I have a 95 F150 with 5.0 engine. The engine will start, run smoothly for approx. 3 seconds and just shut off. You can hit the starter immediately after it dies and engine fires right away. Runs 3 seconds and shuts down. Any ideas where to look?
Thanks

 

If you have access to a fuel pressure gauge you could see if you are losing fuel pressure. What you can try is to spray a little carb/choke cleaner into the intake when it starts to falter and if it continues to run while spraying there is a fuel supply problem.

 

I bet you have a weak fuel pump. I don't know if you have duel tanks or not but if you do then I advise you to switch tanks and see if it runs like a scalded dog

 

Easy test is to 'ground' pin 6 on the DLC (data link connector) and see if it continues to run. It helps to diagnose a PCM timed grounding control/run dropout. The pumps are commanded to run to pressurize the system with a short grounding of the relay to close the active fuel relay and allow power distribution from the relay out through the inertia and on down to the tank.

You can also pull the fuel pump relay and check the connector face for the needed circuits as well.