I just found out that the fuel pump is going out on my 1988 Bronco. The problem is, Advanced Auto told me there was just one and now I've learned that there are indeed two. Is there some way to tell which pump is going out? You hear a high-pitched whine when you are driving, so I would think it's the external one.....?

 

Do you hear the whine constantly? i would guess it's the low pressure pump... but i´m not sure at all. Anyway if you take the tank down, i would recommend changing both units... It would be a shame to have the other one fail just as you replace the first one...