Gas gauge question

[CG]

When I bought my truck all my gauges worked fine, it even had a working tach. I used to drive it around much more than I do now so I would have noticed a weird problem.

Quite a long while back I bought a restored gauge set up from a board member. I was going to use it for a now long gone project. New bezel, restored gauges, even had a vac gauge put in. Well it sat in the closet for a few years before I did anything with it, and one day I decided I might as well spruce up the K20 some and put this gauge assembly in there.

I took out the old gauge unit and sold it since I had no use for it. I put in the new (even though I had it for several years) panel in my truck. Right off, the temp gauge pegged. I figured probably a ground problem or something along those lines. No biggie. I still havent hooked up the vac or oil pressure gauges. My truck has a stand alone 80lb oil gauge on the underside of the dash anyway that works great. Speedo doesnt work right either. I took it on and off several times ... sometimes it works, sometimes it doesnt. Also the tach doesnt work correctly. Sometimes it reads what I think should be about right, and sometimes it runs almost pegged.

Non of this really bugs me, its my own fault for not trying it out right away. I figure I can fix whatever is ailing it when I feel like yanking the whole thing out. (someday)

One thing I discovered is the gas gauge is out of a large truck. It has those weird idiot lights that flash on once in awhile. They are words, Ive forgotten what they say.

Ok after this long blah blah blah. Ive havent filled my truck up all the way for a very long time. Today I figured with gas prices going up I should keep it topped off as much as possible. Read almost a qtr tank when I started. At 15 bucks it clicked off full. I looked in there, yep full, gave the truck a little shake (no idea if that does anything, but Ive seen others do it lol) yep still very full.

So I hop in the truck, fire it up, and the gauge reads a little less than half a tank, but I know that baby is full to the brim. Now I know my gauge worked perfectly with the original set up so do you think that...

A Since my gauge panel has other weird problems this might be electrical?

B Since this gauge is out of a large truck it just doesnt read correctly?

C The sending unit in my tank is messed up and its just a fluke it happened now?

[sameyrasmea72]

Since the gauges have been "restored" I wonder if he took off the needle to paint it? If so It might be in the wrong location. You might need to calibrate it.

I doubt your sending unit is bad because it worked fine before you messed with the guages.

[CG]

Originally Posted by sameyrasmea72

Since the gauges have been "restored" I wonder if he took off the needle to paint it? If so It might be in the wrong location. You might need to calibrate it.

I doubt your sending unit is bad because it worked fine before you messed with the guages.

Now I never even considered that, cause the needles have all been painted.

BTW, Im not bagging on this guy. And honestly I dont even remember who it was. I remember I picked him because he was one of a couple of guys doing a lot of them back then. I know if I had installed it right away and it turned out to be a problem with the gauge he would have made it right. Not his fault it sat for years.

[sameyrasmea72]

The gas guage needle is one of the few needles that comes off/on easy, so it might be a possibility.

[CG]

Busy day on the board ... Bump for the evening crowd just in case there are any other ideas floating around out there.

[VetteVet]

Have a look.
http://www.6066gmcguy.org/Electrical-02.htm

[CG]

Hey thanks thats a very cool link!