[1iwilly]

hello to all
i'm having a fuel gauge isue since i bout this 97 awd ls in feb-09
when i start the van lets say the gas gauge read 3/4 of a tank by the time i drive about a mile or so the gauge moves to 1 line before 3/4 by the time i have gotten over 10 miles it has move to 2 lines before 3/4 but if i turn the van off then turn it back on it would show the actual true reading which should. like the other day i had 1 line before the red empty line
i drove to gas station when i fill it up it only took 18.54.9 gallons on a 25 gallon tank.the weird thing is if i had 6 gallons left
and i'm suppose to get 14 to 15 miles to the gallon 6x15=90 or 6x14=84 i definite know there is no way i could of drove that many miles on 1 line before empty.

 

[xequar]

GM's never really been all that great at gas gauges...

 

[1iwilly]

also i forgot to ask isn't the check gauges like suppose to come when the fuel gets realy low???

 

[gwd]

It is probably the fuel level/pump that is installed in the gas tank. It might of been changed and an inferior product that does not record the levels properly.
There are certain resistance values that can be measured that need to be respected when the float level is at full, mid, and low levels.
For example on a 2002 model year, (yours might be the same):
At "E" on the gage the resistance should be 75 - 80 ohm, fuel level is at 13 - 15% and the remaining fuel will be 0 - 14.76 L / 0 - 3.9 gal.
At "1/4" 123 ohm, level 35%, remaining 34L/9.0gal,
At "1/2" 159 ohm, level 53%, remaining 53L/14.0 gal,
At "3/4" 196 ohm, level 75%, remaining 75.71L/20 gal,
At "F" 230-248 ohm, level 92-100%, remaining fuel 92.74-102.21L/24.5-27 gal,

Low fuel indicator On at 87 ohm, 17%, 17.03L/4.5 gal.
Low fuel indicator Off at 90 ohm, 18.8%, 18.93L/5.0 gal.
Actual results may vary slightly.
Source of info from GM Volume 2 of 2, GMT/02-ML-2 book.

Does this list help?