Gremlins? Voltages and relays

I have a 2012 Volkswagen Jetta TDI automatic but I bought with a blown engine swapped in the new engine only has 40,000 miles on it on the way I can get it to run was by bypassing/(wired in my own relayfor power} the fuel pump that's right next to the injection pump I wasn't getting any power there or I request to turn it on I've looked and searched cannot find the specific relay for the fuel pump I know where the relays are at under the hood and under the dash I don't know specifically which one the fuel pump relay is I've also noticed that the AC compressor is only getting 8 volts. Other issues I have or old saying fuel pump circuit open control pressure circuit fuel temperature and secondary coolant sensor High. Somebody can point me in the right direction for the relays I could at least start with that. I also didn't know if this system has a control module for the specific function of the fueling or AC. Any help on the wiring diagrams relays were specifically to Jews would be greatly appreciated

I also forgot to say that the car seems to be in limp mode also it only will do 3,000 it does not want to shift correctly I mean we shifting it like and slowly get it up to like 55 but I mean we're talking like three quarters of a mile

Did you scan for codes?
Post them please.

OBD works, you need to start there.

The compressor is controlled via a duty cycled solenoid. It is not just ON or OFF. So 8v may be normal (no idea, that is not how they work, so that is not how I would diagnose the system).

I believe both the J49 and J17 fuel pump relays are inside the car in the upper part of the E-box.

I *think* J17 is what controls the V393 transfer pump under the hood. That relay is in the very upper right of that relay box, you may have to pull the knee panel down to access them all. I have never seen one of those pumps go bad, nor have I ever seen one of those relays go bad, so I am not 100% sure on its location.