2000 sierra 4.3 wont stay running

[dsmobileautorepair]

2000 sierra 4.3, turn key on have 60 psi on testor, you can hear the fuel pump run for 2 secs, then gauge drops back to 0, when running, it bounces between 48-54 psi, then dies, wont stay running, just did recent full tune up, ac delco spark plugs, new wires, cap and rotor, truck has been down since day b4 thanksgiving

[ProTech]

If the pressure drops down to zero, then you definitely have a problem somewhere in the fuel delivery system. You'd either be looking at a bad fuel pump, or a leaking fuel pressure regulator. The regulator is located inside the upper intake plenum, so that would need to be removed to actually be able to see if the regulator is leaking.

More than likely though, the pressure is just backflowing right back through the pump. I've seen this quite a bit, but also have seen plenty of regulators go out too. If your truck has a return line, try blocking it off and see if the pressure holds, then you'd know it is a bad fuel pressure regulator. If it still drops with the return line blocked off, then the pump is bad.