Hello, I am John, a Ford dealer technician.
I hope I can help solve your problem quickly and accurately.
The easiest way to bleed air out of the system is to take the cap off of the upper filter. Now turn on the key and wait for it to fill up to the top. Once full reinstall the cap and attempt to start. If it still won't start you got another problem.
I hope this answer has been helpful to you! If you have any further questions please feel free to ask.
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Sounds like you got a problem that requires more attention. I'm going to opt out so another expert with more experience with 6.0 engines can help. Please do not respond because it will lock me to the question and others will not be able to respond.
Thank you for using just answer.
When you took the cap off was there any fuel in the filter housing or was it empty?
Do you hear the fuel pump turn on under the truck when the key is turned on?
Was the engine light on before no start?