Fuel Gauge not working after Fuel Pump replacement

Hello, it sounds like possibly the wiring harness may have gotten pinched if you had to lower the tank on this one to replace the fuel pump. Or you did get a bad sending unit. There have been a lot of bad parts lately. But I would check the wiring back near the tank, I don't think it's going to be anything up front if it were working before the change out.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Yes, here is the wiring diagram for the fuel pump and the gauge. So, the fuel level sender has the purple wire labelled as Chev and goes to the ECM. Then to the level sender and then to the instrument cluster. There must be a connector involved somewhere there due to the wire color change. The other wire there, the black/white changes over to just a black wire that grounds a bunch of other sensors and actuators and then goes to the ECM. The second diagram is where the purple wire ends, and the third is where that black/white wire ends. But if that wire were being used you would have trouble with a lot more components. So, it looks like it's just the purple wire labeled Chev.

I'll try to locate the pinout for the instrument cluster too if you want that.
Okay, that purple wire goes to the ECM, the ECM then outputs the signal on a different wire (fourth diagram) an orange wire and then to the instrument cluster. Fifth diagram. Pin C14 at the cluster. And I know how tough trying to work on the ground is, I do it all the time doing mobile diagnostics, so I understand.

No problem, let us know if you need any other information in the future. Hope it goes well for you.