BEfore you start it. Our oil pumps are self priming, so all you have to do is pull the fuel pump relay and crank the engine to build oil pressure. I however, didn't build any oil pressure at all after 10 minutes of on/off cranking when I installed my 3L. The oil didn't even make it to my oil filter (1st port of call so to say) and so I made a contraption to force oil back to the oil pump (using air pressure from my compressor) to help prime the so called "self priming" oil pump. Then I built up oil pressure after 3 seconds of cranking.