[Vwdiesel] '00 Golf IP pump seal problem

[pmdolan at sasktel.net]

I guess the whole point is that most systems do NOT deal at all well 
with dissolved air that has been released in the supply side.  You will 
note than on VE pump VWs, there is a "needle lift sensor" that provides 
the actual timing reference - since you can NOT count on position of 
rotating masses to do so with enough accuracy to meet current standards 
of emissions, economy and power.  This, BTW is why CRDs work so well 
(NO timing error from compression as system pressure is sufficiently 
high to deliver all fuel to injectors with air fully in solution - i.e. 
above miscibility pressure. 

On Wed, 7 Sep 2011 11:14:04 -0700, Tad  wrote:

       Fascinating that there is so much detail behind a seemingly 
arcane and (per the Cat example) sometimes disregarded bit of 
engineering. 

Of course I exaggerate with the 50/50 comment, and an increase in 
bubbles can indicate a leak, but in my experience you'll never get rid 
of all the air and the system is capable of dealing with quite a lot of 
air before you see any issues.  I could be wrong but it seems like it 
can take days before the residual air is purged from the system after a 
filter change and you get down to the "normal" small amount of trapped 
air. 

But then again I'm still using the stock clamps, 10 years and numerous 
filter changes down the road. :)

On Wed, Sep 7, 2011 at 5:47 AM,
  wrote:

       As Tad notes later, it is a matter of degrees, not absolutes.   
Unfortunately, this is a judgement call, but the fact is that suction 
or pressure, doesn't matter which, just pumping fuel through a fitting 
will released dissolved air.  It takes several thousand psi to put it 
back in solution (thus, why ALL non-common rail engines have timing 
errors while the air in injectors and lines compresses - and some 
engines - CAT HEUI in PSD installation - are so bad they will shift 
timing to way before TDC or even miss at idle on #8 - the so-called 
"cackle and knock" syndrome which is due strictly to incompetent 
management of the dissolved air released before the injector)

On Tue, 6 Sep 2011 13:00:00 -0400 (EDT), lbaird119 at aol.com wrote:

  Except that the bubbles are in the suction line, prior to entering 
the pump.  Sure,
a vacuum will do (is essentially) the same thing as you described, 
there hopefully,
isn't enough vacuum in the supply line or else the pump won't pump well 
and there's
probably a restriction in the line.   In my experience, those bubbles 
come from leaking fittings/connections.  On the
Rabbits, it's the hard line to rubber line, behind the fuel filter or 
the line itself, at the
fuel tank.  On both Passats, it's been the thermo control on the fuel 
filter or the crimp
fittings on the clear line itself.  Leaks between the crimp and the 
crimps and the hose.      Loren

-----Original Message-----
From: pmdolan

  To: vwdiesel ; Stephen Sherman
Sent: Tue, Sep 6, 2011 4:41 am

  Subject: Re: [Vwdiesel] '00 Golf IP pump seal problem

  It is not likely that you have any air leaks.  ALL liquids stored in

  atmosphere have a tremendous amount of air dissolved within.  When you
put fuel through pumps, fittings, etc. where the flow must cross or be
forced around very sharp edges, the resulting low pressure releases
some of that dissolved air, and that is what you will ALWAYS see in the
clear lines of VW diesels.  Think about pictures of submsarines or
even props on regular surface vessels - they always have a trail of
bubbles coming from them. That is dissolved air being released from air
(and why it is so difficult to make a submarine quite - when those

  bubbles implode them make a very loud noise that is easily detected by
sonar - and that same implosion is so violent it blows little bits of
metal off of propellors and impeller - called cavitation wear. I could
write a book about which diesel engine designs don't work as intended
because they don't deal with dissolved air properly/  And, yes, in
case you are wondering, this is one of the things I do for a living -
make equipment to remove dissolved air from oil). 
On Mon, 5 Sep 2011 21:22:56 -0600, Stephen Sherman  wrote:
Well a bit more as things unfolded... 

Car drove well for a week, then one day I noticed a strong fuel smell. 
Looked under the hood, and the IP was leaking from the seal below the 
QA. Pretty obviously that gasket from the wet area and dirt.  Order the 
gasket kit and special tool, and replaced that and the top cover 
gasket. Got the QA adjustment back into the working range (good idle 
now), and things seem OK. At least no signs of new fuel leaks around 
the IP.  Definitely would suggest multiple alignment marks if you do 
this, as I needed to rely on a second set to get the QA in spec. (The 
epoxy chipped off as I took it apart, so wasn't able to use those marks)

Still have some air leak, as I can occasionally see a stream of bubbles 
in the fuel clear line. Hoping its not one of the IP gaskets I replace. 
Will replace the injectors furl return line as it is getting pretty 
old. And take a closer look at the main return and fuel lines. But at 
this point, the only symptom is the air bubbles in the fuel line. No 
obvious leaks anywhere. _______________________________________________

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