It's an electrical gauge running off the level sensor. If it's a new installation - bring it back and make 'em fix it! It's bound to be an electrical issue though, and if you have the time to spare, it'll be a good learning experience. You can follow all of the wiring and check that all the connections are sound and that there is power at all the terminals - start at the relay that supplies power to the sender, and then check for continuity at each junction along the way. Otherwise, the easiest thing would be to call an auto electrician...

 

Just need to put some more fuel in buddy

 

Dunno exactly but to me if it was just an electrical or sender issue wouldn't the gauge sit at empty when the car is off?? Not way below empty like in the pic? So maybe a faulty or damaged gauge. If it does sit on empty when the car is off and then when you turn it on it goes below empty, maybe the wiring is reversed somewhere and making the gauge work backwards?


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Both of my Patrols had the same problem, change the sender, they have a habbit of dying. once fixed, run your car on petrol for an hour a week to clear out any dirt from the filters, pump and if the sender unit is left to air out, dirt will stick to the moving parts and thus stopping it from moving freely so always keep a full tank and excercise that float..

You could try returning it to them, but I doubt theyd help, knowing how common these senders **** themselves.. Do it yourself.

Put blocks at the front of the tank..
Use a jack with a block (youll need to lower this end)..
Unscrew the 4 nuts..
Lower the jack slowly until the hoses are easily accessable..
Unscrew the ring clamps and slide the hoses out (I think it was 4-5 hoses)..
Then drop the tank..

Before you do it all, check to see if they cut a hole in your floor, to make servicing easy..