Dumping oil into the pressure sending unit hole isn't going to do any good if it can't flow backwards thru the oil filter.
1) What you need to do is slip something into one of the small holes of the oil filter (these are the smaller holes or slots that surround the center threaded hole) to hold open the internal rubber check valve of the filter so oil will be permitted to flow backwards thru it.
2) Fill the oil filter with as much oil as it will hold then install it.
3) Connect a tube to the oil pressure sending unit hole on the engine and fill it with oil (I install a funnel in this tube to help with this).
4) Rotate the engine backwards (counterclockwise) by hand and observe the oil level in the funnel/tube. It should go down (get sucked into the engine) as you rotate the engine backwards. If it does not, your oil filter's check valve is blocking it.
5) Once your engine has consumed about 1/2 pint this way, stop. Remove the hose/funnel and install a 0-100 psi pressure gauge into the oil pressure sending unit port. Make sure the engine is filled with motor oil at this point.
6) Crank the engine over with the starter & all spark plugs removed and see if you get pressure to build. You should see at least 20 - 70 psi or so. Once you see oil pressure, you can continue to crank for up to 15 seconds maximum (do not crank the starter for longer than this as it could overheat). Allow at least 1 minute between 15sec cranking intervals for the starter to cool.
Once you build oil pressure while cranking, you are good to go. You can pull the oil filter off and remove whatever you slipped into one of the smaller holes or slots to hold open the check valve. Or you can just leave it in there as it won't get into the engine from one of those ports if it happens to get pushed thru into the filter itself.
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[This message has been edited by Darth Fiero (edited 05-22-2014).]