Im flumoxed

[Jules-C]

Just out of interest.. what tells the fuel pump when to come on and off? And how does it decide when to be on and off?

Mine ticks away when the ignition is first switched on. I assume filling the carbs, but what tells it to stop? Is it constant speed or variable? It's one of those things I've never taken the time to understand.

Sorry to detract from the original post.. although on topic. 

There is a pressure switch built into the pump that switched it off