cold weather air in fuel system

I have had 5 volvos, all cummins powered,ranging from 2002 to 2004. All but one have had air sucking into fuel system in cold weather, 5 degree fahrenheit or colder shortly after startup. All have davco 382 fuel processor, where you can see air swirling in the fuel. Usually pull to side of road and after 10 minutes or so of engine bucking and dying, stops sucking air and runs fine. What makes it difficult to diagnose is last only short time and often below 0*f when occuring. Re-o-ringed the fuel processor on one 2years ago, seemed to fix,although no super cold weather last year here in the northeast U.S. To know for sure. Now the problem has started again. My question is do the fittings on the plastic fuel lines have o-rings that need replacement or is it likely the davco fuel processor needing re-o-ringed again?