fuel sender worn out and died

[apollo13]

I replaced a fuel pump. By the way, the "micro-encapsulated bolts" for the fuel tank are no longer available, They just gave me plain cadmium-plated instead.
I rubbed some beeswax on the thread - and it has not leaked.
I put 17 litres in and started it. Fuel guage only showed 1/8 which is too low. I only drove a few km then left vehicle in garage.
Then next time, fuel guage did not move, and I get low fuel light on.
So I thought the float had fallen off the clips. I pulled the thing out again, but float was still attached. examined it under bright light, and see that the wire goes
to the spring around the hinge, which then connects to the wiper. The wiper is still making contact. I checked the plug and there was no dirt in it.
I plugged it in, and turned key to on, and the needle moved. So I put pump and sender back in the tank, tightened the bolts, attached hoses and tried again.
Fuel guage stuck on empty. I checked the guage by connecting a 100 ohm resistor, and it swings to just below half.
So I presume the thing is old and worn, and juggling it back inside the hole disturbed something.
I see on GMH parts catalogue that the sender is not available seperately. You have to get the main assembly with the fuel plumbing. I doubt they would be in stock anyway.
I saw an on-line wrecker selling the whole lot, but it could be from a hoon's car with hard suspension, so that it had a whole lotta shakin going on.
Are these senders repairable?

 

[markovr]

If you are handy with a meter reading resistance it should read 283 to show empty ...97 to show halfway and 40 ohms to show full. ..unplug the wiring connector at the tank and put the meter across the outside terminals at the sender unit of the tank to see if it reads this to prove its the sender thats stuffed ( done quite a few and never seen them go bad) or to see if its wiring or gauge unit:
You could get a resistor and unplug the sender at the tank and put some where near these values and across the two outside terminals of the plug and see if the gauge moves to prove its stuffed or it has a open circuit somewhere
If you need a sender they are easy to obtain cheaply at the wreckers