My 96 Impala's gas guage does not acurately measure.  What steps are first before I tear into the gas tank to replace the complete unit. Thanks  

My 89 Sunbird has the same problem,  can anyone out there help us?

The sender in the gas tank is a variable resistor. One resistance value will be full and another will be empty and values in between are in between. So, if you can get at the connector for the gauge (in the instrument panel or between the dash and the tank somewhere - a wiring manual for the car really helps here) you can attach a resistor with a value corresponding to full and the gauge should read full. Likewise if you attach the value for empty, it should read empty. First, you need the wirng manual or service manual to tell what the resistor values are for your car (For example, for my car they are 19 ohms full and 250 ohms empty) and then you buy the resistors at Radio Shack. If the gauge doesn't give anything close to the right reading using the Radio Shack resistors, then the gauge itself is bad. If you get the correct readings with the resistors, then the sender might be bad, but there is the possibility of a broken or damaged wire between the sender and the dash. You can check out the sender with an ohmmeter on the gas gauge sender connector at the tank (without taking the pump/sender out of the tank), but, first of all, you have to get to it and then you have to have the meter on there when the tank is empty and when it's full to make sure it actually changes with level. Of course, if you get to the sender connector at the tank, you can insert the resistors there and can tell if the wiring betreen the sender and the gauge is OK.

So that's why the garages charge big bucks to fixxy for me...   Thanks for the info Ovalgears!

First of all check the ground on the gauges.  As the previous poster stated gas gauges work on resistance.  If you have a bad ground the resistance will be more that it should be and the gauge will read wrong.  You will again need a wiring diagram and preferably one of those factory manuals that show the location of the grounds.  Take the ground wire off and clean it (wire brush and or sand paper) then re-attach it with a star-type lock washer.  It helps if you can get some of the goop eletricians uses to attach aluminum wire to copper connectors to inhibit corrosion in the ground connection.  I would check this first as it is usually fairly easy to get to and will more times than not solve your problem.  Good Luck.