Audi A4 2001 Owner's Manual page 20

Engine and gearbox
Injection pump VP 44 S3.5
Distributor bushing
Distributor shaft
Supply piston
Thermal shoulder
The high pressure section of the injection
pump has been redesigned with regard to
pressure levels and quicker solenoid valve
actuation.
The injection pressure at part throttle has
been increased by the following measures:
– increased cam stroke from 3.5 to 4.0 mm
– more stable support structure for high
pressure section on pump body
– conversion from 3 pistons with a diameter
of 6.0 mm, to 2 pistons with a diameter of
7.0 mm.
By reducing the number of high-pressure pis-
tons from 3 to 2, it was possible to reduce
high-pressure leakage via the sealing sur-
faces.
20
Forced flush feed
In order to initiate pre-injection for cold and
warm engines, the solenoid valve dynamics
have been significantly increased.
The associated increased heat generation in
the solenoid valve, is compensated by
improved fuel flow and optimal filling of the
high pressure section is achieved.
Noise levels have been significantly improved
by the pre-injection for cold and warm opera-
tion and the use of dual-spring nozzle hold-
ers.
Previously, pre-injection via the solenoid
valve was only realised during the engine
warm-up phase.
Forced flush
return
Solenoid valve
SSP255_040