The truck has 110K miles on it. Recently replaced fuel pump (Walbro), filter and pump relay. Ran fine. The other day the truck stalled while idling hasn't been able to start since. I've shot starting fluid and gas into the throttle body and nothing. Once in a while it will make an attempt to start as long as I'm running the starter but it doesn't catch or stay running. Disconnected the gas line to the filter; pumps a steady stream. Has had a new factory distributor installed about 5K ago. Checked the spark. I'm not an expert but the spark appears weak. Its' yellow and does not jump more than 1/4 inch from the screwdriver when I connected to the plug wire to the source of ground. I put in a new coil and nothing. It has always had an idle that fluctuates from normal to almost stalling and than back to normal. Don't know if this has anything to do with it. Cranked it over quite a few times over a number of days; almost fires but will not start. Thanks for any ideas.