[Elbert]

I think you have found part of your problem! Fuel pump relay = what controls the fuel pump. You need a shop manual for the year model truck your engine came from. You may find some info on that online but I would at least go by your local book store and pickup one of teh not so good haynes or chiltons manauls (better than nothing) or go to helmic.com and get the GM manual. I think on the year model vehicle your engine came from.... a code reader is a code reader....not to much info come from the ECM. If you have the $$ you might want to get an automotive scanner tool... I don't know what to advise you on brands as to a reasonablly price one that does a good job, other than to say that the OBDI stuff, you don't need the sophisticed scanners like you do on the newer OBDII and whenever OBDIII comes out.

The bottom line..... you may simply need a new fuel pump relay!