i have a 1999 dodge grand caravan. about 6 months ago, the fuel gague started to work incorrectly. when it shows 1/4 tank, it is actually about empty. i've run out of gas a few times because the "dummy" light never comes on any longer to give me 30 miles warning. when i fill the tank, it goes back up to display full, and it gradually decreases until it displays 1/4 tank, and then it's really empty.
any ideas on what could be the trouble with this would be most appreciated.