Air in line ??
I have a 1975 35 ft Gulfstar with 2 Perkins 4-154 engines which for the last 10 years start and ran fine. I run them at least weekly with no problems. About 6 moths ago the port engine would turn over fine but would not start. I bled the system and it fired up and ran good. Kept running both engines at least weekly for about two months.THEN port engine would turn over but not start. This time I just primed the pump and opened up No.1 injector nut till fuel came out and engine started and ran. Tightened everything up again and continued to run engine at least weekly. THEN about two months and again port engine wouldn't fire up. Primed pump and slackened of No.1 injector nut until fuel came through and engine started again. Ran it weekly, all fine, then the other day, port engine would not fire up again. Seems like air getting in somewhere, but where ???
Any info or suggestions would be appreciated as to where to start, or what to look for. I have checked all connections for fuel line, injector pump and fuel pump. Thank you.