Fuel gage on 318i

[moekaz]

I have replaced my fuel pump assembly and since the fuel indicator is working intermittently.
Usably after a fill up it shows it is empty and the yellow light comes on and when eventually after the tank goes down about ¾ the gage start working again. Sometime it does not work at all.
I have tested the resistance on both units and it is around 68 ohms.
Also have changed the lever from the old assembly to the new one and still the same issues.
Any idea how this system works electrically and what could be a problem, not sure if there is ground link missing somewhere.
Thanks