I have been away for a while I started my Vantage today and noticed that all is normal when turning on key, but as I push the start button the fuel gauge drops as the starter swings, it recovers as the engine fires up.
The engine starts right away and no evidence of a low batt, is this normal? The dropping of the gauge ....?
I can't recall seeing this but may just never have noticed.

 

pretty sure mine does the same thing on startup

 

I checked with my V8V, no needle moving while starting.
Hope this helps

Christian