Been banging my head on this for 2 weeks. Have gotten some great information searching here. Running out of options and possibly my capabilities.
04 F150 5.4 3v. 102k miles. Spark plugs new around 30k not that that matters in this case.
Will run perfectly fine for several min. Either driving or at idle. At random is appears the fuel pump looses power. Truck will run down to zero fuel pressure and stall. Let set 30 seconds. Restart and repeat. After the first stall I only get about 1min and 40seconds and the issue repeats and repeats. I run and Edge programmer. Just recently was educated that I can use it to monitor fuel pressure in real time. This info has validated my theory. Upon start up fuel pressure is 70-50. Quickly settles down to about 40 when running. Will run at normal pressures 35-45 for couple min. At random it will just start dropping to zero and truck will stall. At least with the programmer I know when its coming so i can get out of traffic and pull over!
This is what I have done in the last 2 weeks:

• Dorman FPDM (about 3yrs ago). I put a new one on last weekend. No change so returned it for refund.
• Replaced fuel filter. Was dirty. Not horrible. Not plugged.
• Replaced fuel pump & canister assembly complete (Delphi). Didn't really think this was the issue but it old one sounded like a box of rocks so I wanted new before winter anyway. Old pump screen/sock was not dirty.
• Cleaned tank. It was not dirty but had a few bits of sediment in it. Cleaned it spotless prior to installing the new fuel pump.
• Removed fuel pressure sensor on the driver side rail. Appears clean. no obstructions. Pull vacuum hose off it while truck is running. Has good vacuum. Does not effect issue. Truck will loose fuel pressure weather the vac hose is on the senor or not.
• Pulled vac hose off the purge valve canister on the driver side fire wall. Seems to toggle between pulling vac and not. Either way does not effect issue. Removed it (purge valve) and you can not blow through it. From what I have read that indicates it is good.
• Gas cap. Remove gas cap while truck is hot. No release of air (no pressure build up). Running truck with gas cap off. No change in issue.
• Relay. Removed fuse box. Disassembled to access circuit board. Continuity test on soddered relay is good. Board and relay look good. No burn marks. Nothing discolored on either side of the board. Upon reassembly, blower motor for heater no longer works (im sure thats my fault).
• Plugs under driver seat area on frame. Can not get the large plug set apart. Got the smaller one apart. Looks good no corrosion. Cleaned with contact cleaner. Reconnected. Seems I really need to get the large plug apart as other have found corrosion. I will go there this afternoon.
• Fuel cut off or "inertia switch" - bypassed it by removing plug on switch. Sticking a mini fuse in plug giving the 2 wires continuity. No change. I was really stoked about this before I tested it cause it made sense that the switch was cutting off the fuel pump.
• Cleaned throttle body, mass sensor. Unrelated but needed done anyway.

Really love this truck. always have since I have owned it since 06. No real issues until now. Getting really bummed that I can get this straightened out. Electrical is not my strong suit. Looks like we are to the point I will need to stress my skill level. Really hope I dont have a PCM issue.

Any input on re-checking anything I have already checked? Any input on what else to test (probably how to test it also)?
Much apricated.

 

This afternoons progress:

• Got large plug under driver seat area on our side of frame separated. Dirty but not terrible. Cleaned out with electrical contact cleaner.. Re connected with small amount of die electric grease. No change. Ran about 2min.
• Searching for grounds. Ground right above the FPDM was pretty bad. Thought might finally be my smoking gun. Removed it. Put new ground on underside so more accessible. No dice. Ran about 2min again before stalling out..
• Inspected ground at fuse box on passenger side inside cab. Looks brand new. zero corrosion. No need to tinker with that one.
• Moving to under the hood on search for grounds. Also looking for any vacuum leak that could effect fuel pressure sensor. Pulled battery and trey to inspect the square vacuum box between battery and fender. Looking for cracks. Not finding anything. There is a check valve in the vacuum line between the battery and passengers bank of cylinders. Pulled it off. Gave it a blow. It is functioning as designed. Will only pass air one direction.

Starting to pull the drivers side fuel rail now. Feel like this is a bit pointless but I am getting an injector 6 fault code. Likely just from it running out of fuel first. Hoping I come across something while doing this. I guess it wont hurt to look at 20yr old injectors.

 

Install a meter or test light at the inertia switch so that you can see it. You'll want to see if the voltage supply to the fuel pump is dropping out or not. Once you know that, you're in a better position to diagnose.

 

Since having the inertia switch out in the open (currently bypassed with a mini fuse stuck in the plug). This should be an easy check when i get home this afternoon.

What should the voltage be for proper operation?
If it is dropping (which i believe it is). What is that an indication of?

Thankyou for your reply!

 

Battery voltage, whatever that happens to be at the time while the engine is running.

It indicates something "upstream" isn't working properly.

It is important to note that the voltage at the inertia switch will, with the engine NOT running and ignition in RUN, typically read 6-7 volts after the FP relay has de-energized. This is normal is not indicative of a problem in itself.

 

• Wow. You sure have done a lot and are persistent. Reminds me of some of the problems I've worked on that took forever to figure out. So I'd like to help.
• I'm too busy right now to give this more time so will try to get back to it later, hopefully tonight.
• In the meantime, you could try letting it run while you get underneath and start jiggling, pulling, and twisting the wires at the FPDM and the wires going to the fuel tank and the wires coming to the FPDM. Then trace the wires forward and do the same thing to see if any wire movement affects the problem.

Good luck.

 

No joke on the persistent ! I cant stand it when one of my babies is not healthy.

Agree on your suggestion with the wiring. I started on this yesterday. including unwrapping the harness back 3-4" from plugs on the frame and at the FPRM. Have not found anything yet but by god something has to show its self soon or I will be in the loonie bin.

Its also time to get out the multi meter and start testing points as projectSHO89 has recommended. Thats going to start getting me out of my comfort zone. Im not the electrical guy but if I want to fix this I will have to get with the program. I downloaded some wire diagrams while at work today. Should help me some.

I really do appreciate the incite in my time of need!

 

OKAY.projectSH089.
Had to dig out my old Fluke 77.
With truck running. Im getting .010.5 VDC consistently. Also holding 35-39ps fuel pressure. After around 2min the voltage dropped to .002 and fuel pressure followed very quickly. I shut it off just before it stalled out.
Readings were taken with the meter probs stuck in the back of the plug and the switch still bypassed with a mini fuse in the plug.

Does this indicate a problem before the switch (relay and PCM)? If this and I have a bad feeling with this. How to test between PCM and relay?
Or down stream (FPDM, pump, pressure sensor)?

Thank you for your time and effort on this!

 

Looks like the measurements were not made correctly so the results are not useful.

You should have the black meter lead connected to ground and probe with the red lead (unless instructed otherwise).

 

Sorry. This is me learning about DC voltage and learning to use a multi meter at 45yrs old. A bit shameful. Ill get over it..

Correction. With black meter wire at ground right next to fuse box. Red meter wire on either the orange wire or the green/yellow strip wire. Results are the same.
12.5v with key on not running. Quickly goes to 14.2v and maintains with truck running.
Decided to go for a drive as I am sick and tired of stalling out in the driveway at idle.
Ran about 8min at 60mp. I was varying the throttle. When it cut out. It was instantly. Fuel pressure went from 39 to 0 nearly instantly. Unlike at idle where it will count down over maybe 10 seconds. I suppose that's the difference of the engine being under a load.

Anyhow the voltage at the inertia switched never changed. When pressure dropped out my eyes instantly went to the meter. Never went below 14v until engine stalled.
After the first stall I switched my red meter lead from orange wire to green/yellow strip wire. Got the same result on the way back home.

I assume from here I need to do similar voltage reading back at the FPDM?

*Note: Friend of mine stopped by while I was at work yesterday. He put a gauge on the fuel line right after the filter. Stated that the manual gauge was reading the same as the digital gauge on the programmer for fuel pressure.

 

Here's a couple of more things you could try.

1. Disconnect the FPDM wire connector.. Then check the ohms between that the battery negative terminal and the black with yellow stripe wire's socket. There should be 0 or close to 0 ohms resistance.
2. From Ford 2004 F150 Workshop Manual:

• Bypass the FPDM to supply power directly to the fuel pump. Connect a jumper wire between the black with yellow stripe wire’s socket and the brown with white stripe wire’s socket (terminals 2 and 3). Connect a second jumper between the white wire’s socket and the pink with black stripe wire’s socket (terminals 4 and 5). Crank the engine to see whether it now runs right. If it does, replace the FPDM. For the best reliability get it from Ford as after-market ones frequently fail. If it still has the problem, further testing will be needed before replacing the fuel pump.

 

Ground to blk/yellow stripe wire on plug is 00.1 ohms.
Ground to corresponding pin on the fpdm is 00.0 ohms

I have jumped out the FPDM before as your directions indicate. Truck will start just that same as it does running on the module.
What i have not done is let it run for a period of time like that. Is it ok to let it run with the fuel pressure pegged at 75psi for like 10min?? I dont want to create any more problems then i already have.
If its not going to be an issue I will certainly run it jumped.

I currently have the tank lowered a bit. Just got the fuel pump plug off. Trying to figure out how to back prob the wires without damaging the weather tight seal. Effort to watch the voltage while the truck is running.
Any suggestions on a voltage test at the fuel pump?

Thanks.

 

Put the jumpers in place again. For a long duration this time.
Went for 5min (timed it) drive. Did not stall.
Checking some operations while driving (fuel pressure pegged entire time at 75.5psi).
Blower for HVAC does not run in any position 1-4 figured this is my own doing since I took fuse box out last weekend.
Also found cruise control and turn signals not functioning. I think this is a new development?
Found fuse blown for turn signals. Strange
Cruise control still not functional. The little icon does not come on the dash when you push the on button. Have not located a fuse yet.
I should add this truck has lived a sheltered life. Stored the first 5 winters i owned it. Its not very rusty. Frame and undercarriage is a bit corroded. Body just barely starting to rust. all the wiring is in really good condition.

Back to the main issue. The fuel. Replace turn signal fuse and went for additional 5min drive. Did not stall
Turn signals still function when i returned.
I find the odds extreame that the Dorman FPDM I have been running on for 3yrs randomly fails AND the brand new one (Still Dorman) is faulty with the exact same symptoms? Seriously? I guess anything is possible.
I have no problem ordering the OEM module but am not convinced this is the smoking gun.
Will do anther test drive in the morning although i hate stressing the system at 75psi. I just need a bit more convincing.

And those little jumpers I made will never leave that truck. EVER.

 

Good to hear that it sounds like you found the problem. Like you said though, it's best to make sure before shelling out the $$$ for a Motorcraft FPDM. One last thing you could do is to put the new Dorman one back in to verify that the problem returns.

As for the other problems, it might help to start a separate thread for them, after the fuel problem is definitely fixed.

 

Keep in mind that the PCM can turn off the fuel pump via the FPC control line to the FPDM, either intentionally or due to a fault in that control line.

It's necessary to monitor the FPM and FPC PIDs to see if the PCM is doing something that is causing the issue.