Question for you guys.....I noticed my 1999 5.4L F-150 it's taking just a little bit more time to fire up. The truck is running good with no "Check Engine Light" on. Ussually it's doing it on the early morning at the very first crank of the day then the rest of the day it turn over and fire up like usual.

My first tought was that maybe the fuel pump or regulator were going away and I replace the fuel pump since the truck is already 130K miles and it deserve it. Fuel filter was also replaced. The problem still there and I notice that the fuel pump is not activating with the ignition switch in the on position. So there is no fuel pressure at the switch on engine off position.

Other than that, as soon as the engine fire for the first time in the morning, it keep starting and running good for the rest of the day with no missfire or hesitation.


Any ideas Welcome

 

Did you replace the fuel pump relay when you put the new pump in? Have you put a fuel pressure gage on to see if the system is leaking down over time?

 

Remember, the fuel pump is only run for about two seconds when the ignition switch is first switched to RUN in order to pressurize the rail. After that, it doesn't get turned back on until the PCM detects an accelerating crank signal which indicates the engine is firing.

Listen for that two-second burst.

Steve

 

I checked the fuel pressure with the engine running and the pressure is OK. That's when I noticed that the pump is not primming the rail. There is supposed to be an increase of pressure just with the ignition key on "key on engine off position". Then when the PCM detect that the engine is firing the pressure should remain constant. This is not my case. With the ignition key on the "key on engine off position" the fuel pump never operate. I don't hear any noise from the pump and don't see any build up in pressure on the gauge.


Then when I keep cranking the engine the fuel pump operate, the pressure finally buid up and the engine fire up. This is only happening in the first cranking attempt of the day. From then on the engine fire up fine because the rail remains more or less pressurized for the rest of the day. This condition only show up when the engine is stopped for maybe 8 to 10 hours during the night.

Any ideas welcome