Have rebiult my 4.0 V8 and despite all new components just cant get any oil pressure on crank over. I removed cleaned and replaced the oil pressure releif valve and fitted a new set of oil pump gears properly lubed with vaseline and engine oil, was no wear on the old gears ( it must have been replaced at some point) have spent thousands on trhe motor and dont really want to start it till I know I have pressure. I pumped oil down the oil sender hole which seemed to end up just going straight to the sump as the level on the dipstick rose.... any ideas on what I can do without pulling the front off the motor and lowering the sump would be much appreciated..... am using a mechanical oil guage that connects into the sender hole.

Many have suggested its difficult to get oil prtessure on cranking and I should just start it?

Cheers

Crank it without the plugs in - should turn over a bit quick which may or may not help. Watch out for spray out the plug holes.

Rich

Have been cranking with plugs out and removed oil sender ... still no oil.

Ok well after all sorts of advise, I created a pressure vessel that I had about 350ml of oil in ( it was an old small halon fire extinguisher bottle) put 60psi of air into it and had a valve on the other end , I attached it under pressure to an extension hose I have off the oil pressure sender outlet ( it actually has a tee with the sender in it an the hose comming off for a VDO pressure sender). I cranked it over and had somone open the valve to allow the oil to flow under pressure into the tee where the oil sender is and walla while cranking the oil light went of for about 2 seconds. I reckoned it could get pressure just cranking wasnt fast enough so connected the ECU put trhe spark plugs back in an fired her up it took around 8 seconds for the oil light tyo go off now at 2000rpm I have about 4 bar which I thought was a bit high... i.e 58psi... anyway engine runs so will need to add some cam additive and run it for 30 mins at around 2-2500rpm then oil an filter change... onto the next few steps...

The concentric rotor pump can take forever to prime. Sometimes better to leave the oil filter empty so it can vent any air into the element space.

Ours took 3 starts and 10 second runs to get oil pressure up after a rebuild with a new short engine.

Peter

I think that may have been the issue I had filled the oil filter so it would have had a job to get the air out.... Many Thanks