Gas Guage going crazy

2000 Pontiac Montana

When the gas guage gets down to about 1/4 tank it starts acting weird. It will go back up to full and then easy down to "low fuel" level. It just continues this up and down bit. It appears to work fine from full to about 1/4 tank.

Any suggestions?

I had a very similar problem but mine would go from full to empty at any time . It is a fuel sending unit in the gas tank. It cost me about $350 at the dealer

I don't know if you are in the U.S. or Canada. I do know that there is an issue with Shell gas and G.M. vehicles here in Canada, something to do with an additive that Shell puts in there fuel (so G.M. says). Of course Shell is denying any fault in this and claiming there is a problem with the fuel sensors from G.M. The General claims that Shells additive actually puts a coating on the sensors which throws the gauge out of "wack" and therefore gives false readings, especially when fuel is below 1/4 tank. I for one have decided to avoid using Shell products until this problem is clarified. I have heard this theory from a couple of mechanics and there was some discussion in the news recently about this problem.

they put sulfur in the gas and that made the guages wear out prematurely. and this could be your issue.
http://www.courier-journal.com/localnews/2004/05/20ky/A1-gas0520-7307.html

Hi guys i got the problem shell gas but apparently only on Cdn west coast my local GM dealer quote to repair CDN$ 1200 as fuel pump and sender all one unit a friend gave me paperwork to claim as part of a class action suit to shell result will give you $250 max if you have your receipts you bought there gas question do you keep old gas receipts result i dont buy shell gas and neither does my family and friends one of which has the same problem results shell loses out on customers