No oil pressure on new motor??

[Crashly]

I just put the new motor in this afternoon and there is no pressure on the gage. The oil pressure light does go out when the motor is started. I checked for flow by cracking the passenger side chain tensioner and I am getting an oil flow. I pulled the sending unit and the hole was not clogged. I then cleaned it out with some carb cleaner and reinstalled it and still no oil pressure at the gage while it is running. When I turn the key on the gage needle comes from the bottom and stops on "0". When I unplug it from the sending unit the gage goes all the way up. When I lightly rev the motor the needle does not move. I also cleaned the pin connector and everything that I could as far as electrical connections still no luck. The sending unit worked well before the motor rebuild and the re-builder reinstalled the unit along with the chain tensioner. So what do I check now? From what I can discern I need to check the gage and wiring with a "potionmeter", I have never used one of these. Then I need to check the oil pressure via a mechanical gage. Anybody have any tips or advice?

[regency]

When I received my engine from the so called "builder", I too had little or no OP. After months of his BS, I removed the engine, dis-assembled it to find that there was a missing oil pump seal.

If you don't have OP with the mechanical gauge installed, then you probably used my "builder" too!

[dtw]

Aside from the bad gauge, that was the first thing I thought too - missing oil pump seal. Get a mechanical gauge on it before running the engine any further.

[Nitrometano]

mechanical pressure gauge is the way. Would be very bad news to open the engine because a seal is missing.