I got a 2000 Chevy 3500 gas 350 with two tanks. The back tank is rusted out and not worth fixing, so I ran new fuel lines and installed a new pump and sending unit. But I can't get the fuel gauge to work now. What do I need to do.
Thanks Aaron

 

Dont know a lot about these, but I imagine you also bypassed the switch for switching between the 2 tanks....I am guessing that the gauge wires run through that too.

 

Sending units are really just a float attached to a potentiometer, a device that reads a different resistance based on it's position. I'm not sure how these dual tank designs work, though. Are the tanks independant from one another? Would each have a pump and sending unit? Does the dash have two fuel gauges, one for each tank, or just a single one?

I've worked on fuel pumps before, so I might be able to help you out.

 

I am thinking there is a pump and sender in each tank.......one gauge, gets shared with a switched wire to it.......just a guess

 

That was my assumption. By "the gas gauge isn't working" I'm going to guess he means it's registering zero at all times. If that were the case, it's likely just a wiring problem. Probably needs to check for continuity from the tanks to as far as he can.

I'll try to find some time to do research into this. I don't think there'd be any technical issues with removing the one tank completely, though there is a remote possibility that the computer may demand at least an empty signal from the tank you may have moved. Unlikely, though.

 

In your truck, as in mine, there is a fuel modulator that reads the fuel level in BOTH tanks and then outputs the combined total to the fuel gauge. When this modulator detects low fuel in the FRONT tank it triggers the transfer pump which sends fuel from the rear tank to the front tank where the vehicle fuel pump is located along with the sensor.
Both tanks need to send a valid signal to the modulator or the fuel gauge will not work,
I m currently trying to bypass my modulator so that i can run off the front tank alone as my rear tank rotted out and I cannot find a replacement.

The modulator in the cab chassis truck that i have is attached to the frame rail under the driverside door.

 

Don't suppose you ever figured out how to make your gauge work off just the front tank? Been working on this all day, blue with white tracer connected to purple wire and balance module completed disconnected, still can't make the gauge work.