Ok so now my 2005 g35 started to have this issue with the fuel gauge. I filled it all the way up the other day and It only went past the middle bar by just a tiny bit. And sometimes it goes all the way to empty and just rises back up again. What could be causing this problem?

 

Mine's doing the same thing every now and then. I just monitor by my driving habits and fill up when the hand its just below the 1/4 mark.

 

It's either the cluster or the fuel sender units. You can do a test of the cluster if you search the FSM and some people use q-tips to clean the fuel sender units. My car has this problem as well and I've ran out of gas a few times, lol. If none of those work you have to replace the sender units or the whole assembly depending who you talk to.

 

The easy/cheap fix is cleaning contacts on the fuel sending unit under the rear seats. Fixed my problems.

 

I tried everything on the forums (cleaning sending units with Qtips), fuses, etc. The only fix was to send it to these guys on ebay: https://www.ebay.com/itm/INFINITI-G3...ia5:rk:15:pf:0

Fixed it and havent had a problem with it since.