Refilling and fuel cap

[Ashmyster79]

As some are aware I recently bought my 2002 3.2s I got it cheap so knew there would be issues. Fuel gauge is saying empty when it is not. Have filled up but still the orange light is on and pin on empty

Car garage said fuel sender unit needs replacing. I have checked the fuses all fine. However when I fill up or try too the petrol pump keeps clicking like it would if the tank is full which I know it isn't. This is tricky to judge as continuing and bypassing the clicks I could over fill although I doubt I will.

So my question is. When this happens why is that?
Also the fuel cap is pretty bad on the outside. The thread is good but think needs changing. I remember from my 350z when I took fuel cap off I would get a release of pressure which I don't get on the boxster. Is this something that should happen?

I am going to check the fuel sender connections and see if the float is stuck. Will do this before I spent £300 at the specialist to get it fixed.

Thanks for the information in advance.