Start with fuel. Check the pressure and keep an eye on the fuel gauge after you shut off the engine .On the feed circuit there is check valve that is supposed to hold fuel in and not let it run back in the tank when the motor is shut off.
Then , you could check the pump . Do a current draw ,do a pump debit, there are many things you can look at .
Maybe the pump is very good and you have things wrong

Adrian
'89M///