ive got an aquamedic ocean runner3500 that came with my second hand aquamedic 5000 shorty skimmer about 6 months ago. ive now got to the point of starting the skimmer up on my system but the pump wont work. i think ive read somewhere that when starting up after being off for a while they might not always start up. im not sure if im imagining this or it can be the case. if so how do you get it working again?