is it gas or diesel? Fuel pumps work or just give out, so need to know what it is and year. Just had to install fuel pump in our 12 E450, but suspect the pump was good and the frame mounted relay was bad. Had issues like failure to start, start no power, hung starter. Fuel pump for the V10 was $500 with another $1000 to install. Relays can be found for $70 to 250 depending on where you get it from.
your 1st post says gas, 2 post refers to a cummins so not sure of what you are dealing with. So when asking need to post year model and engine for best results. Older cummins pu's did have fuel pump issues as they didnt have a lift pump only the tank pump.