Pre-Injection Phase Starts - Volkswagen 1.9-Liter TDI Owner's Manual

Pump Injection System

Pre-Injection Phase Starts

The injection cam pushes the pump
piston down via the roller-type rocker arm.
This displaces some of the fuel from the
high-pressure chamber back into the fuel
supply line.
The Diesel Direct Fuel Injection Engine
Control Module J248 initiates the injection
cycle by activating the pump/injector
solenoid valve.
Roller-Type
Rocker Arm
Injection Cam
High-Pressure
Chamber
Retraction Piston
22
The solenoid valve needle is pressed into
the valve seat and closes the path from
the high-pressure chamber to the fuel
supply line.
This initiates a pressure build-up in the
high-pressure chamber.
At 2,611 psi (18,000 kPa / 180 bar), the
pressure is greater than the force of the
injector spring.
The injector needle is lifted from its seat
and the pre-injection cycle starts.
Piston Spring
Pump Piston
Solenoid
Valve Needle
Pump/Injector
Solenoid Valve
Fuel Return Line
Fuel Supply Line
Injector Spring
Injector Needle
SSP209/025