This is not a "fuel switch". There's no such thing. What there is, is a "Fuel pump relay", but if that were faulty, your truck wouldn't start at all.
The first thing is to check you computer for codes. The information you get from this will depend on the year of your car.
I you don't get any codes, then the place to start is with the ignition, beginning with the plugs and working your way to the coils. If the ignition system checks out fine (including sensors), proceed to the next step:
Your fuel pump could be faulty. The way to test that is with a fuel pressure gauge. You hook it to the fuel rail and take your reading first with the "key on, engine off". The reading should be within specs. (32-39 psi) If the reading is low, it's the pump. When you turn the key back off, the pressure should hold. If not, your fuel pressure regulator is faulty.
If all readings are good so far, then you next take a reading with the engine running. If pressure is low, then you have clogged fuel filter.
Also, pull the vacuum line off of the fuel pressure regulator and check for the pressence of gas. If there's any, replace it. And finally, check all of your other vacuum hoses.