I recently aquired a beer engine and in a rush to get ready for a party I got a check valve and connected it to a de pressured corny ready to go
but to my horror it wouldn't pull properly I would pull and get nothing from the pump till it was about half way through the stroke
after struggling with it taking 4 to 5 pulls to fill a pint I assumed the seals must have gone and I would need to look into it
but yesterday I was about to dismantle it to have a look when I noticed the beer line from the keg to the check valve didn't look right I gave it a check and found that it was only in the fitting a quarter of an inch pushed it in properly and now it works perfectly