The wife has a 97 4runner that the gas gauge won't read correctly. When she fills it up, it will not read full. When she knows that the fuel light should be on, it still reads almost a quarter tank, and the fuel light will not come on. Is the sending unit gone, and do I have to pull the tank to replace the unit? Thanks for any help.

Does sound like sending unit is bad. On 80's 4Runners there is an access plate to get to the sending unit/fuel pump from inside the truck. Don't know if they carried that over into the 90's trucks. Check under the rear seat and the cargo deck.

Sending unit. do a search on it in this forum.