2001 Ford F250 7.3 diesel
Oil pressure gauge drops to zero once the truck warms up
When accelerator is pressed pressure gauge comes up
When truck idles, pressure goes back to zero
low pressure Oil pump, Oil sending unit, oil cooler kit, oil and filter have all been changed, even gauge panel has been changed

The truck runs fine - does not seem that anything is wrong, except that gauge reading is down to zero

Any suggestions?

 

First thing I would do, if you haven't already, is get a real gauge on it, not the one on the dash, then go from there.

 

Agreed, Oil Pressure Test should be done.

 

From what I can recall, the factory sending unit only needs to see 5 psi to register pressure. Hopefully, its an issue with the gauge or sender. Usually these symptoms point to a cracked block...

 

Echo... Echo...
Get another gauge on there. Preferably a physical one.

 

sounds like a bad pressure switch.