I am attempting to change out my sprayer on my sink and can't figure out why it doesn't have constant pressure?? I depress the sprayer but it just sprays and quits and I lose pressure, any thoughts??

Whilke it could be a problem in the faucet mixer I would start by taking off the sprayer end on the sprayer and cleaning the aerator. You could also disconnect the entirte spayer handle from the hose and see if you get a full stream of water, if no the problem is in the mixer, if yes your sprayer screen or aerator is clogged.