I had a similar problem with my "fuelpump" after driving a while the pump would just stop working and if left for an hour or so it would start working again . To make a long story short my fuelcap sealed to tight and did not let any air in or out causing a vacuum in the fueltank (if there was a breather on the fueltank its not there anymore ).

this might be the case if it is extremely cold where you live. Give it a try and if it works you can buy me a beer if i'm in your country