I recently bought a 2002 Buick LeSabre and was told the float is not working so I have no idea how much gas I actually have. It often dings to say it’s low, but upon filling it I often need less than $20. Is this an expensive fix? Also, when putting fuel in, am I to assume that it is stopping at the correct time?
There is a kit that contains a new sending unit, float and seal. It retails for 239.20 according to gmpartsdirect.com, they will sell it to you for $124.38. There should be an access panel in the trunk under the mat, so dropping the tank should not be necessary. Expect a shop to bill retail for the part plus an hour of labor. You can probably do this yourself if you take the proper precautions and have good instructions. There is a thread on buickforums.com that links to three videos that document the procedure on a Pontiac Bonneville (same platform as the LeSabre, so it should be applicable). The first video contains a dealer price quote of $597 for the sending unit and describes an alternative part number with a price of $40 that can be scavenged to repair a sending unit. Disclaimer: You need to be careful when working on the fuel system. Ventilation are spark prevention are key. Spark resistant (brass) tools would be ideal. A fire extinguisher of the appropriate type is probably prudent, also. There is a post in the thread at the bottom that lists the expected resistance values for various tank levels. It might be worth probing the wiring with a multimeter to confirm the unit is bad before going through the trouble of removing it.
The pump shut off should be reasonably accurate most of the time, but you really ought to keep track of how many miles since the last fill with the trip odometer and make sure it makes sense. They do occasionally shut off early.
When the sending unit goes bad the fuel gauge will usually not move at all. It does sound like it could be an issue with the fuel level sensor in your car. Perhaps the float just needs to be adjusted. Maybe someone bent it out of shape when performing a repair.
For instructions on replacing the fuel level sensor check out the information at arrc.ebscohost.com.