Hello (HELP)

I have a 1990 4x4 chevy p/u truck. Truck has never given me a problem. The truck starts and will stay running. When I put it into gear, it stalls. At this point, I've done a complete tune-up on the truck. Still, it starts but won't stay started. It is also sputtering. Any ideas?

Change the fuel filter, if you haven't already done so. Next check the fuel pump. You might not be get enough fuel.