I have a 1995 GMC sierra with the 6.5L. I am having a fuel issue that was mentioned once before in another post. After some investigating it was determined to be a faulty oil pressure sending unit. The lift pump was not working as a result. Unfortunately, after replacing not only the lift pump, but the sending unit I still have no fuel coming from the petcock when idling, and when petcock is opened she wants to shut down. I have a feeling it is a wiring issue but I am not very good with electricity (we don't get along very well lol). The reason I went investigating in the first place was when the truck is shut off (regardless of temperature) she will start for a few moments and then shut off starving for fuel. After priming the system she will start and run fine. Also at high RPM she was missing a little making me believe the sending unit to be faulty. Any suggestions would be helpful. Thanks:)

if the tank is low on fuel drop the tank and check the pick up sock in the tank

Just went through this last year. Check/replace fuel lines. Your fuel level sender lines might be corroded to the point that they suck aim too. About $90 for the new part.

Look for the 'snoot in my stocking' thread complete with pics.

Take the supply pump off and blow back thru the tank with the cap off. Think the sock is stopped up.

I have run through couple of the scenarios that have been mentioned and they seemed unlikely so I did a little more investigating and have found no power getting to the lift pump. So I back tracked to the oil pressure sending unit and that was getting no power either. It seems to me that I may have some sort of wiring issue. What is the source of power for the oil pressure sending unit?