If you have a built in winterizing system that utilizes the on board pump and has a connection inlet for winterizing, make sure the hose connection has a good rubber gasket and is tight. If you have the slightest air leak at the connection it will likely not suck the pink stuff in.
On mine the screened hose gasket was too thick to allow me to get a tight connection. Replaced it with a thinner non screened gasket and solved the problem. Mine seems to start pumping faster if I open (on then close) a low point drain first to get it started.