i am having problems deciding if I have fuel flow or not. My question is, does the PCM actually stop the flow of fuel at any time. I know it regulates how much flow is presented to each cylinder. Gas flow was ok when I decided to do some turnup by replacing a lot of things, everything was working when I started. Now I can't seem to get fuel to the fuel injectors, there is no gas pressure when connected to the fuel rail port. Right now, I'm in the process of replacing vacuum hoses. The only question is will the PCM shut down fuel flow entirely if certain requirements are not met? I have not checked out things that would stop flow but those things were working before, i.e. fuel regulator, fuel filter, fuel injectors. Maybe my gas pressure guage is not working, i.e. schrader valve port not opening up when tester is attached. I will look further to determine that by just pressing down carefully on the needle at the schrader port and see if fuel is present. I have a 1999 F150 5.4L Triton extended cab, bought new.

 

Ignition On only causes the fuel pump to run about 3 seconds then shuts off.
When you begin to crank, the pump is turned On again and stays on while the motor is turning/running.
.
In the circuit there is a PCM timer (3 second run) as key On caused by powering up the a PCM.
At cranking, the Crank sensor signals the PCM to re-operates the fuel pump Relay.
The pump Relay applies separate fused power to the pump through the relay contacts.
Inline with the pump is a Crash sensor behind the passenger side Kick panel.
Read this again until you get the sequence of operation.
.
If you don't see any pressure begin to build at several Key on cycles, there is a problem somewhere in the system as explained above.

 

Seems like I screwed up, after fixing some things, I failed to plug the connector to the DPFE sensor and the truck starts fast but immediately stops. OBDii says P1401 and I immediately new i forgot to plug the connector in. I plugged it and and started the engine. It did the same started quickly but died immediately same as before. I did I damage something.

 

No, just an incidental thing.
That system is tested two times after startup to be sure the system works. Any part unplugged will fail the testing and set a code.
The reason is, in freezing temps there may be frozen moisture in the lines that would make the system test fail until the engine bay heated up enough.
After that the system does not work again until the road speed is over 45 mph and at light throttle in third or OD gear during the drive cycle.

 

I still have the problem: starts fast but will not idle. If I give it the gas as soon as it starts, it does rev up but makes some pop sound but not like a mis-fire.

 

You have Ignition ok.
Now it's time to test fuel pressure with a gauge at the test port looking for about 35 psi +/- 5 or so and holding.
No guessing, no sort cuts.

 

thanks all, problem turned out to be a bad throttle body mount gasket (kinda old and out of shape). I also cleaned the IAC (idle air control) which may have contributed...