I've done a good bit of searching to see if I can find a similar issue but haven't seen it so far.

I've been building a custom digital display and nailing down the fuel level has been the most difficult part. We went back and forth for two weeks changing resistance levels in the software files, thinking we finally got it right, only to discover we didn't. And the more I've been looking into it, the more I'm thinking it's something with the sender. I just replaced it in Sept 2022 with one from AI One. I've had issues for years, even with the stock gauge and the Speedhut gauge, but this is on another level. OneGauge said they applied filters so it shouldn't bounce around, but that's not the biggest issue. I can't even get it to read the same between keying on at different times, and that's without changing anything else or changing the fuel level. I've checked with a mulitimeter and those readings are different all the time too.

I'm using a CJM first gen fuel pump hanger, the AI One sender, the FEED fuel collector box (not that it matters other than moving the sender and using extra wiring to make install and removal easier). I thought maybe the extra wiring was interfering with the float, and it might have been a bit because it started reading more accurately last night when I moved the wires out of the way during install, but this morning it read different again.

There is 1.7 ohms of resistance between the tank and the dash. I have the pump and sender grounded on one of the posts that used to hold the Bose snake, and then I have a wire going from there straight to battery ground. I checked resistance on that and it was 4.1 ohms initially, then I changed the order of how I had them grounded and got it down to 2 ohms. But I'm wondering if maybe the problem is grounding it somewhere other than the ground going to the dash. In the FSM, it looks like it goes to the dash and eventually grounds on the engine block, at the top of the UIM.

I've also gotten different readings from the same location (in the white connector just outside the tank opening) depending on whether the battery was connected, key off, or key on.

I've thought about running new, larger wires, and with no connectors all the way from the hanger to the dash and from the hanger to the battery ground. I'm also wondering if I should run it to the ECU first (Elite 2500) and send it through CAN to the dash rather than going straight to the dash. Or maybe rather than having the wires go through the connector on the hanger, install some bulkhead posts. I have seen some burn marks on the terminals inside the tank, but it doesn't seem like it was enough to melt the plastic like on the stock hangers.

I connected my Speedhut gauge and it was reading about the same as the digital display, which is one reason I'm thinking it's the sender or something related.

Any thoughts?