As above really. Unscrew the little retainer all the way, give it a little press to 'unstick' it, then make sure the coupling of the track pump is fully on. From a starting pressure of about 80 or so, my tyres are usually up to my preferred 110 psi within about half a dozen full strokes of the pump. Having said that, I did have a faulty valve on one of the tubes which wouldn't properly pop open during pumping, so the tube had to be replaced.