Z725 fuel gauge issue

[seajay55]

I have a new 725 and the fuel gauge either reads beyond full or below empty. If I cut the key to the "on" position it reads beyond full, however, when it the engine is running it shows below the empty mark. Does the engine need to be running to activate the gauge or should it show the correct level when turning the key to the on position? Trying to determine if something else is going on other than a bad gauge.

Thanks...

 

[GreensvilleJay]

Normally, you only need the key to be on not the engine, +12 from the battery, through the switch to the meter and then sensor to ground.
An 'over full' reading usually indicates a shorter sensor or the wire to it though why yours empty when running is mystery UNLESS vibration is grounding/opening the wire .
One of those gotta be there to SEE what's going on and I bet getting TO the fuel sensor wire will be a real 'pain'.

 

[Wull]

As above it will be a wiring issue, shorted etc.