with the ignition switched on, heard a "thunk" in the engine compartment which I assume is the fuel pump turning on, then went to the "schrader" valve on the passenger side fuel rail and pressed the valve in and no fuel came out. what might the problem be? Any suggestions?

Steve

 

Did this cause the motor to not run or anything?

I am guessing if you had no pressure on your rail, your pump is out, or, something is stopped up.

I guess a little more info is needed, to, make an educated guess online. I would think that there would be fuel there, if, the pump has supplied the rail with fuel for the initial start up. With the amount of pressure these things put out you should have had a gyser on your hands. Was the key still on when you pressed the valve in?

Just my input.

 

no gyser..... just a little dribble. and the key was on (position just prior to engaging starter. Additionally, the truck ran fine 6 or 8 weeks ago. Then it hasn't been used until the other day when someone wanted to borrow it and it turned over fine, just wouldn't fire unless I sprayed fuel into the the air intake above the intake manifold. then it ran for a couple of seconds until the fuel was gone.

 

OK, sounds like to me your fuel pump is out then, or, your fuel filter is cram packed. If you are getting a dribble of fuel to the rail, then, I would have to say the pump.

Also, what year truck is this. I had an 88 that had 2 pumps. One in the tank and a high pressure one on the frame.

Hope this helps.