I took a new test today with one of my stoves. It was -10 ° C (14.0 ° F) outside. I used alcohol for preheating instead of pumping up the tank and releasing kerosene into the preheating cup as stated in the instructions on the lid. When the preheating was almost done, I carefully opened the valve. The stove began to burn with a beautiful strong blue flame. I did not need to pump up any pressure. No fuel came out of the safety valve either. I think I will stop using the pump since the pressure is good enough.