can i replace the oil pump in a 2g gsx without pulling the engine?

If it has balance shafts still, it will be a major pain. It's easier with the engine out, but can be done.

More to my concern, why do you want to just replace the oil pump? If it had an oil issue, likely hood is it needs more than just a pump replacement.

put motor in and started up but have no oil pressure. pulled plug at passenger side of head to check oil pressure and there is none.

IF that motor started and RAN without oil pressure, then you do have other problems that will need addressed. I would pull the motor and check all bearings and hope my rings didn't get too hot without oil. Those are 2 major things, but dry valve guides are bad, dry rockers, etc. are also possible with oil starvation.

Assuming you have a 4g63T engine, first check if the oil relief plunger (04211 in picture) in the oil filter bracket (housing where the oil pressure sender and oil pressure switch mount) is not stuck/damaged. It is behind the relief plug (04181) next to the oil pressure sender. It controls the oil pressure. Should also test oil pressure at the oil pressure sender (put a oil pressure tester gauge where the oil pressure sender is).

tumbler said:

put motor in and started up but have no oil pressure. pulled plug at passenger side of head to check oil pressure and there is none.

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How long dis you start it? Did you prime the pump? Can you prime it now or have you tried?

When starting a dry motor or a new oil pump you have to either pack the oil pump gears, or prime the oil pump. I have came across this with brand new build and new pump that neither was done. The pump never pulled oil or primed its self. I ran a fitting to OFH and forced oil in threw the pump and it then worked as should.

Priming the oil pump: https://www.dsmtuners.com/threads/h...h-timing-components-already-installed.286487/