Boston 04 F150

When starting my 04 4.6L with engine cold, it needs to crank longer and longer… cranks for 5 seconds then starts.

Issue not as bad with warm engine. This has been happening for past 5-6 weeks. No check engine light, no codes in PCM.

Relevant info:

New battery 6 months ago
Replaced fuel pump driver module 3 years ago, I did a visual inspection looks to be in good shape.
Replaced fuel filter with OEM couple weeks ago (after this issue had started)
MAF readings seem to be within spec
Fuel rail pressure key on engine off, and truck running both within spec.
Short term fuel trims look good, bounce negative to positive hover around 0.

To my question. My fuel tank pressure readings are always -0.01 or -0.02psi that’s with the engine running, key on engine off, stays pretty much the same.

What is fuel tank pressure supposed to be?

Is there a way to test or activate EVAP purge valve? My scanner is decent but doesn’t let me send commands to EVAP or anything. Thank you

getterdun

I'd try this next, if you haven't already:

GoneBallistic

would this same test on the fuel pump apply to a 5.4? I just put a new engine in my 5.4 in about October. it's been starting and running fine, but last few days it's starting harder. I can get it to start but it stumbles a bit upon start, and sometimes fails to start. and when I try again takes a few seconds, finally starts then smoothes right out.

I am guessing either fuel pump or the FPDM. but I have no idea. Could also be cause my tensioners have failed (It's a crappy powertrain products motor built by ATK with dorman tensioners that have already failed with under 5K miles)

Boston 04 F150

I looked for schrader valve on rail and don’t see one… does the 2004 4.6 not have one? That was a helpful video, thanks

redfishtd

Ford stopped putting shrader valves on engines a long time ago . My experience on hard starting was tied to fuel pressure and how fast it disappeared after shutting down. I had changed out fpdm and then injectors at 130 k so 125 miles later at 255k I figured the fuel pump check valve was failing -wrong ,it turned out one injector was shooting a stream with no power another was dripping . I had wasted money changing fuel pump assembly , Put all new injectors in from dura last guaranteed .
But unfortunately the massive fuel going into the intake broke lose all that pcv oil scum in intake causing cat efficiency problem on that side leaking . Still running good at 270k miles .
I am happy it did not hydro lock my engine and bend the rods or worse .Don't know if I'm going to change cat or rod it out .

Jimboy

Does your 2004 utilize a Fuel Pressure Regulator with a return line to the tank or a Fuel Pressure sensor? Auto supply houses list both for 2004.


Fuel Pressure Regulator
The fuel return line is a hose that returns excess fuel from the engine to the fuel tank where a fuel pressure regulator is used. Fuel injection systems may or may not have return lines. RockAuto.com $28 for the regulator.

Fuel Pressure sensor
A returnless-type fuel system is one that is designed to use the powertrain control module (PCM) to regulate fuel delivery. A fuel pressure sensor mounted to the supply rail of the fuel injectors allows the powertrain control module to keep an eye on the fuel pressure.

Sounds like a failing fuel pressure regulator which is allowing pressure to bleed off over time.

getterdun

Oops. Posted before finished...in progress...

getterdun

I think so too. Try turning the key to the Run position and holding there for a few seconds before turning to Start to allow fuel pressure to build up.

Boston 04 F150

Tried this above few times, no change. I’ve noticed recently that with engine hot and not sitting to long, it has to crank less (still more than normal just not as bad)



I did a search for “fuel pressure” in manual, there is nothing about regulator only sensor

Some details about sensors..How do I check that sensor is bad?

Jimboy

Take a picture of you fuel rail showing Fuel Pressure Regulator OR Fuel Pressure Sensor and post this photo. We need to know what system you truck is equipped with.