I have a 1990 f150 lariat 5.8, when the truck warms up and I'm driving for a bit it acts like its out of gas, so I stop, get gas and resume then once it warms up again the problem proceeds. I have changed the fuel filter and it didn't change a thing. Any help will be greatly appreciated

 

Maybe the vent is plugged up.. Have you noticed a sucking sound when you pull off the cap?

 

Nope no sucking sound

 

Put a fuel pressure gauge on it, one with a long hose so you can tie it off to a wiper arm and watch as you drive, sounds like your fuel pump is going out.




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This is what I was thinking too, but then when he mentioned it would run normally after pulling the gas cap off. I leaned towards the vent system.

The OP could isolate by running with the cap off, this would eliminate the vent system. If it stayed running then that would point to the vent and if it stopped he would want to lean towards the pump/supply system.

 

https://www.f150forum.com/f10/how-re...es-obdi-10907/
And pull engine vacuum.