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Q: Fuel pump

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My 2001 Buick Century won't start. The gas gage floats so I've ran out of gas a few times, the last time I did which was 12/28/16 it wouldn't start back up. I. Assumed that I may have needed more fuel so I put a couple more dollars worth of gas in the car. It started and ran long enough for me to make it home and that's less than 4 miles from where the car was parked. Once I got the car home and turned it off it no longer started back up. I asked a buddy if he'd take a look at it, he suggested a new fuel pump so I've been doing some research and realized it could be a multiple of things such as fuel filter, or the fuel pump relay. I'm curious to know if there is a way for me to know which it is for sure before I can get a quote or spend to much on a needless part and labor.

My car has 170000 miles.
My car has an automatic transmission.

Immediately upon turning the key to the "on" position (NOT start position), you should clearly hear the fuel pump in the fuel tank momentarily "whirrr" as the pump pressurizes the fuel system. If you don’t hear the pump "whirrr" momentarily, there is either no power to the pump or the pump is dead. It is easy to check for power to the pump using a voltmeter. Using a voltmeter, if there is voltage all the way to the pump terminals, but no pump action, you need a new fuel pump. Running the tank dry possibly complicates the diagnostic because even if the pump does run, because it has been run dry the pump impeller seal can get damaged thus rendering the pump unable to suck up enough fuel. This means that even if the pump runs, you might still have to test the output of the pump and the pressure in order to be able to rule the pump in or out as the cause of the no start. Whether the pump runs or not, you could try spraying starter fluid in the intake while you crank the engine. If the engine momentarily runs, you know there is a fuel supply issue and that could be the pump, the filter, the injectors, the injector wiring, and even a faulty engine coolant temperature sensor which sensor is quite essential at start up as it is the only means for the PCM to signal the injectors that the cold start mixture must be enriched. Really, the fastest and most efficient resolution will be obtained if you schedule a hard or no start diagnostic. Working around fuel is quite dangerous and this is best left to a certified mechanic. Also, such a diagnostic, and indeed the required repairs, no matter the scope, will be quite economical on a mobile basis from YourMechanic.

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