I'd add that when you put the new molex pins into the plug you need to pay attention that they go the right way around.  The little metal tang that sticks out the back of the molex crimp terminal is keyed to fit into the plug housing to stop the crimp terminal pushing out the back of the plastic plug as the plug and socket are connected. Not the best explanation, but have  look and a think and it should be easy to work out. The tang would be visible on the bottom side of the assembled plug in MartyJ's picture.