Ghost in the machine!

I have a 94 chevy pu trk 1500 2 wheel dr.last week it would not start, the engine turns but will not start. Of all places a gas station first of all I thought it was trouble with the gas(no problem before) then i poured some gas in the thottle body and it turned over. Bad fuel pump it must be right, well I called a tow truck and when the guy gets ready to tow the truck It starts like there was never a problem? then one week later it does the same thing I was driving parked the truck about 1/2 hr. later I go to start it and the engine turns but will not start I sprayed starter fluid down the t.b. starts for a few seconds and stops. So I called again for a tow trk. ,When he gets there I show him it turns but will not start .He picks up the front and gets ready to drive off and I said wait a minute one more try and you guess itmy truck starats up like no problemo . what could this be I replaced fuel filter by the tank ,dist. cap & rotor. was it picking up the front end, or something .Or did putting the truck in neutral have something to do with it.( 3 sp automatic) something Electrical or trouble in the tank with the fuel pump. Open for suggestions !!!