All,
I have another thread that was running at the beginning of this about my fuel tank on my 2016 F250 Super Duty Excursion conversion. After a few years of thinking i only had a 30 gallon tank it turns out I have an actual Excursion 44 gallon tank but they used the sending unit form the 30 Gallon F250, so my Excursion basically would read empty when i still had 14 gallons of Fuel left

With some fantastic help from the guys on this forum we were able to determine if we installed a sending unit form an 05 Excursion would work as it was the only year where they did not have the pump as part of the sending unit. The it used an external Fule pump as does the 2016 F250.

Well we installed the new sending unit in the tank, we still had around a half tank left when we installed it. Hooked it up read about a half tank as we thought.
Fast forward: As I drove this last week my Tank gauge showed i was actually having an increase in Fuel! Now that would be fantastic if it were true LOL!, however as you can tell the gauge was obviously reading in reverse, so brought it back to the shop that is doing this for me and we thought it would just be a wire swap, sounds simple? We all thought so but all it did was to jump all the way to full! Which it was not! Aslo my DTE was incorrect but that was expected as the unit still thinks it has a 30 gallon tank, and I know that is a programming issue.

So what I am looking for here is some help and advice to figure this out and if any one has any ideas, suggestions' etc. it will be greatly appreciated!!

Below is the thread where all of this started, again, really need some help!

Custom Fuel tank needed - Ford Truck Enthusiasts Forums (ford-trucks.com)

 

Here is the big question, is this just the gas "gauge" issue now, does the truck now actually allow you to use the full 44 gallons before it stalls out?

 

I have not yet filled the tank up but the tank read almost empty when we took it out so when it was connected to the new sending unit it read about a half a tank but then kept climbing the more i drove it.
I am pretty sure the sending unit will now cover the whole tank as the pick up compresses to the bottom of the tank and it went from reading almost empty to about half a tank when hooked up. Again the surprise being the gauge going up rather than down. Then when they chenged the wires around it went right to full and we had thought i would do the opposite, so this is where we are stumped

 

Im not a tuner, but you might just need a negative flipped to a positive or such in the tune.... its all maths in there.

And if it reads backwards, but otherwise works, and cannot be fixed more than scaling properly in the tune, so be it, just remember which end means full. If it really bothers you a ton, take the cluster apart and put E and F stickers over the fuel gauge so it is lettered properly, lol

 

I am a stickler for wanting everything to work properly and if something in the software will fix this I am all for it! But I am not sure if you can "flip" the negative and the positive in the Software, but i do think it could be properly scaled in the software once this problem is tackled!
Stickers on order just in case LOL!!

 

The other alternative is, if you have Torque setup in the dash, you can add a custom gauge to the dash, record what the reading is at full, and at empty, and adjust its math to compensate, example if 20 is empty, and 140 is full, you could do -20 to get the base to zero, and then use some division and multiplication to turn the 0-120 range into a percent and apply it to a gauge, torque make that kind of stuff a snap if you know how to do some math. On my cobra i added a gauge to show the Turbine speed of the supercharger, i know what the ratio of the pulleys was, so i had it feed from the RPM input and math it out so the gauge would show the speed of the screws in the blower, more less for cool and novelty reasons in that example.

Throttle position on ford usually also starts at a base number and not zero, i think on my mustang, throttle body fully closed is a value of like 20, i forget what WOT is reading wise, but so it didnt constantly show 20 i subracted 20, and then converted it to a percentage so i could show it as 0-100% instead of the raw reading.

 

Thanks Master X, I have found it has nothing to do with the wiring but with the Ohm output of the unit. I just need to find a knowledgeable place that can program the gauge to match the output
My issue now is that the old unit that wass pulled out was tossed and i wanted to measure the ohm output of the original 2016 unit.to get a baseline