Ford Windstar 1996 3.8L V6 Fuel system problem.

After standing overnight (or sometimes less time) the fuel pump "hums" for as long as 90 seconds, after which something "clicks" under the hood, and the car starts immediately.

It will run at highway speed, under load, with no hesitation. Gas mileage is typical for combined city/highway driving.

Mechanic #1 said I need a new fuel pump. He "showed me" that the fuel pressure was low by taking out a plug at one cylinder of the intake manifold (engine just turned off), gasoline squirted out when he put a nail into "something inside." He says the amount of gasoline which came out was not enough, but would be happy to measure the pressure at a auto parts place. He said his guage was not working.

An auto parts salesman said he'd be very surprised if the fuel pump was defective if it provided enough fuel for highway speed driving (70 MPH), both up and down hills. He didn't know if there was a backflow preventer (check valve) separate from the fuel pump, but I should try to determine if this was the case.

I don't want to spend >$400 to replace the fuel pump if it won't fix the problem.