Originally Posted by demian5 (Post 8001506)

Pull the wire off the sender, turn the ignition on and ground the wire to the body. It should go to full.

- If it doesn't move, try it at the gauge terminal (connect to ground). If it moves at the gauge, then you know the wire has an open (you say empty, but if the gauge was showing full then I would tell you it may have a short to the vehicles body).
- If the gauge goes full AND the wire is good, the sender is easy enough to pull and take a look at. Make sure it is grounded to the tank and the tank is grounded to the body. A simple DVOM resistance check between components can show that.
- If the gauge doesn't do squat, check the power to it .
* If it has power, check that the resistor on the gauge isn't blown. I've seen many a gauge replaced for a $2 resistor that can be replaced! They are sold through truck and car shop.
* If it doesn't have power, well, figure out why or jumper power to the gauge directly (at least jumper to figure out if the gas gauge or sender is working).

Originally Posted by ApacheIvan (Post 8001521)

Perfect explanation! You can do this with oil or temp gauge as well.

Originally Posted by RenoKeene (Post 8001551)

Could be as simple as the float. I'm on my third aftermarket one now. They are so poorly made that ethanol eats holes in them. One of them actually split but not at the seam!

Originally Posted by 71CHEVYSHORTBED402 (Post 8001677)

Reads a pinch over 1/4 when full. At 1/8 it's time to fill up again. :alky:

Originally Posted by demian5 (Post 8001584)

Fuel and temp gauge for sure, but the oil gauges are mechanical in these trucks from the factory from what I have seen.

Originally Posted by 71CHEVYSHORTBED402 (Post 8001677)

Word is these are good float replacements: Jeep OMX-1772901 (a.k.a. 17729.01).

The gauge in my driver doesn't work right. Actually, I witnessed it register for a second, when it was cold as heck. It works well enough for me. Reads a pinch over 1/4 when full. At 1/8 it's time to fill up again. :alky:

Originally Posted by demian5 (Post 8001686)

Sounds like your resistor is bad. My sons 86 operated like that, turned out the resistor on the rear of the gauge was bad.

Originally Posted by 71CHEVYSHORTBED402 (Post 8001730)

Far as I know there's not a resistor on the 72. It has a gauge cluster, for whatever it matters.

Originally Posted by demian5 (Post 8001794)

http://67-72chevytrucks.com/vboard/s...d.php?t=477811

http://www.truckandcarshop.com/6072.html Page 45

Originally Posted by RenoKeene (Post 8001551)

Could be as simple as the float. I'm on my third aftermarket one now. They are so poorly made that ethanol eats holes in them. One of them actually split but not at the seam!

Originally Posted by Canuckvetter (Post 8001864)

Mine did the same always on empty. Float had a pin hole in it. Changed that 2 yrs. ago. No issues.

Originally Posted by 71CHEVYSHORTBED402 (Post 8001677)

Word is these are good float replacements: Jeep OMX-1772901 (a.k.a. 17729.01).

The gauge in my driver doesn't work right. Actually, I witnessed it register for a second, when it was cold as heck. It works well enough for me. Reads a pinch over 1/4 when full. At 1/8 it's time to fill up again. :alky:

Originally Posted by demian5 (Post 8001506)

Pull the wire off the sender, turn the ignition on and ground the wire to the body. It should go to empty.

- If it doesn't move, try it at the gauge terminal (connect to ground). If it moves at the gauge, then you know the wire has an open (you say empty, but if the gauge was showing full then I would tell you it may have a short to the vehicles body).
- If the gauge goes full AND the wire is good, the sender is easy enough to pull and take a look at. Make sure it is grounded to the tank and the tank is grounded to the body. A simple DVOM resistance check between components can show that.
- If the gauge doesn't do squat, check the power to it .
* If it has power, check that the resistor on the gauge isn't blown. I've seen many a gauge replaced for a $2 resistor that can be replaced! They are sold through truck and car shop.
* If it doesn't have power, well, figure out why or jumper power to the gauge directly (at least jumper to figure out if the gas gauge or sender is working).

Originally Posted by demian5 (Post 8016263)

The original poster never came back to say he fixed anything.

You should start here and report back.

Originally Posted by Freestate (Post 8016269)

I think I'll start with looking at the float. I have a gut feeling its that, then I will work through this process if that's not the fix. Thanks for the help!