[Vwdiesel] Injection Pump Bosch VE ( understanding the functions. )

[H.Hagar]

How did all this start for me ?  --- the day I got my first Rabbit.
1980 1.5 L NA .  I called a major dealership service department
(Capilano VW) and asked a simple question.

H : What exactly does the cold start knob do ?.
C : It injects extra fuel for starting.
H : How does it do that ?
C : There is an extra injector in the cylinderhead.
H : Thank you very very very much.

Right there I knew the guy did not have a clue.So since I could
find no one to explain. I got hold of an old pump. Now about 7 years
later I know a lot more about the VE pumps.

A short while ago one of you called the Vane pump a "Liftpump".
That got me to think maybe I should explain exactly what it does.

Yes it will lift fuel from tank to pump , but it has fare more important
functions.
The most important function is that of  "charge pump" for the injection
distributor.       The high pressure piston moves back and forth and 
rotates at the same time. At 5000 RPM engine the piston rotates at
2500 RPM.  With no charge pressure the fuel would not be able to
fill cylinder considering how small the drillings are and the short time they
match up.  The vane pump boost the inlet pressure to more than 100 psi.
Another function of the vane pump is that of dynamic timing. As RPM increases
so does advance of injection.
Hope this help some of you out there - and by all means keep a sharp eye out
for mistakes. And let us know.

Ashamed that you may be wrong ?  don't be ---you may just shake out some
of the "REAL" wizards here ---and we will all gain.

Hagar.

PS: Bosch did a lot of work to reduce cavitation  problems.