Aussie VM (MK7) high idle rail pressure

[351fairlane71]

Hi guys,
I'm usually ok at nutting out problems with this thing, but...
I have a 600k km old and well looked after 2008 2.4TDci, and have had to replace injectors, SCV/PRV, EGR etc for all the usual reasons (idle/FRP issues) over the years, but I'm a bit screwed up by this one.
It's been giving the usual surging idle, fluctuating rail pressures and noisy combustion in combination with the usual EGR fault codes issues (I use FORScan) so I have replaced the EGR (updated/water cooled) plus the SCV/PRV and also pressure sensor. Cleaned out the intake, cleaned the MAP and MAF and fitted a new fuel filter.
It now starts easily, but still has the combustion rattle and surging cold idle but the idle stabilises at operating temp. The fuel pressure at idle is very stable, but high at approx 10,000psi (where it should usually be 3500psi).
The odd thing is, the higher the engine revs, either driving or free revving, the closer together the actual vs desired pressured get. Once I hit around 2,500rpm, both actual and desired are around 20,000 psi... which seems about perfect to me.
I know we've all seen rail pressures bouncing all over the shop and massively high no matter the revs, but has anyone seen something this specific... high at idle but good at revs???
Cheers guys... Craig
PS... I've had the new SCV/PRV/Sensor for a couple years (I believe in being prepared) but can't recall where I bought them... may have been either Fleabay or TPUK.

[knobby1]

Have you had the codes read..?? Have you done a set of learns recently..?? Are your new valves genuine Ford/Denso items.?? If not you've probably wasted your money.

High fuel pressure is usually SCV related.

Lord Knobrot

[351fairlane71]

Have you had the codes read..?? Have you done a set of learns recently..?? Are your new valves genuine Ford/Denso items.?? If not you've probably wasted your money.

High fuel pressure is usually SCV related.

Lord Knobrot

Hi Knobby, thanks for the reply mate.
The only current fault code is the PTO switch open which is unrelated. The learns have aborted due to the rail pressure difference at idle. Like I said, I'm not sure if the SCV was genuine but I'm starting to think it wasn't... perhaps I just get a new one from the dealer and be done with it.

[knobby1]

Have you had the codes read..?? Have you done a set of learns recently..?? Are your new valves genuine Ford/Denso items.?? If not you've probably wasted your money.

High fuel pressure is usually SCV related.

Lord Knobrot

Hi Knobby, thanks for the reply mate.
The only current fault code is the PTO switch open which is unrelated. The learns have aborted due to the rail pressure difference at idle. Like I said, I'm not sure if the SCV was genuine but I'm starting to think it wasn't... perhaps I just get a new one from the dealer and be done with it.

May be your best option...they're bloody spendy though..!

I was able to pull my SCV apart and polish the little piston and it's bore, they get scored and sometimes stick which causes hysteresis and the result is usually a hunting idle. If they stick solid they can cause either too much fuel pressure or too little.....they must be at the correct spot at some stage I guess...just like a clock that doesn't work....it's right twice a day.!!

Lord Knobrot

[351fairlane71]

Holy COW Knobby, you're right about the price from Ford (bend over and take it up the ...)

Anyway, it's ordered. One question though... the SCV mounting flange looks symmetrical, can it be fitted either way? It looks like it can go in with the plug at the top or at the bottom.

Thanks for your time.

Craig

[knobby1]

Holy COW Knobby, you're right about the price from Ford (bend over and take it up the ...)

Anyway, it's ordered. One question though... the SCV mounting flange looks symmetrical, can it be fitted either way? It looks like it can go in with the plug at the top or at the bottom.

Thanks for your time.

Craig

It is symmetrical and shouldn't matter which way it goes...l just refit them the way they come out....there's two O-rings, be sure they both come off...and go back on.

LordKnobrot

[351fairlane71]

Ahhh cool... thanks for the help mate.

I'll post the results after the weekend.

Cheers