Hey all,

So my 2004 F150 FX4 5.4l has been having an issue with the fuel system.
They checked the fuel system to see why the truck is dying and they said that the truck has full fuel pressure when it dies, and actually spikes in fuel pressure before it dies. So they are saying it is something electrical and refereed me to a computer system shop. I told them about the notorious FPDM issue and how most people have to replace them due to corrosion. They are saying they don't believe it would be that as the fuel pump and fuel system all still works when the truck dies. My question to you is?

1) What does the FPDM specifically do?
2) Could it still be the FPDM even though they are saying the fuel system is still working correctly when it dies?


Any advice would be great.

 

The Fuel Pump Driver module's name pretty much explains what it does. Kinda like a relay I recon. They are $65 at rock auto. They fail frequently in rust belt states.
You would loose fuel pressure if its the Fuel Pump Driver module.. You have a different problem.. Getting any check engine light?

 

are our fuel pumps a constant volume type pump? if so, the only reason for a spike in pressure would be a blockage...right? as if all injectors are cutting off restricting flow, causing rail pressure to rise. this is all in theory, but makes sense in my head.

 

Jethat,

I figured that what it did but was wondering direct technical behind it.. No i am not getting any check engine lights. Also great find on the FPDM.. What a price.. The cheapest i have found was $99 on ebay!!

Jethat and Stu486,

He said it is spiking in pressure right before cause when it dies the injectors cutt off of course(like Stu said), but the pump has the 1 or 2 sec delay so thats why there is a spike.. I dont think the spike is really important just thought i would add it in..

 

I was also told by a few other member on F150forum.com that this is common of the FPDM dying because the fuel system looks like its working when it dies, but actually the FPDM is bad... Any suggestions?

 

so i just read a little on fuel systems...i'll just throw some things out there that catch my eye for someone to pick up and maybe it can help.

the fuel rail pressure switch-could it be sending a false signal? seems its just an analog transistor, and could fail.

can you see what signal the fpdm is relaying to the pcm? could it be saying its doing the work it should, but in turn is not sending the pump a proper signal?

also...Culprit, did they hook an actual gauge to the Fuel rail or just go with what the pcm said it was?

 

http://www.motor.com/magazine/pdfs/072007_08.pdf

not a bad read.

 

No, it's not a constant volume/return system like the 03's and earlier were. The FPDM regulates the pump.

 

yeah just read up on it...fpdm is like a variable frequency drive for the fuel pump. fancy stuff.

 

Stu486,

I will read up on this for sure.. I also just bought a new FPDM anyways on Rockauto.com to try out and if not then ill have an extra at least for when it does go out. For now i will just drive my extra vehicle.

 

So tried the FPDM and it seemed to work great for about a 1/2 hour which got my hopes up because the truck would die usually in less then 2 min. Well then took it around the block and the last light before i got home it stalled out again!! Taking it to ford tomorrow.

 

So the final result was the PCM.. I told them to re-flash it the other day and they would not do it, but after 4 days and only charging $90 for diagnostics i think they just decided to try it and it worked!!!