VW Fuel Systems & Injection Technology 2

Question 1

In a VW direct injection engine, carbon deposits commonly build up on which component because fuel no longer washes past it?

Accepted Answer

Intake valves

Answer

Because GDI/FSI/TSI engines inject fuel directly into the cylinder, intake valves are never bathed in fuel, so oil vapors from PCV accumulate and form carbon deposits.

Question 2

What type of injector technology do high-pressure VW TDI systems use for faster, more precise injection control?

Accepted Answer

Piezoelectric injectors

Answer

Piezoelectric injectors expand instantly when voltage is applied, allowing multiple injection events per cycle with very short opening times for precise fuel metering.

Question 3

What is the role of the fuel pressure sensor (FPS) on the common rail of a VW TDI engine?

Accepted Answer

It signals the ECU to control rail pressure via the high-pressure pump and metering valve

Answer

The FPS provides real-time rail pressure data to the ECU, which adjusts the HPFP metering valve and pressure control valve to maintain target rail pressure.

Question 4

In a VW FSI engine, what low-pressure value does the fuel supply system typically maintain at the high-pressure pump inlet?

Accepted Answer

3–7 bar

Answer

The in-tank pump maintains approximately 3–7 bar at the HPFP inlet to ensure cavitation-free operation and consistent high-pressure output.

Question 5

What VW-specific diagnostic function allows a technician to check the volume balance of individual fuel injectors on a TDI engine?

Accepted Answer

Injector quantity adjustment (IQA) coding

Answer

IQA coding programs the ECU with factory-measured flow correction values for each injector so it can compensate for individual delivery differences.

VW - Volkswagen Certified Mechanic Practice Test

VW - Volkswagen Certified Mechanic Practice Test

VW Fuel Systems & Injection Technology 2