tell me about fuel pressure...

[dtpoirot]

Howdy all,

I have a stumble at idle and mileage is not what one would hope for. ...but I do have a heavy foot when I am enjoying the LS.

The Service Manager at the dealership told me the LS had a single high pressure fuel line and not the return loop system that I have seen before.

He also said that the rich condition could be caused by either a pressure sensor failure or a fuel pressure regulator failure.

What does the collected tribal knowledge have to say on the subject?

Should I troubleshoot this or take it in?

Thanks!
- dan

 

[Quik LS]

the LS uses a returnless style fuel system - meaning the pressure is maintained by driving the fuel pump at a duty-cycle to achieve the desired pressure - as read form the pressure regulator mounted on the fuelrail.

It's a fairly standard Ford setup - looking for 40psi at the injector nozzle - so at idle you should see roughly 30psi at the rail (since you will have -10psi in vacuum in the intake).

Were the LS is unique (from other Fords) is that it does not use a separate FPDM (fuel pump driver module) and that function is built into the REM (Rear Electronics Module). It's the only Ford I know of that does it that way.

First thing I would do is check vacuum at idle - make sure you are pulling 18hg-22hg - if you are not - then you have a vacuum leak, IAC vavle issue, ...etc

 

[joegr]

I suspect that you are looking in the wrong place. The fuel pressure sensors on these cars don't seem to go bad. Marginal COP (Coil On Plug) failures are very common, and your symptoms suggest exactly that.

 

[FASTLLS]

I would agree.. Did you have any CEL?

 

[dtpoirot]

This is my second LS...

The first was a spectacular V8 '01 that was crushed when a tractor trailer turned right from the left hand lane. I suffered with a '10 Camry for about six months until my Lincoln dealer found me a sweet '03 with 19K miles!

The first one lost every single COP. So I know the signs. Little did I know at the time that valve cover gaskets could be the problem...

I saw a CEL but it read as rich at the O2? ...or something like that.

If the FPS doesn't go bad and there isn't an FDPM to even look for, I may have to play with the COPs after all...

Thanks for all the ideas!
- dan

P.S. Any point in having the ECU and associated computers reflashed?

 

[joegr]

This is my second LS...

The first was a spectacular V8 '01 that was crushed when a tractor trailer turned right from the left hand lane. I suffered with a '10 Camry for about six months until my Lincoln dealer found me a sweet '03 with 19K miles!

The first one lost every single COP. So I know the signs. Little did I know at the time that valve cover gaskets could be the problem...

I saw a CEL but it read as rich at the O2? ...or something like that.

If the FPS doesn't go bad and there isn't an FDPM to even look for, I may have to play with the COPs after all...

Thanks for all the ideas!
- dan

P.S. Any point in having the ECU and associated computers reflashed?

You could also try cleaning the MAF.