Gas gauge faulty on 00 gmc sierra

Question

i have just bought this truck and will assume its something bad. i noticed like every five times u start your engine or cycle the key the gauge will display correctly but mostly it will stay on the very bottom of where it goes when the truck is off. basiclly it wouldnt move from its off position.

what is the first thing i should do myself before having it looked at?

Answer 1

I don't have an answer for you but my 2000 sierra sle has done the same thing for years.  After I have burned a few gallons of fuel off, the gauge is correct and is no longer a problem.  I would also like to know how much it is to fix it and what to do.

Answer 2

This is a common problem for GM's.  I've seen the gauges defective, but the majority of the time it's the sending unit in the tank.  You can turn the key on and then unplug the connector at the fuel tank and see if the gauge changes.  They usually go all the way to full when you unplug them.  It should go one way when you unplug it and the other way when you ground the sending unit wire. Hard to say which wire to ground depending if it's single or duel tank, or which size engine.  If the gauge changes, then it's a bad sending unit, which is the more common of the two to fail.