I know what you mean by getting frustrated and wanting to come back later. I work at a pharmaceutical in Memphis as a process mechanic which means I spend a lot of time on call in duty on weekends. I had one saturday night in which I got called in at 1 am and when I got there they said a pump had went out, so the first thing I do is tear the pump down and check the diaphrams, they look ok so I tear the entire pump apart and put it back together and the pump makes two cycles and quites so I spend another hour taking the pump apart and putting it back together. This time the pump makes two cycles and quites again, that's when you reach the point where you just want to get away. By the way my problem ended up being a blockage downsteam from the pump.