New Fuel Gauge and Fuel Sending Unit, are still not showing any readings?

[1985 Century Mustang]

I'm banging my head here. I replaced a new sending unit (Moeller same ohms as the medallion unit) and a new (Sierra) fuel gauge dame connections as my old one, and I'm still not getting any gauge reading. There is voltage to all the legs on the gauge, even the sending unit in the gauge is showing voltage. What do I check now. Maybe a bad ground on the tank itself? There's voltage to the positive wire to the sending unit also. Also my trim motor gauge isn't showing any levels either.

Further: The two gauges (The Fuel and Trim,) on the top of my panel both aren't functioning oddly, and the two directly below on the panel are. The Volts and Temp Gauge.

 

[mike_i]

Why are you replacing the fuel gauge and sender? If you were having a problem with them what was the problem? Have you confirmed the fuel tank is grounded? When you measured 12v on the sender where did you have the neg lead? Did you have it on the tank, that's if it's a metal tank?

 

[1985 Century Mustang]

Why are you replacing the fuel gauge and sender? If you were having a problem with them what was the problem? Have you confirmed the fuel tank is grounded? When you measured 12v on the sender where did you have the neg lead? Did you have it on the tank, that's if it's a metal tank?

Answers to your questions.
Yes tank is metal and grounded.
Both gauges did not function and or give any readings.

I thought that one or the other was bad, so I bought both as they were inexpensive. Now I think it can be a bad ground,,, which I'm going to do today, is run a ground from the gauge straight to the battery, and see what happens.

 

[Scott Danforth]

did you do any troubleshooting prior to throwing money at parts?

5 minutes with a jumper wire and DVM would have indicated what is wrong with the original. most likely the ground buss at the helm has corrosion

 

[Chris1956]

Gee, If both components are new, the wiring is the likely suspect.

The ground on the gauge and the sender needs to be common and not have any resistance between them.

The gauge also gets +12VDC and the sender wire. A lot of senders have their own ground lug. Since there is a gasket between them and the tank, and some sender screws have plastic washers. A tank ground may not make a good connection to the sender.