I have rebuilt my valve block and replaced my compressor. Manually activating the pump via the ECU plug pins 1+8+26 - air is not reaching the tank as after 5 minutes I can remove all air lines without any sign of air loss. What valve needs to be checked directly after compressor / air drier and what path does it take? I wish for it too work as to manually test each air spring valve manually via pin 10+11 and 27+28. Thank you.