Digital Dash gas gauge not reading correctly

Today I ran out of gas in my 87 Guick Grand National. I have the digital Dash and the gauge read 5 gallons when I ran out. When I gassed the car up it took all of 18 gallons to fill it which is the capacity of the gas tank(18 gal tank).

How do I go about fixing this gas gauge to get it to read correctly??

Here is a picture of the gauge when it is full(F).
http://performance-auto-group.com/images/eBay/Stock-0031/Large/Stock-0031-e040.jpg

I know that alot of the gas gauges are off. Probabally has something to do with the float in the gastank

Contact Kirban's or Cotton's. I think you need to have it recalibrated.

Kirbans or Cottons??????Who are they and how do I contact them?

They are vendors that specialize in turbobuick parts

www.cottonsperformance.com is jack cottons website.

I cant rembember Kirban's website off the top of my head

Thanks guys.

I will look into Kirban and Cottons. I just found Kirban at www.kirbanperformance.com

try diconnecting the battery cable'S,, both of them

then touch the + cable to the - cable,and hold for a few minute's,,,this will drain the capasitors in the computer and it might reset for you,,this worked worked on my speedometer,, ,it now read the right speed

Interesting idea. Never really thought the small caps used on pcb's hold power that long. I'll add that to my book of tricks.

I had the dash face off because of lights out,,and lubing the shifter,,
DON'T EVER LET A DAMMED IDIOT ALONE
THEY HAVE HABITS ,,LIKE PULLING GAUGE NEEDLES TO SEE HOW THEY ARE MOUNTED...all I had to do is fill with gas ,position the needle correctly,,
I know this guy doesn't want to cross my path for awhile