Sub tank fuel gauge

[bobbealerov]

G'day all,
My sub tank fuel gauge returns to zero when the engine is switched off but as soon as the engine is switched on it goes right up to full and stays there. I have changed both the pump and the sender unit, and checked the resistance readings through complete travel. I have checked the fuel transfer and that works fine. I have disconnected the battery several times and fitted an extra earth strap from the tank to the chassis. I have even emptied the tank several times but nothing seems to work. Does anyone have any ideas on what else to try.

Cheers