Problem: When cold, engine starts and runs for a few seconds, then quits. Starting procedure, turn key till all green, then turn key to hit starter and engine starts right up. No problem here. But engine quits, after a few seconds. This problem started a few months ago. I have to wait for a couple of minutes then crank the engine a few times before it will start. Then is runs normally. No puddles under engine, so no leaks. Sounds like I have a air lock, but not sure. That is way Iím asking for help. All maintenance has been performed. Unit: Gulf Stream SVB, Engine is a 1999 Cummins 275hp.