For those who don’t have access to vcds software to prime the secondary fuel pump. 
 
Simply turning the key to the on position only powers the sending unit. It does not power the secondary pump which supplies the cp4 with fuel. It either needs to be turned on via vcds software or to jump the pump manually with 12v. 
This harness makes it simple. Just unplug the pump and plug in the harness. Run the harness directly to the battery. Can’t be easier than that.