I'm about to replace the oil pressure sending unit on my 85 XJ6. The current one seems to be misbehaving, ie. on a cold startup, it sometimes reads low (20'ish PSI) and I would think at cold it should read at the high end. When hot it settles down in the mid range of the gauge but sometimes drops down and then back up. It may very well be a bad electrical connection, but since I have a new replacement, I plan to clean the connections and replace the sender as I'm already in the area.

My question is, should the new unit be "primed" with oil before installation? I plan to fill it with a syringe. To answer my own question I suppose 40 PSI of air and 40 PSI of oil is the same thing?

 

Nope, no need to prime it

Cheers
DD