Hello,
I have tried the search but come up with flooding problems and grounding problems but have fixed those.
Problem:
I installed an engine from a S5. The front cover was swapped. Basically S5 short block but all the S4 accessories placed back on. I am able to get the engine to crank but it will only do so when hooked up to a running car. I tried with a new battery but when the key is turned past insertion, the car dies. There is no clicking, lights or anything. When it is hooked up to a running car, the gauges work and it is able to crank over but will not start. The grounds were reinstalled on the starter and firewall. I am guessing it is a short somewhere. Any suggestions?
Thanks

 

A short would pop some fuses, so check them out. Test both the underhood and interior fuses with a multimeter, then re-check all of the wiring around the engine.

 

I'm not familiar with electronics/wiring. Should I be looking for blown fuses or testing all of them? None were broken/blown. I've also gone over the wiring but will check again in the morning. What would allow the engine/electronics to respond when being jumped but die when trying to start/no response by itself(when using a new battery only)?