Original post by: Dave ,
I had trouble with the Keurig brewing short cups. It would lose its prime. I found that the model I was using had a very tight fitting lid on the water reservoir. When the Keurig tried to pump water from the reservoir a vacuum was created. The water leaving the reservoir needs to be replaced with something ... and that would be air. The pump was just not able to overcome the vacuum. It worked perfectly with the water reservoir cover removed. I wanted to use the cover so I simply drilled a small 1/8 inch hole in the cover near the back of the reservoir. This is all it took. The air coming through the hole is enough to prevent the vacuum from forming. It's been going strong for over a year.