Can Anyone Help?

I have been trying to figure out a sending unit slash fuel gauge problem for weeks.....I am very well familiar with how everything is suppose to work....I have three wiring diagrams but I still cant figure out what is wrong.....basically heres what happens in a nut shell....my gauge is good...my instrument cluster voltage regulator is a new solid state .....everything works fine until I put fuel in the tank....everything reads fine....checked and double checked and quad droople checked.....has anyone ever had a problem where the gauge and sender works proper until fuel hits it?...I have tried three senders and two gauges...still the same problem...Please tell me that someone has had this problem

other_shoe said:

What precisely is the problem when you put fuel in the tank? I'm assuming it shows no fuel or not enough fuel.

If it is showing empty when you put fuel in, it could be the ground for the tank.

It could also be that the angle of the float arm is off so that it is not registering enough change in angle for the rise in fuel level.

If you are reusing the same float, it could also be that you have a hole in the float, but I'd suspect you'd notice that when removing the unit.

The angle is wrong on mine right now, but I need to run the tank down a bit so that I don't have as much fuel to drain. There are a couple of posts on here about how to bend and test it.

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The exact problem is that when I remove the tank with the sending unit still connected and I tilt the tank upside down and put a hot lead on the sender that has 5 volts and ground it against the chrome molding on my 65 the gauge works fine...its only when I add fuel to it that gauge doesn't work....I know and have good ground...I have bent the float arm and checked the ohms reading....brass float by the way......I have checked everything that would be the obvious things that people suggest and I am no stranger to electrical but its not anything obvious......I ordered a new spectra sender.....I have good ground..I have a new solid state instrument cluster voltage regulator....good fuel gauge.......it just shows empty no matter how much fuel I put in it.....well not empty but the farthest it has read was on maybe a quarter tank and the gauge moves rediculosly slow...I ask for help because I hope that someone will tell me something I don't know and maybe just maybe someone has encountered this problem.....THOUGHTS?