Strange Oil pressure indication

[Bevan]

I have the Vans mechanical oil pressure guage and VDO sender. It seems to indicate correctly until engine shutdown. On shut down, it steadily moves up to indicate max pressure ( >100lb ). Is this an actual pressure indication or some kind of plumbing/wiring error? The transducer is mounted high on the firewall and the pressure line was bled right to the sender.

Bevan

[tim2542]

You sure it's a mechanical gauge? If so it won't have a sending unit, just plumbing to the gauge. I'm guessing it's really an electric one and the needle is just floating around when no power to it.
One thing for sure, you don't have any pressure when the prop stops.
Tim

[Bevan]

I meant to say the gauge is analog (as opposed to digital). It has a needle that swings mechanically but it is electrically operated (using a remote sender). Yes, there is no pressure on shutdown and I would expect the gauge to indicate that.

Bevan

[Raymo]

I agree with what Tim inferred. You probably have an issue relating to related wiring / grounding. A poor ground can manifest itself in strange ways.