Fuel sending unit ????

Had to buy a new gas tank for the CJ5 so I got new sending unit with it and I had to buy new speedometer unit cause the temp and fuel gauge were not working. Put the tank in a while back but the fuel gauge still would not work so yesterday put the new speedo unit in and hooked everything up. The temp gauge works now but soon as I turn the key on the fuel gauge goes to past full. I think I have a bad new sending unit cause if I put a meter on the sending unit that is in the tank it goes to ground. I checked the old sending unit in the original tank and it does not does this if I put a meter on it. Now if it is good I don't know. I am going to take the one out of the old tank and put in the new tank and see if it works. Is there a way to check the sending unit with a ohm meter to see it it is good.

 

Put one lead of your ohm meter on the wire connection post and the other to ground (the body of the sending unit). Move the sending unit arm carefully through it's range of motion and check the readings. They should change steadily and evenly as you move the arm.The sending unit works on a grounding circuit, i.e there is not 12 volts flowing through it.

 

I took the sending unit out of the original tank checked it with a ohm meter and it showed that it was working. Put it in the new tank I bought and the fuel gauge works now. I check the new sending unit that I bought with a ohm meter and it shows it to be working but I remember the ohm readings were different than what the original sending unit had. Don't remember what they were should of wrote them down :? but it is working for now. Thanks for the help.