Kstorm

Hey guys,
I'll preface this by saying that Im rather new to working on my own cars, so I've hit a brickwall.
I bought a 94 3vze 4runner a few weeks ago. We drove it back home with no issues. The next day I started having starting issues intermittently. It always cranks, but has a hard time starting especially lately.
It would sometimes start after a jump (even though the battery was showing 12v + before jumping everytime) other times it would t start on a jump but would with a pop start. we found a disconnected ground wire from the battery and i replaced it. It then didnt start with a jump or with a pop start.
Cel would come off and on, pulled the code and found it as 52.
Decided to check my ecu and cor. Found a leak that ran down that area, sealed everything up bought a used ecu and cor. (Before replacing it qould start about 4 out of 5 times by jumping Fp and B+).
That day the cel codes still read 52 and also a 12. Ive heard this is likely a knock sensor issue, but that shouldnt cause a no start right?
I also bought a new efi relay and pulled out the killswitch and wiring.
Today I took it out, it was running rough but it did start after a jump and i got it to my work, after about 30 min of driving it seemed to level out.
I went to start it again a few hours later to find it not starting again (still cranks). I checked my cel codes again to find that it now is reading 12, 22, and 52.
I cant hear the fuel pump turning on, even after jumping Fp and B+. Jumping it is not making it work, not in an area to pop start it.
My next idea was to try looking for any missing grounds, and to change my fuel filter, but looking for some advice before I go insane.
Much appreciated!