I've been having problems with my shurflo's in the cold and I'm not sure why. I used them for several years for vacuum and now to move sap around the the sugarhouse. What's interesting is that I've had to keep swapping out the pump that I use to move sap from my main tank to the feed tank. For what ever reason, if I leave the pump out, even after draining it, it doesn't pump but if I bring the pump inside, it works just fine. I'm wondering if the diaphragm is just getting too hard not being wet and so it doesn't move well to create a vacuum. In any event, that's what I've been doing.
That being said, yesterday was a rough day trying to boil between a high temp of 17° and the wind. I'm glad I wasn't boiling outside!