Hi I have a 2001 5.4 f 150. I irked it with the low fuel light on then about an hour later I went to start it. But it wouldn't start. I thought I just ran out of fuel but I put 5 gallons in an still won't start so I changed fuel pump and fuel filter and fuel pump relay. I Get Fuel pressure but of you hold the *** down it only last for 1 sec. Help me please

 

can you hear the pump buzzing when the key is turned to the on position?

 

For like a second

 

Hook up a fuel pressure gauge - what does the pressure build to, and what happens when you turn the key off?