Been having this problem for years and I'm over it.
Have an FJ20 with external oil pump. The pump is mounted slightly higher than the sump and it has a -10 oil feed line to the front cover where the internal pump used to be.
Each start up, it rattles it's head off until oil pressure comes up.
My solution is to set a start delay in the ecu until it sees oil pressure. Problem with this, it takes ages to start each time as the longer it sits, the more prime it looses.
I looked at an accusump as a solution which would of course work, but are there any other fixes?
I've been looking at small electric oil pumps that i could fill the system with first but nothing seems specific for the problem.
Any suggestions would be great.
Thanks