I am new to the group, my name is Willie. i have a 96 F-150 4.9 with 219500 all original and running strong. common codes are 171 &174 those are daily which i have replace some items (o2 sensor)
but it runs great.
I keep both tanks full and rotate fuel from front to rear & rear to front about every 50 miles and at 200 miles i fill her up again, ( about 13-17 mpg) at times it will spills fuel out to cap after driving on the highway for a while not all the times but it has, so I have replaced both gas caps. today I get ready to leave and she turn over but wont start, relays are good, fuses, accident fuel shut off is not activated and has power. I have spark, spraying carb cleaner in the throttle body she will run. i can see the fuel pump going out but on both tanks. i replaced the fuel filter and switch tanks while the engine is running with carb cleaner. looking at removing the bed instead of dropping the tanks if it is both pumps that need to be replace. so is it possible that both fuel pumps go bad at the same time?
thank you for any assistance
latest update so i seen this clip on youtube where the same issues so i try his idea. ;place a fuel pressure gauge on the fuel rail. remove fuel sector switch and run direct power from one wire to the pos of the battery and i had 37 PSI in the front tank. applied the same to the rear tank wire and i had 40 PSI. so he said it was the fuel pressure regulator that was bad.. after 3 returns to geek auto amazon and rock auto i finally got the correct one replaced it and still nothing. not like his which started easy and ran find. but so there is spark, relay is good, fuse good, auto shut down has power, good fuel pressure so i am out of ideas, . my mind is thinking computer. but dont want to think like that

 

Your supposed to have 45 to 60 psi to run this engine properly. That said, I would think it would run with the lower pressure, but not well. I pulled up on the job one day and when I got back in to start, it wouldn't. That day it was the tank switch. I put a new one in and started right up. You could look at that. Also, your truck should not be "spilling fuel" after driving. Sounds like you may have a problem with the return lines not functioning properly, filling up one tank. i don't know much about that, you need to look it up.

 

thank you for the idea of the fuel switch. I did replace it about 2 months ago going to look for the old one. I only replaced it cause it was faded. But it's worth a try. On the spilling fuel its not all the time but it's both tanks mostly after driving the turnpike and I stop I could see the wetness by the fuel caps

 

Starting in 1995 and including year 1996, the 4.9 engine should have 30-45 psi of fuel pressure.Your fuel pressure is at specs having 37&40 psi. Your regulator is fine. It is bad only if fuel leaks out of its vacuum nipple. Since you already replaced it, save the old one, it's probably not bad.The regulator actually keeps the pressure from going too high.

Do you have 30-45 psi of fuel pressure to the rail without having to hot wire your fuel pumps? If not, find out why.

 

so I check the relays that are ok but I'm only getting power to 1 leg and yesterday I had power on 2 so I lost power somewhere. Cause it starts at the relay thank you