[Vwdiesel] pump internal pressure
SLATERSFB at aol.com
SLATERSFB at aol.com
Sat Feb 26 13:00:56 EST 2005
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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