High Pressure Fuel Pump

Hi All

I have a 2009 Astra Twin Top z2.2ah. The High pressure fuel pump failed and I didn't feel like paying $1300 for a new one so I got a rebuild kit and disassembled pump and replaced the three diaphragms. I used the reassemble in bowl of ATF oil method to fill it and i wasn't real confident with this method but it worked. For approx 2000km and it failed again.

I took it apart again and it was full of petrol instead of ATF oil. This time I assembled dry and removed the cap and pressure bulb (not sure of it's official name) and filled through that hole.

My problem is that I failed to take note of which way the bulb went 'inny or outy' . Checked videos online and they vary as to how it goes.

I put it in bulb facing out. The pump works but I have noticed a fine weep of ATF from the hole in the metal cap that covers the bulb.

Has anyone had any experience in rebuilding these pumps and is there a obvious reason for the pumps filling with petrol and the oil leaking out even when there are no holes in diaphragms?