On your gasoline engines, perhaps you're getting moisture into the distibutor cap, which would give you starting problems. I remember this happening to my Mom's Toyota when I was a little kid. The mechanic took off the distibutor cap, coated the inside with gasoline, then lit it with a match. That must have eradicated the moisture, because the car started right up. However, I'm not advocating this procedure, mind you!
'84 300D Euro