Problem sorted! tested fuel sender unit (in the tank)-worked ok. replaced voltage stabiliser-still same problem. Used a multimeter to test wire integrity, no continuity from gauge to sender. The loom has a multi block connector under dash on offside. I split this, the rear part of the loom was ok, the wire from gauge to the connector was not continuous and was earthing out somehow, with ignition on and the multi block split gauge still read full. Ran a new wire from gauge to multi block problem sorted!
Now what was it shorting too? Will save up for a new loom it's 33 years old!
