Oil Pressure Gage and Sending Unit Revisited

Mattax said

Gauge test was with the engine running.
So yes the IVR was also supplying the fuel and temperature gages.

Block has a ground strap to the firewall.

More resistance should result in the pressure gage reading lower. Got the opposite problem here.

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I would agree with the more resistance not causing your problem except in the case of a ground loop. If something else is pulling a lot of current, the ground difference can turn into a voltage source for the sender loop. Not highly likely, but all the unlikely stuff happens to me.....