Fuel gauge not working

[shortbus]

i just got this jeep, i traded my DD 1986 cadillac fleetwood for it.
its cool it just has some issues. the original fuel gauge is missing the needle.
so i hooked up my room mates autometer as a loaner. but the thing only reads 1/4 and bounces around when driving, i know its not right as i have filled it up with the same 1/4 tank reading. i checked the pink wire witch is now blue and the ground is still conected to the frame. i hooked power to a togel switch just to weed out posseble wiring issues. the wireing in this thing is compleatly trashed an needs to be replace but will have to wait till my job starts back up this spring, i just need to get this fuel gauge working so i dont have to worry if im going to stall or not. im broke as a joke on unemployment
so im not trying to put gas in the thing every time i need to go some place.
Pleas help, im at my wits end. thanks.
oh and the sending unit is new. the jeep is a 1980 CJ7 AMC 258 i6 / 4.2l

 

[BusaDave9]

Put an ohm meter on the wire going back to the sending unit. You should have 73 ohms when you are out of gas. You should have 10 ohms when you are full.
You say the sending unit is new but a short or open in the wire could also cause the readings to be incorrect.

EDIT: I think a bad ground is most likely.

 

[Old Dog]

is the fuel gauge the same as the sending unit ie. 73-10 ohm? if not it won't read right.
if your new sending unit is made by omix-ada I would check it with an ohm meter to be sure it's good. (most of their china junk doesn't work from the get go)

 

[BusaDave9]

Check out this link: http://home.roadrunner.com/~john.strenk/Gauge%20web%20page/basic_troubleshooting_for_cj_gau.htm

 

[shortbus]

is the fuel gauge the same as the sending unit ie. 73-10 ohm? if not it won't read right.
if your new sending unit is made by omix-ada I would check it with an ohm meter to be sure it's good. (most of their china junk doesn't work from the get go)

I dont know, the gauge came out of a chevy im not sure of the ohms on it..
maby ill drop the tank when it runs out and heck the sender.

 

[BusaDave9]

I dont know, the gauge came out of a chevy

There's your problem. Many Ford gauges would work. Not chevy

 

[BusaDave9]

I have an AutoMeter gauge for sale that would work.
For Sale - Autometer 3315 Fuel Level Gauge - Jeep-CJ Forums

 

[shortbus]

how much shipped to ma?...

 

[BusaDave9]

how much shipped to ma?...

I PMed you the details.