[Vwdiesel] pump internal pressure

gary gbangs at cfl.rr.com
Sat Feb 26 18:20:51 EST 2005

What I remember,

There is a device next to the fuel inlet that regulated the fuel
pressure along with the orifice. The center section can be driven in
with a drift ever-so-slightly increase pressure. But if you go too far,
you can drive the center piece out of its bore... Big hole!


On Sat, 2005-02-26 at 13:00 -0500, SLATERSFB at aol.com wrote:
> I kinda remember reading a while back in a thread that inj pump internal 
> pressure is determined by the orifice in the outlet banjo.  If I recall 
> correctly 
> also the internal pressure drops as the pump gets older detrimentally 
> effecting pump timing over the whole timing advance curve.  How about making 
> a special 
> banjo with a fine thread set screw to adjust the orifice size in order to 
> compensate somewhat for pump wear?  Possibly one could get better resolution 
> of 
> adjustment running the threads at an angle.  Does any of this make sense to 
> anyone?  Anyway, I'd love the refresher course on the subject, as it is a 
> vague 
> memory at this point.
> Andrew
> _______________________________________________
> Funny you should mention this. I have old pump here which I took apart two 
> weeks ago in the evening just for curiosity. I could be wrong, but seems like 
> internal pressure is first regulated by a spring loaded regulator very near the 
> inlet banjo. Sort of like an oil pressure regulator in principle. But constant 
> pressure would not advance timing with RPM, so I guess that is the idea of 
> the pin hole in outlet banjo? This is the first pump I evr disassembled 
> completely so I am sort of feeling my way along here, but it seems like the vane pump 
> is way huge compared to the maximum demand at full throttle. Like overkill. My 
> guess is that the spring in regulator, if some way to regulate this, would be 
> the way to compensate for wear. Do these vanes ever wear out? The only wear I 
> found in this pump was the four small shafts, that support the rollers that 
> the cam plate rides on, were sort of pitted. Like roller bearings when they 
> begin to make noise. 
> Still & all this is one beautifull piece of machinery inside. My mind boggles 
> when I think of what goes on in there at such precision & for so many 
> millions of revolutions without failure.
> Bob in NY 
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