awilson40

How stable should the fuel pressure be??
Mine will oscillate about 1 - 2 psi at Idle
in time with the injector pulses. Rev it and the pressure smooths
out. I dont have any excessive noise like the damper is bad.
I was just wondering?
Thanks

Jeremy Himsel

Mine does the same thing but it doesn't affect drivability. I think it's a dampner issue. I use the rail mounted gauge.

NZ951

Railed mounted gauge here, is does not dither at all. Could be a bad gauge, lol.

Porsche-O-Phile

Yea, or bad dampener like you said. Check for vaccum leaks going to the dampener first. . .

awilson40

No Vac leaks and the damper holds vacuum fine.
I have been trying to smooth out the idle and I notice the
oscillilation. Also notice a slight dip in pressure when the idle would
get rough. FPR is good, Injectors professionally cleaned so I wonder
if it could be the damper or my fuel pump.

Asarus

Hi awilson40;

I have the same thing here. My fuel pressure is set to 45/46 psi and when on idle it oscillates maybe 2-3 psi. I have the Lindsey AFPR and the Lindsey (VDO) fuel gauge mounted on the fuel rail. I was also wondering about my dampener or fuel pump as i have so AFR issues (impossible to set up as it should) ?

Porsche-O-Phile

Possibly the fuel filter too?

Asarus

Probably not in my case. Mine was changed 5.000 miles ago...

awilson40

My filter is about a year old...It may be normal, with all 4 injectors firing at once it could cause pressure to vary even with a good damper. To really smooth
it out I would think it would need an accumulator like the old CIS cars.

Tom M'Guinn

Mine does the same... vibrates 3 or 4 psi at idle at least...

awilson40

cool, thanks guys

Asarus

Here is a small video of my fuel pressure gauge when motor cold on idle. The fuel pressure is set to 45/46 psi. There you can see it oscillates between 40 and 42 psi...

http://www.asarus.com/divers/fuel_pressure.mpg (450 kb video)

TT

Have you checked it with the FPR vacuum disconnected and plugged? Wondering if it still oscillates then.

awilson40

Hi TT,
Merry Christmas
IIRC, yes, it's the same. vac on or off
and it doesnt vary quite as much as the vid.
Seb, Thanks for the video.

Darius Juca

mine osclates at idle too but only 1 or 2 psi...when gassin it off idle however it does dip and then stabilize back up....is that normal?