I have a problem that I thought had went away, but it's back. After my head gasket job, there was two times where after I let it sit overnight, that the injectors lost prime. For the past month it had been fine, but we have been seeing minus 30 Celsius for the past 2 days, and it takes about 10 seconds of cranking before it wants to fire, and runs really rough until fuel fills the lines again. I have closely inspected the high pressure lines, fuel rail, and filter head and cannot find a leak. Any ideas?