1987 560SL will not start cold

[kubotamanl48]

560SL will not start cold, if you remove air cleaner and keep priming with a little fuel it will start and run great. It will continue to start and run until it sits for several hours and then I have to prime it again. The fuel pumps seem to be working fine. There is a component called a "start valve" or "cold start valve" in diagram I was reading. It has its own fuel line as well as the 8 that go to the injectors. Could this part be causing the malfunction and how do I check it?