I have a 1985 f350 with 460 v8 engine. The problem I'm having is can get it to start for a few seconds then it dies. I cannot get the fuel pump(s) to come on by disconecting the wire to the starter relay, turning the key to start and listen for the pump to come on as described in the Haynes repair manual. I suspect that there has been a long standing problem in that if the truck sits for a while, you have to pump the gas peddle rather significantly to get it started but it ran. Now it dies immediately. I have replaced the front tank fuel pump, blown out the gas lines, verified that the tank selector switch and valve functions, gas in the tank and oil in the engine. I would love to hear any suggestions as I'm about to start tracing every wire in the fuel delivery system and I'm not looking forward to that. Any help will be greatly appreciated.

-Roy