Don't open up the pump mate - it's not really a 'user servicable' item...

Is yours the standard spec pump or the race version?

I know with my race version i have to stick the odd drop of methanol through it to keep it lubricated...

Have you checked for blockages in the pipework and the water filter etc.?

Tim's spot on though - you do need a good power supply when priming the pump.

Hope that helps...