The name 2.0 TDI covers several generations of engine used in particular by Volkswagen, Audi, SEAT and Škoda. They do not all use the same injection system.
Some older 2.0 TDI engines use unit injectors, while other generations are fitted with a Common Rail system. Diagnosis and the injector part number therefore depend directly on the engine code.
Start by identifying the engine generation
- unit injector system;
- Common Rail with piezo injectors;
- Common Rail with solenoid injectors;
- a more recent evolution of the injection system.
The make and the engine size are not enough. The engine code, the VIN and the number marked on the injector remain essential.
1. Delivery drift or excessive return flow
With wear or contamination, a Common Rail injector can develop excessive internal leakage. Too large a share of the fuel then returns through the return circuit.
- hard starting;
- no start when hot or cold;
- rough idle;
- stalling;
- loss of power;
- unbalanced correction values.
2. Contamination of the fuel circuit
Particles, water or impurities can damage the internal components of the injector and of the high-pressure pump.
- check the fuel filter;
- inspect the fuel in the tank;
- check the high-pressure pump;
- check the supply and return lines;
- look for metal particles.
If metal debris is found, fitting a new injector without cleaning out the circuit risks ruining the new part very quickly.
3. A leak at the seal or the seat
Poor sealing between the injector and the cylinder head can allow combustion gases to escape upwards. Black, sticky deposits may then appear around the base of the injector.
- blowing or knocking noise;
- smell of exhaust gas;
- black deposits around the injector;
- gradual loss of sealing;
- injector difficult to remove.
4. A supply or pressure fault
- lift pump;
- tandem pump on certain versions;
- high-pressure pump;
- pressure regulator;
- rail pressure sensor;
- fuel filter;
- air ingress into the circuit.
5. An electrical or connector fault
- injector connector;
- wiring loom;
- condition of the pins;
- continuity of the cables;
- the signal sent by the ECU.
Which symptoms should put you on alert?
- unusual engine knock;
- unstable idle;
- long cranking;
- black, white or greyish smoke;
- loss of power;
- increased fuel consumption;
- engine or glow plug warning light on;
- limp-home mode;
- smell or leak of diesel.
See also our guide to the symptoms of a failing injector.
What checks should be made before replacing an injector?
- full reading of the fault codes;
- monitoring of live engine data;
- analysis of the injection corrections;
- return flow test;
- checking low and high fuel pressure;
- electrical testing of the injectors;
- inspection of the fuel and the filter;
- bench testing if necessary.
How can injection problems be prevented?
- use fuel that meets specification;
- respect the fuel filter replacement intervals;
- maintain strict cleanliness during work;
- prime the circuit correctly after repair;
- diagnose hard starting promptly;
- never ignore a fuel leak.
How do you order the right injector for a 2.0 TDI?
- the engine code;
- the VIN;
- the power output of the vehicle;
- the year of first registration;
- the part number of the removed injector;
- a legible photo of the markings;
- the correction code where present.
Do not order on the strength of the words 2.0 TDI alone. Several incompatible injectors can be offered under that single designation.
FAQ on 2.0 TDI injection faults
Do all 2.0 TDI engines use the same injectors?
No. There are several generations, engine codes, power outputs and injection technologies.
Does a high correction value prove that the injector is faulty?
Not always. It can also be the consequence of a compression, sealing or combustion problem.
Is coding required after replacement?
That depends on the generation and the type of injector. See our article on injector coding.
