I have a 1996 F150 4.9L FI. Truck has been starting great and running fine since the day I purchased it. Now, just yesterday, I started her up and drove up the road, parked for a couple minutes, and it would crank like it was fuel starved. Finally, I depressed gas pedal completely, and it started up (almost like it had flooded out) - ran perfectly on the way home. Turned off ignition, and had to repeat above to get her to crank. After sitting awhile, I can go out and start her up just fine. Noticed a few cracked vacuum lines and replaced (no effect on issue). Lastly, I did also notice that even after it's running fine, there seems to be some lag in RPMs settling down after reving it up a bit. Any idea of what to check would be greatly appreciated. NEW to this forum (just now getting on the net and researching things like this). Thanks for any and ALL advice. Whitey

 

Get yourself a fuel pressure pressure gauge, and lets start with some baseline measurements. Hook up your gauge, start the truck, let it idle and check the fuel pressure and note it. Then pull the vacuum line off of the fuel pressure regulator, now check the pressure and note it, also when you take off the vacuum line from the regulator, look for fuel squirting out of the regulator. Come back with your results, lets see where it sits, if we need to do more tests, we'll prescribe them then.