Is it possible for a car to run with only the main fuel pump if the in-tank pump does not work?
Probably. Many have reported difficulty when the fuel tank is less then 1/2 full if the in-tank pump is faulty. Also, there is a small stepped rubber hose between the in-tank pump and the outlet pipe (all inside the tank). If that small hose is faulty it can cause difficulty when the fuel level drops below 1/2 full.