Just reinstalled the L24 in my 1972 240Z after refreshing it. By that I mean remove carbs, intake, exhaust, timing cover, etc. to clean them up, repaint the block, then reassemble. I did not touch any internals of the engine or head. The car ran perfect when motor was pulled a few months ago. Now I can't get the oil to prime. I'm using a new high volume "turbo" oil pump that does prime itself with a screw driver. But using a long tool to prime the engine (counter clockwise) the engine will not prime. I've also tried packing the pump with petroleum jelly but no luck. Both the old oil pump (which was working just fine) and this new pump do the same thing: no priming of the engine. Oil pan has 5.5 quarts of oil. The only thing I can think of is the pickup tube is not air tight. But before I pull the oil pan, anyone have any ideas to check first?

When you write "won't prime" do you really mean won't pump? Filling it with oil is actually the priming.

How do you know it's not pumping? Oil flow to the cam shaft, reading on the gauge, or what?

You might remove the oil pressure sending unit and see if oil flows from the hole when you spin the pump. Also, if you packed vaseline on the inlet side of the pump it might have trouble pulling the oil in to pump it. You can only generate atmospheric pressure on the inlet side.

What about pulling the valve cover and see if any oil is making it's way up to the cam? If you try this don't put your drill on HIGH when spinning the distributor/oil shaft. I learned that the hard way.

I mean the pump will prime itself before installation, but it won't pump any oil in the engine when installed. The valve cover is off and there's no sign of oil movement, even at full drill speed (I tried that - lol). The original 240Z gauge does not move.

I may try pulling the oil sensor out and push some oil into the block's internal passage that goes to the pump. That's where the pump pushes oil to first, correct?

One thing that just came to mind is the oil passageway plug that goes into the front of the block. I remember pulling it out and looking at it but am now only 80%ish sure I reinstalled it. I'll check my workbench when I get home from work. Would that affect pressure?

I did replace all the freeze plugs (except rear of block) , but none of them plug any oil passageways, correct?

I can remember reading about a head gasket that covers one of the oil holes but that's about all I remember. I wish you the best of luck how ever it turns out.

Pretty sure I remember reading about people using the oil pressure sending hole as a source to prime the whole block with oil (might have been @Captain Obvious , although not obvious). So, if you can rig up a way to push oil in that way it should fill the system.

I am not personally familar with that plug, it should be described on the Monroe Rebuild book, but it does look like it matters if it's the one end at the end of the main passage/gallery/galley. If it was left out, the oil would not get very far after it left the pump. There would be no pressure build either.

One of those borescopes would be handy.