How can I check the oil sending unit, or check that the oil pump is working? I just did a motor swap and the oil pressure is showing 0. There is oil moving through the external filter (I removed the line to see and its moving) does this mean the pump is working?

I am scared to run it with the gauge not working, I want to ensure the oil is pumping so I don't blow the motor. Thanks

 

The best way is to remove the oil pressure sending unit from the back of the block and attach a manual pressure gauge to the port. Flow does not always mean pressure.