If you ran three Clines regulators and they did not work but an old one did, of course it has to be the regulators, and not the fuel system. Sorry to leap to the wrong conclusion above. I have had balky Clines that finally worked after pulling fuel thru them-diconnecting the fuel line from the engine and pulling fuel through them.

Mr. Cline suggested this to me at some point and early in the season it seems to jump start them. Probably clears any goop from them. Anyway in my case, that helped.

Have you had your units apart? If you take them apart, watch that little spring and make sure it doesn't get away.