Help! electrical problem, fuel guage

need some help please with 98 Z-71.. I am having a tough time with this one.
Fuel guage is acting erractic. When you turn on the key it swings wildly. then settles out, when you crank it it does the same thing. swings toward the full side then back to normal level. Then with the truck running, it pulsates a small amount...Like it's quivering.. And to top that off, if you turn on the cruise control it still pulses, However if you set a speed and actually engage the cruise control it begins moving erractically quarter scale or so...Give me your thoughts. Is there a common ground between the cruise and fuel guage. I think I have a weak ground? but where to look??

Check ground at fuel tank-clean connections and see if that helps.

Thanks, but where is the ground at the tank. If I am not mistaken the tank is plastic which means there is a ground wire attached on the top of the sending unit but where does that attach to the frame or body?

there is a thread that talks about this. basically i have the same problem. the dealer told me that the actual fuel gauge is bad, but the gauge is not serviceable. you have to have gm send you a whole new instr cluster for 400$. due to the fact the odometer is in the cluster GM regulates this part. search term "fuzzy fuel gauge"

Good luck- if you figure out something other than this let me know