My 1994 Sentra just won't start because there is no fuel in the line from the fuel filter. The fuel filter is new (change as it might have been the culprit). The fuel pump makes a whirring sound when trying to start the car. It actually pumps out gas when tested oiutside the vehicle. Was told to check the fuel pump circuit. How do you this? How do I check for voltage on the fuel relay connector? How would I know if the fuel relay is aready bad? How do I check for volatge on the wiring harness that connects to the fuel sending unit? Meaning where do I connect one probe and the other of the tester? The first mechanic said it is the fuel pump that need to be replaced, but the fuel pump is pumping out gas when tested so I am hesitant to buy a new fuel pump (which is expensive!). Is it really the fuel pump not working as specified? Thanks a lot.