Good afternoon everyone. I have been scouring all over the internet in both English and Japanese to find a solution to my problem without much luck. I just finished a rebuild of my FJ20 for my DR30 and finished installing the engine. Upon initial start up, there was 0 oil pressure showing in the gauge cluster and I quickly shut the engine off. Based on my search, here is what I've done to try and diagnose the issue.
The first thing I did was remove the plugs and fuel pump relay and attached a mechanical oil pressure gauge to verify the lack of oil pressure. Turning the car over, there was absolutely 0 pressure, not even enough pressure to fill the gauge's tubing with oil let alone read any pressure. I went through the 30-90 second runs of turning the car over with the plugs out (to lessen the load) to try to build pressure in the system. I was sure to keep the top end oiled manually and watched to see if any oil was coming up top. After about 6 times, I saw no difference in oil pressure and no oil coming to the cams.
The next thing I did was remove the oil filter and filled oil down the center channel in the block to add oil to the pump. The pump upon assembly was filled with pretty thick oil by the machine shop to properly prime it before install and I read that adding a bit more through the oil filter neck could help kick start it. At the same time, I checked to make sure the relief valve had no cracks and wasn't stuck. I tried the same process of turning it over for several tries of 30seconds+ with no pressure built.
Next, I read that a common reason is a dented oil pan or oil pickup strainer. I lifted the car and did notice some sizeable dents in the oil pan and decided to drop the pan to see if that was the culprit. With the pan out, the strainer's mesh was in fact dented in a bit and the dents in the pan looked rather bad. I repaired the mesh on the strainer's original shape and banged out the pan to no longer have the dents. I also checked the pressure regulator valve in the front cover while it was out to make sure it hadn't come out and that it moved properly with the spring. The regulator valve was fine and the oil strainer had no cracks or issues aside from the dented mesh. The gasket was also brand new. I put everything back together and filled it with oil and tried the same process of turning it over with the plugs out but still built absolutely 0 oil pressure. Frustrated, I started the car and ran it for about 10 seconds to see if it'd build pressure that way since it wouldn't do it with just the starter. Still nothing.
The oil pump ran fine before the rebuild and the engine was ok prior to the rebuild, I pulled it just to refresh it. I'm really trying to avoid having to remove the head to get the front cover off to physically check all the oil pump's clearances again so any help or guidance is much appreciated. I'm at a loss for what could possibly causing it to get absolutely no pressure at all. I added some pics below of the oil pan dent and fix and the page from the engine manual showing the different places to check. Please help!
Sounds to me like the oil pump still hasnt primed, once it starts cavitating it'll never suck any oil from the sump. I had a LS1 that was doing the same thing after a freshen up. We pressurised the engine by putting some compressed air in through the dipstick tube while blocking the breathers, and then starting the engine.This forced oil up through the pump. Even before starting we could see the oil coming up the clear hose to the autometre pressure gauge.
I usually prime the pump with vasoline but I didnt bother with that one and I bit me in the ***