Help - Strange Oil Pressure Gauge Behavior Options

[Tom1394racing]

I am working towards first start on the 3.2 Short Stroke installed in my -6 GT project.

While cranking the engine over with the fuel pumps and MSD disconnected and the spark plugs out, I am getting no oil pressure reading on the dashboard gauge. To verify if I do really have oil pressure, I connected a mechanical gauge in place of the sending unit and cracked open the cam oil line. I got 30 psi on the gauge and plenty of oil leaking from the cam line.



The gauge registered around 30 psi, I just did not capture it in a photo.



So, it seems like the engine is making good pressure while cranking. The problem must be in the sender or in the gauge. To check these, I connected the sender to a variable air pressure source and checked the gauge.



The gauge showed the following readings

Key off, no pressure applied to the sender:



Key on, no pressure applied to the sender:



Key on, 50 psi applied to the sender:



Note the engine was not cranking for this test. All looked good for both the sender and the gauge.

Stay tuned.

[Tom1394racing]

Next, I reinstalled the sender in the crankcase, connected the sender wire and repeated the test to see how the gauge behaved.

Key off:



Key on:



So far, just like when I tested the sender with external pressure.

Next cranking the engine:



When cranking the engine, the dial on the gauge moves back to the key off position???

I know I am making oil pressure in the engine and I know that the sender and gauge respond correctly to applied pressure. However, when I apply the starter to crank the engine, the gauge moves back to its key off position.

I am stumped at the moment. Any Ideas?