Is there any reason for sudden loss of oil press?Before I shut the car off I had 45psi on the gauge at 2000rpm.I shut the car off,then restarted 10 min. later and nothing on the gauge.I disconnected the gauge at the block after checking the oil and fired it up,no oil coming out of the sender port.It's a 69 383 that's never been apart that I know of,any ideas?