I had an awesome reliable engine that ran in any situation. I found a car with a body and paint job that was much nicer and the car had less electronics in luxuries, so I switched engines because the engine in the nice looking car had much wear and tear. After swapping engines the car won't start after running the first time for about 3-5 mins. Just turns over and I get nothing. The only thing that happened after it ran the first time is the fuel tank was dropped and checked for loose contaminates. Is there a problem with compression or what. Where do I troubleshoot first to find out the problem. I heard from someone that oil pressure and fuel pressure has to be just right or you get nothing. This is what I am dealing with and how much info I have to go further on...

Please help!!!

is your engine getting fuel? Have you checked your fuel pressure? I would start there.

Also double check all electrical connections.

Do you have access to VagCom?

good advice there, is there any fuel in the tank?? do you have a spark at the plugs?? are all the air pipes on tight ( fuel/ air/ spark ) = a start