Gas gauge quit

[Mondo]

I don't know if it quit all the way but it now says it's a little over half a tank and the tank is full. Dash connections are all plugged in

Any idea where to start?

[Longhorn Man]

We know it isn't the brown wire. I'm sure someone will say it is.
If the brown wire gets unplugged and not grounded, then it goes way past full to the 3 O'clock position.
If it gets grounded out (plugged in or not) it goes to empty.
Sounds like a power problem to me.
I would take a test light and check all the fuses with the ignition in the run position... check both sides of each fuse.
If they all check out good, then i would pull the inst panel, and trace the wires or lines on the panel and see if it is burned somewhere.

[cparman]

you might try disconnecting the wire attached to the fuel sending unit, and with the key on, ground the wire. the gauge should go to full. If it does , i would drain the tank, and pull the sender. IF it has a brass float, remove the float, and shake it. I have seen a bunch of brass floats leak, and fill partially with fuel, and sink. Making the gauge read lower that it really is. IF you have a DVOM ( digital volt ohm meter ) you could sweep the sender, reading OHMS. If I remember it should be close to 0 empty, and close to 90 full

[crm318]

There is a little ceramic resistor piece on the back of the gauge that can go bad and cause this. It happened on my truck. i went to fix-a-gauge.com and bought a replacement resistor and it solved the problem. it was cheap too.

[northerngmc]

Take a look at this link, it is step by step trouble shooting for a gas gauge.

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

[Mondo]

Thanks guys

[ChevyC102007]

Had the same probelm on my '71, everything was plugged in but when I wiggled the wire the guage went back to where it was (3/4 of a tank) found out the wire running from the sending unit forward was grounding out on the door sill plates/ rocker panel (well whats left of them anyways) ran a new wire since part of that one was shredded down to the wire havent had a problem since...........and the wire was a very light tan color.

[65-72 chevytoys]

I had the same problem on mine. It was way past full at the 3 postion. I traced the brown wire and found the disconnect. Now it stays at the E position after adding about 5 gal to an actually empty tank. Now I need to trace and see if it is grouned after I add some more fuel and if it stays on E.

I subscribed to this thread for future ref.
NorthernGMC thanks for the link. I printed that out for future ref. too.

[Mondo]

Well I was embarrassed to say there was a little mishap with my freshly done truck.... My daughter, coming home from school on an old farm road, went off the edge of the road, overcorrected and went about 30 yards into a cornfield (lucky because the other side of the road is an orchard).

Well not too bad cosmetic damage but she went thru an irrigation ditch and launched the truck a bit. Besides new tierods, the jolt put a dent in one front fender and the battery came loose and dented the front of the hood. Paint was surprisingly good, just needs the clear buffed out on the front edges.

Long story short, I think something came loose or shorted but it all seems fine on the dash. I'll have to trace it down, just seems funny that it's half full and not empty or full.

[sswitzke]

might have a small hole in the float inside the gas tank.

[special-K]

Mine started reading a bit less than 1/2 and not moving.So,I figured the float was stuck.I ran out of fuel one day.When I filled it up,the guage went to full and worked fine for awhile.Now it`s back to stuck.
I have two aux.tanks and one guage reads about 1/8 and the other way full.So,I have all kinds of crap to run down.

[Mondo]

Well it gets worse.
Today the truck quit running, like out of gas. The gauge now say empty. So I think maybe it is out of gas. Put some gas in (it's in the bed) and it tops off. Still won't start....

Seems I have more to check than wires

[Mondo]

thought I'd end this post with the answer(s)

First off, with my fuel tank mounted in the far back of the truck, I noticed the fuel hose going from the bed to the tank was kind of kinked. So a couple weeks ago I had my friend at the muffle shop bend some pipe to cure it. Well, it seems we made it a little too low and the fuel would back up rather than go to the tank. So it was out of gas though it looked topped off.
Shortened the fuel hose from the bed and solved that.

I don't know what caused it but the sender unit shorted out... new sender, all good (though it say 7/8 full when topped off).

Now, to save up for new fender/hood/repaint

[garold99]

Mine just reads empty all the time.

[cparman]

the float in the gas tank could be full of gas making it read low? If you disconnect the sending unit wire from the gas tank, and connect a test light to it, and look carefully, you should see the test light lite up and blink. it will not be a bright light, so look carefully