[midniteblues]

From my experience.

If the pump is the oe pump then it may be on its way out,the sending unit getting sloppy and giving wack readings is a early indicator of it.

If the pump and module have been replaced then it's normal for the sending unit not too work
Aftermarket modules the sending unit part don't seem to last or work very long.
It seems the piviot point for the float gets real sloppy in short time and the two halves of the rheostat loses contact with each other. Some bounce around on the pivot with sloshing gas and that's why you get a bouncy needle.

From what I have read online.
If your pump goes out its best to just replace the motor and not the whole module,as the oe modules have a much better fit on the pivot point on the body. Some lose contact over time some dont.

5 yrs ago I put a new airtex module and pump in my z and learned afterwards that replaceing just the pump motor is
the way to go.

With my new airtex module the gas guage only worked for about three months after.
Dropping the tank or pulling the bed is too much work too remove and play with the module.
I've been using the tripometer as a guide and usually only fill the tank till the pump clicks off the first time.