Its the one on the BK side to the CFWC. sometimes it doesnt want to pump. or it will start and quit in a few seconds. I tried lowering it but still has the same problem. i think it might be cavitating. i ordered a new impeller from Morebeer hope it corrects the problem. anyone else ever have this problem?
I’ve been having that problem - just today I turned it off and turned it back on and that fixed it. Must be a windows OS pump 
Sometimes I burp the fittings to let air out, that seems to help.
Have you seen this thread about pump head orientation?
http://www.homebrewersassociation.org/forum/index.php?topic=11157.0
How hot is the liquid you are trying to pump? If it is boiling, cavitation is likely the issue. The new impeller is a definite improvement. But lately, I don’t recirculate during the boil. I just hit it once the flame is extinguished.
Thank you so much for directing me to this thread. I have installed the new impeller and changed the orientation and Seems to work. Next test is to try recirculating with boiling water. My goal is to get enough flow to create a whirlpool in the BK while pushing the wort through the CFWC.