Those readings are fine to me.
unless it's some really odd esoteric fuel line/fuel pressure/fuel tank
situation..
I wouldn't give fuel pressure or delivery much more thought at this stage.

I would think more about the electronic side of fuel control.......odd
intermittentancy there.

even air flow meter ..
since that is 'the one spot' where something electronic interfaces with
something mechanical..
always a weak area. ( something that is completely transcended by the
next device up in terms of EFI developement..the Air Mass Meter ..with
no moving or mechanical parts at all  - just need to have a whole subaru
engine attached to one to advance to air mass meter though ...another
subject entirelyof course. )

And I have had waterboxer intermittent 'uneven' fuel delivery be caused
by an old iffy AFMfor sure. I'd consider that component for sure.
And resist the temptation to think it's just One Thing ..
it could easily be 8 minor and/or  'half-things'.

On 7/24/2013 9:03 AM, Alistair Bell wrote:
> Well, it is a USG (US Gauge) pressure gauge. You can't be doubting those readings can you?
>
> :)
>
> Yup, Bentley gives value in Bar and psi. 2.5 Bar = 36.25 psi. Leaving aside gauge error, I was just wondering if the extra 2psi would be enough to enrichen things beyond the O2 sensor's control ability.
>
> cheers
>
> ab
>
>
> On 2013-07-24, at 8:39 AM, David Beierl wrote:
>
>> At 10:47 AM 7/24/2013, Alistair Bell wrote:
>>> I got a value of  (at idle, vacuum hose on/off) 32/38 psi.
>>>
>>> Bentley says it should be "approx. 29/36psi.
>>>
>>> I'm wondering if my readings are within acceptable range or are indeed too high?
>> I wonder how accurate your pressure gauge is.  The spec I believe is 2.5 bar, and your regulator certainly appears to be regulating.  The only way to see how it's doing in transient response would be to use/make a differential gauge that uses manifold pressure instead of ambient as a reference.  If you did that it should show a basically static reading of 2.5 bar under all engine conditions.
>>
>> It's a spring-loaded diaphragm blowoff valve that vents to the tank return line.  I've never had one apart, but seems to me the spring could perhaps get weaker but not likely to get stronger, and I don't *think* there's a lot of opportunity for it to get sticky.  The usual failure is a leaky diaphragm that pours gas into the manifold through the vacuum line.
>>
>> Yrs,
>> d
>>