owner like rubber fuel lines, the tank was no longer grounded and the fuel gauge became inop. When purchasing a new sender the float arm may not be compatible with the depth of your tank. The standard underseat tank depth is +/- 6". You will need to bend the float arm so that it is at this elevation, meaning full drop of float at 6" below the bottom of the sender mount yet still rises all the way to the top when it reaches the stop tab on the sender housing.

 

bringing this thread back from the dead - is there a way to ground the original sending unit? I'm realizing that mine might not work currently because the previous owner switched to rubber lines. I have a replacement sending unit but I'd love to see if the original works first before swapping for no real reason.

Would a self taping screw+ground wire into the top of the unit do the trick?

 

If you have the 6 screw sender, place a sta-kon under a screw and run a wire to the body.

 

I do not. It's got the lock ring.

 

I wouldn't use a self tapper. Take the sender off and do what you need on the sender with the sender removed. I'ld personally run a bolt inside out with a washer inside then a copper washer (seal) and nut outside then use a second nut for the wire.

That will allow you to move the arm with the wires connected and see a guage reading.

 

I know the gauge works, so I'm hoping to make this mod without messing up something functional too bad ha!

 

That sender with the lock ring should have came with a ground tab on the sender base for a ground wire. If the tab has been broken off then I would solder a new ground wire to the sender base. Note the tab is a flat tab.

 

I don't believe the OEM senders had a ground tab.

 

Just looked at 4 senders from different suppliers and all had ground wire supplied and all had the tab. Like said if tab was broken off you won't see it and if not real clean you won't see where it was.