Fuel line - what diameter for priming pump?

[m1tch]

Hi all,

I have decided to install a hand priming pump to my engine, they are only a few pounds and my OM606 doesn't have a manual pump like earlier OM603 engines. The system is self bleed but I have had issues recently with air in the lines, once I then try and reseal different lines to chase the leak I need to re-prime the system. This is fine usually as the battery is at full power and can crank for ages. I have also recently had an issue with there is air in the lines as well as the battery draining slightly - the car isn't a daily drive. This means that I am sometimes having to try and run the starter motor for ages to get the air pumped out again (there is still a leak somewhere) but this sometimes means that the battery runs down without the car starting. I want to install one of the manual hand priming bulbs onto the inlet pipe so that I can manually pump some fuel from the tank around the system meaning far less cranking.

Just wanting to know the correct size line I need - I believe its 6mm but just want to check before buying one!