EFI engine swap, gas gauge issue

[RPIcka]

I just bought a 1972 K20 with a swapped in '98 5.7l vortec. the gas tank was pulled out of the cab and a tank from an S-10 was added on the frame rail. the gas gauge doesn't work. anyone have any experience with this or suggestions? Thanks.

[69heavychevy]

i would start with the sending unit, make sure it works and is the correct resistance (90ohms)

[VetteVet]

Pull the sending unit wire off and with the key on, the gauge should read way past full.
Ground the sending unit wire to a good ground, and with the key on the gauge should read empty. If you get these readings, then the sending unit is not grounded to the frame or it is defective. do not put any hot voltage on the sending unit wire as it may cause an explosion or fire.

I forgot to ask if you are running an in tank pump and gauge or a separate fuel pump with a stock sender in the tank?

[RPIcka]

It is an in tank pump so the gauge wiring is different than stock, thats my problem

[Ackattack]

For my 68 I used an LS1 F-body fuel tank. It has a odd value for full and empty. I'm using a programable fuel gauge from autometer. There is a calibration procedure where you set it empty, fill it up, and set it full. (I added about a gallon before I set it at the "empty" mark.)

[RPIcka]

I want to use the original gauge with the newer unit in the tank.

[MARKDTN]

Stock you should have about 90 ohms resistance with a full tank and 0 ohms resistance empty. Take and measure what you have with the new tank empty and full. You may have to have the gauge rebuilt with the new values. I did not know that GM had changed anything, but I may be wrong.