how about taking some thin metal parts tag wire & wiring the float/arm up to the upper stop & installing it this way. If it still reads "full" when you get it in there & hooked up then the only thing left is the liquid level in the tank isn't high enough for that particular sender or the tank isn't getting filled as much as you think & you could dunk the sending unit in a bucket of water outside the car with the ground & hot leads hooked up & see how it acts which would let you reach down & move the float thru its range of travel.

The thing is that the sender needs to be in the lowest position to be able to get it back into the tank......

I had thought about putting it in bucket of fuel to see if it reads any different.......

What stinks is that this sending unit is stainless......so it's a PIA to bend........I know that because I tried to bend it a little to make it lay on the very bottom of the tank........

Ive had two floats crack and fill with fuel the stainless sender units are very tight where they hold the float.Id say your float is hitting the top of the tank before the guage reads full.Both of my senders read 3/4 when tank is full their driven me mad.I mucked around with my spare sender unit the other day and found they need to be adjusted at the full stop tang to get a full reading you have to bend it were it comes out of the sender unit.I now get a full reading out of the tank while i only ever got 3/4 full.And then you have to then adjust the empty float hight.
Now im worried i might have the same problems as you as the float probably will hit the top of the tank through its travel.I will have to measure the travel the float will need from empty to full.
If its more than the hight of the tank im done with fuel guages i will just have to remember ive got 1/4 tank when showing empty.Good luck with yours.

I just filled it up with fuel and went for a test drive.......The gauge goes to halfway and that's it.........this is even after I've bent the float arm down so it'll make the gauge read higher......

I'd submerge it in a large bucket of water & check it & my only remaining idea is, that the tank isn't getting all the way full. It's grounded, the float isn't waterlogged, the rheostat functions... Do you believe in Karma, curses, voodoo, or good old fashioned Murphys law any of that sort of thing.

Anyone have a picture of how that ground from the sending unit should look like? Where on the unit and chassis are the best places to put this ground wire? I need to do this for my new unit as well. Thanks !!

Here's the stock ground strap. It goes from the metal line coming out of the sender to the metal fuel line. It bridges the rubber hose. You can do the same thing with a piece of wire and two fuel line clamps.

Thanks much for that. I didn't know there was an actual grounding strap (mine doesn't have one).

Does anyone have a picture of this (or the wire) installed on their car?

As far as metal lines from the sending unit, I have two - the 3/8 for the fuel and the 5/16 for the return. Does it matter which one is grounded?

Thank you.

Thanks guys.

So, if I was to go with the 12 ga. wire approach as was suggested earlier, I can just use a small hose clamp to secure this to an exposed portion of either of the two metal lines from the sending unit and secure the other side to the chassis, correct?

Thanks!

I am not sure, but I believe it could be the ground strap that goes around the rubber lines at your tank, it has to be clean to ground properly, also they make a larger ground strap for a hemi fuel line, I have one in my garage, but I am not sure what size it is, but it is bigger than the original, thanks