68 Mustang gas guage

I have completely replaced all the wiring and sending unit on my 68 mustang.
The fuel gauge just does not want to work correctly. Please help, I don't know
what to do next.  

verify the gauge is working...

this usually takes 2 people...

key off..     helper in car...     unplug sending unit wiring at the tank....    turn key on...   does the gauge move one way all the way...

ground the wire ...  the gauge should swing all the way the other way...

this verifies the gauge and wiring is working...   and the problem would be in the sending unit .. or the grounding of the tank or sending unit..


if you have a digital OHM meter...    set digital volt ohm meter to 200 Ohm scale..   test from the sending unit connector terminal to the sending unit tube...    usually 10 to 90 ohms ...  depending on how much fuel is in the tank...    now.. keeping the test lead on the sending unit terminal..    try to touch the other test lead to a good ground. nearby...  the reading should NOT change...    the gas tank has to be grounded for the sending unit to work properly...


if when you do the first test... unplugging the sending unit.. and the gauge does not swing one way.. and when you ground the wire the gauge swings the other way..  .. then you have another problem up in the dash or the wire..


you can also measure the sending unit resistance at the tank....   then probe the same wire at the dash board with the wire disconnected from the dash...  and you should get the same OHM reading...


please make sure the dash board is properly grounded..  

f you have a digital OHM meter...  i try to change that but its not possible to change