2002 e150

runs for how lond 1/2 second or 5? hows the fuel system FILTER?

runs for about 3 to 5 secs then dies. checked relay and it's good. got fuel pressure

Usually has to do with fuel. Have someone starting the truck, and with you out by the throttle body with some starting fluid, see if the engine will stay running with a little squirt of starting fluid. If it does want to stay running, you would want to verify the fuel pressure. Should be somewhere around 35 lbs. Pull the vacuum line off of the fuel regulator also to see if it stays running, and take note if you see any fuel in the vacuum line. Things to look at would be the fuel filter, and there is a fuel strainer at the end of the fuel pump in the gas tank. The thing is to check it, you may as well replace the fuel pump also.

Mine was the distributor,, it would run for 5 seconds up to 1 or 2 min,, then die, turn key to off position and back to start and start right up for 5 seconds up to 1 min then die, then if I didn't return the key to off position but try to restart form the on position it wouldn't start,,and wouldn't have spark,,until I returned it to off position,, and over and over again, if this sounds like your problem,,,REPLACE YOUR DISTRIBUTOR