Water Pump Lost Suction??

I've always winterized my water system using a "T" valve that lets me pump RV antifreeze direct into my water system from the antifreeze bottle and I have never had any problems doing it this way, However, today I started to winterize and I first checked if the water pump would pull water from the on board water tank. It did. I then changed the "T" switch and it pulled about a gallon of pink RV stuff into the line. As that gallon was running out, I then switched to another bottle and the pump would not pull any more fluid. The pump is still running and vibrating and sounds normal. After several tries, I changed the "T" switch back to the on board water tank, just to see if the pump would pull water from there. It would not! I believe that I have been told that these pumps can "loose" their prime and stop pumping, like mine is doing. Is this true, and if so what steps should I take to make mine re-prime itself. I have a standard SureFlo pump.