1991 s-10 Blazer

Here are the symptoms: hesitating, spitting and sputtering, feels like it is going to stall when ideling. This only starts once there is about half a tank of gas. This is my sister in laws blazer so I have no engine info or other infoe. They have put new plugs wires, and cap, and problem persists yet. Have also tried dry gas thinking it may of been a bad batch of gas. Any ideas?

Sounds like a fuel pressure problem possibly caused by a faulty fuel pump. It is probably the pump in the tank rather than the in-line pump. When the pump in the tank does not work properly or at all, the in-line pump does not make enough pressure (approx. 7-9 psi) for the injection system once the fuel level falls below about a 1/2 tank. The tank pump helps keep the in-line pump primed to maintain constant pressure. It is quite a job to replace though. The tank has to be drained and removed. Good luck!!